(ISSN 0892-1016) Volume 24 Spring -Summer 1990 Numbers 1-2 Contents Letters 1 Winter Roost-site Selection by Urban Merlins ( Falco columbarius). ian G. Warkentin and Paul C. James 5 Evidence for a Fall Raptor Migration Pathway Across the South CHINA Sea. David H. Ellis, Angela K. Kepler and Cameron B. Kepler 12 Roost-tree Characteristics, Food Habits and Seasonal Abundance of Roosting Egyptian Vultures in Northern Spain. Olga Cebaiios and Jose a. Donazar 19 Short Communications Bald Eagle Attacks Osprey Nestling. Stephen P. Flemming and Robert P. Bancroft 26 Orientation of American Kestrel Nest Cavities: Revisited. Thomas G. Balgooyen 27 Cannibalism by Black Kite ( Milvus migrans). A. M. Jones and M. Manez 28 News and Reviews 30 Information for Contributors 39 * **** * **** * ******** * Persons interested in predatory birds are invited to join The Raptor Research Foundation, Inc. Send requests for information concerning membership, subscriptions, special publications, or change of address to Jim Fitzpatrick, Treasurer, 12805 St. Croix Trail, Hastings, Minnesota 55033, U.S.A. The Journal of Raptor Research (ISSN 0892-1016) is published quarterly for $15.00 per year by The Raptor Research Foundation, Inc., 12805 St. Croix Trail, Hastings, Minnesota 55033, U.S.A. Application to mail at second class rate is pending at Hastings, Minnesota, and additional mailing office. Printed by Allen Press, Inc., Lawrence, Kansas, U.S.A. Copyright 1990 by The Raptor Research Foundation, Inc. Printed in U.S.A. THIS PUBLICATION IS PRINTED ON ACID-FREE PAPER. THE JOURNAL OF RAPTOR RESEARCH A QUARTERLY PUBLICATION OF THE RAPTOR RESEARCH FOUNDATION, INC. Vol. 24 Spring-Summer 1990 Nos. 1-2 J. Raptor Res. 24(l-2):l-4 © 1990 The Raptor Research Foundation, Inc. Letters Message from the Past President, February 1990 Dear Friends in RRF, When our Editor, Joe Schmutz, asked if I’d like to include a statement in the spring issue of The Journal of Raptor Research, my first thought was that all I have to say is I’m still relieved to have completed my term as President and pleased to have “passed the torch” to the capable hands of Dick Clark. After a few moments of reflection, however, I decided that there were a number of things I would like to say. Joe may learn not to tempt professors with a free soap box. Since 1975, I have been Treasurer, a Director, President-elect and President of the Raptor Research Foundation, Inc. I’m both pleased and proud to have had the opportunity to serve. The organization has grown in membership and budget, but more importantly, in prestige and maturity. I’m pleased to have been a part of that too. I hope you all are equally pleased, both to be members and to have supported the Foundation. The growth is not over, however, and never will be until all aspects of natural history, physiology, etc. of every raptor is thoroughly understood and until no raptors are endangered. So, I urge you to continue your moral and financial support of our organization; volunteer to serve on a committee, run for an office, and ask your friends to join us. On a final note, I also urge you to become active in environmental protection. The ozone holes are increasing in size, 100 acres of rainforest are lost every minute with still undiscovered species becoming extinct, human populations are increasing, and we continue to suffer air pollution, water pollution and massive soil erosion. Our “leaders,” to avoid facing the inevitable, want to study the situation further. We may be witnessing the best-researched environmental disaster in history. In connection with Earth Day, I’ve been asked to speak on endangered species. My message is that we must act now or we will all be endangered species. Thanks again for your support during my Presidency. Please continue or increase your support of Dick Clark. He will lead us to even more growth. — Gary E. Duke, Past President. 1 2 Letters Vol. 24, Nos. 1-2 President’s Report, January 1990 Happy New Decade! And greetings from your new President. Gary E. Duke was the current President when he asked me to write this as incoming President. This is a very typical gesture for Gary, i.e., passing up an opportunity to see his name and message in print to nudge me to develop the necessary habits for my stint as President of The Raptor Research Foundation, Inc., hopefully for the good of the organization. This not only provides me with the opportunity to laud his and your efforts (not a difficult task at all), but to promote continuity and share some of my ideas of where RRF is strong as well as where we can improve and concomitant with that, some ways that we may accomplish improvements. I shall summarize the 1988-1989 years, i.e., those years of Gary Duke’s term, which might be characterized by the phrase “tightening up.” Gary’s predecessor, Jeffrey L. Lincer, brought a new level of professionalism to RRF and made provision for committees to function formally. Gary established the policy of developing formal calendars, of defining much more formally the roles of officers, and committees via “job descriptions” and added six new committees (By-Laws, Development, International, Long-Range Planning, Membership, Nominating and Rehabilitation). He has also brought into being ad hoc committees. Thus, we now have structure within the RRF which is formal enough that a meaningful organizational chart seems to be in order and is included at the end of this letter. A personal goal of Gary’s (along with others within RRF) has been to broaden the activities of the organization regarding environmental matters that touch raptors either directly, or indirectly. He tried to promote the idea of revising Earth Day, to focus attention, once again, upon our dependence of this limited ecosystem which we call Earth. He informally polled the “top ten” conservation oriented organizations of the U.S. and found that “they did not appear to be very interested.” In spite of this, “ Earth Day 1990’’'’ led by Denis Hayes, the Chairman of the original “ Earth Day 1970,” occurred. This reminded me of a statement made at a conference held at a nearby university on Pennsylvania’s involvement in the Chesapeake Bay “clean up,” i.e., if the people will lead the leaders will follow. Thanks to Gary, RRF was listed as a Co-Sponsor which meant we are on record as supporting the idea and will try to continue to promote the idea. The idea of RRF venturing from the traditional North American sites for an annual conference has been talked about for some time, but by the time you read this it has happened. A major portion of the responsibility for this is borne by Sr. Mario A. Ramos (chairperson, and Director of Mexican Projects for the World Wildlife Fund to whom we also owe thanks for their generous “loan” of Mario Ramos) and Michael W. Collopy (At Large RRF Board member) and Sr. Eduardo E. Inigo-Elias. I would also like to personally thank Sr. Romeo Dominguez-Barradas for showing us Aplomado Falcons. Briefly, 93 scientific papers were presented and about 130 people registered and attended. Registrants included raptor people from Canada, England, France, Germany (West), Mexico, the United States, and Venezuela. Well done Senores! Currently the abstracts are being reprinted so that they and a single page index of the approximately 1 60 authors can be distributed to the International Members of RRF. This was the second joint conference with the World Working Group on Birds of Prey (Western Hemisphere Meeting) and hopefully this cooperation will continue and grow and include other organizations. Along these lines, Lynn W. Oliphant (former Western Canada RRF Board member and formerly Chairman of the RRF Development Committee [this post has been taken over by Walter Crawford] and Lynn has become Chairman of our newly organized Conservation Committee) has been very active in promoting a World Wildlife Fund project to protect the Galakmul Biosphere Reserve in Mexico. This is a 1.5 million acre area of humid tropical forest on the Mexican/Guatemalan/Belize borders. For a mere $25 (tax-deductible in the U.S.) you can ensure the protection of an acre (0.4 ha) of this reserve against future development. Cheques or money orders payable to: World Wildlife Fund can be sent to: Lynn W. Oliphant, Veterinary Anatomy, University of Saskatchewan, Saskatoon, Saskatchewan S7N 0W0, CANADA and it will be forwarded for this project. The donor will receive a certificate for the protection of Tropical Raptors. Of course larger donations are also welcomed! Perhaps RRF, and other raptor organizations, could be active participants in the Third World Congress on National Parks (First held in Grand Teton National Park in 1972, Second held in Bali, Indonesia in 1982) scheduled to be held in Venezuela in January of 1992? For the near future plans are well underway for the 1990 Annual Conference to be held in Allentown, Pennsylvania (October 10-14) and as our 1978 conference there was the largest one in the history of RRF, outside of the “mega-conference” in Sacramento, we are looking for another large and successful meeting there. Again, thanks to Gary and Stuart Porter, RRF was one of only two professional ornithological organizations to respond to the EPA’s Office of Pesticides and Toxic Substances request for comments on their proposal to cancel the registrations of granular pesticides containing carbofuran. RRF has been active in attempts to get the Idaho National Guard and the Department of Interior’s Idaho unit of the Bureau of Land Management to incorporate a comprehensive Environmental Impact Statement into their development plans for the area which includes the Snake River Birds of Spring-Summer 1990 Letters 3 Ann. Conf.Guidelines Awards By-Laws Conservation Development Educational International Long Range Planning Membership Nominating Rehabilitation Resolutions Annual Conference Carbofuran Project Earth Day Project Raptors as Problems Snake River Birds of Prey Problem Spotted Owl Problem Prey Area in toto. Unfortunately Gary’s summarization of the situation in a letter to me dated 21 June, i.e., “the National Guard will continue their development, BLM will do little to interfere, and all of the biologists disagree on what course to follow” seems to be all too true. Gary and I did respond to a kind invitation by Stan Senner, Executive Director of the Hawk Mountain Sanctuary Association and Chairman of the U.S. Section of ICBP (of which RRF is a voting Society Member), to provide RRF input into Subcommittee hearings to authorize appropriations for the BLM for fiscal years 1990-1993. The House did adopt an amendment for their bill which sets down terms and conditions which apply to future uses of public lands by National Guard units. This does not, unfortunately, have bearing on the SRBOPA situation. Membership numbers for the RRF are showing some healthy signs, e.g., the attrition rate has come within the bounds of many other professional organizations, i.e., about 25 percent. The number of international members continues to remain at a healthy level and the Board of Directors and General Membership voted in a plan redistricting Board of Directors to provide greater flexibility so representation on Board might become more equitable with regard to membership distribution in RRF. The plan calls for three Board members representing U.S., one for Canada, two for International membership and then six At-Large Board members who will be without geographic constituencies. This is also designed to increase voting membership by increasing the number of board members that a single member is eligible to vote for each year. The success of this plan relies heavily on an active, timely nomination process which I have asked Gary Duke and James Fraser to co-chair. Publications of the RRF have continued to be a most important visible product and hopefully have contributed to the betterment of life for raptors. Thanks to the long-term efforts and expertise of former RRF President, Richard “Butch” R. Ollendorf RRF has produced a 20- Year Bibliographic Index to publications of the RRF. Also, by the time this is read, RRF will be working with a new editor. It is with warm thanks and wishes that we acknowledge the splendid efforts of Jimmie R. Parrish. Under his editorship RRF publications were moved to Allen Press, several Reports were produced, consistency has been incorporated into RRF publications and the Editor’s responsibility is moving from his capable hands to that of his successor Josef K. Schmutz (Department of Biology, University of Saskatchewan, Saskatoon, Saskatchewan S7N 0W0 CANADA). Jimmie was largely responsible for securing the services of Joe Schmutz. Thank you Jimmie, well done, and welcome aboard Joe! Areas where, it seems to me, we might apply some additional efforts are a) in education, b) involvement and visibility 4 Letters Vol. 24, Nos. 1-2 of the RRF Board and c) interorganizational involvement with those working toward common goals. In the realm of education we have been making some progress, e.g., poster production but perhaps we are ready to take on a formal project involving schools on a pilot basis or perhaps even on a national scale?! An idea might be to hold a poster contest for school children with Raptors in our World or some appropriate theme. Children applying for entry forms might be provided a booklet with basic information on raptors (to be produced as a part of this project) and specifications with regard to the poster dimensions, etc. Prizewinning and Honorable Mention posters might be annually displayed as a part of our conference. Awards might be something like an expense paid trip to some area having special importance with regard to raptors, e.g., the Snake River Birds of Prey Area, Hawk Mountain, the California Condor captive-breeding projects in California or Laurel, Maryland, etc. This would require special funding for the awards which would also be a part of this project. This is just one idea to get you thinking and challenge you to submit an idea of your own. With regard to increasing involvement of the Board it seems only fair that candidates for Board elections must be informed of their expected involvement prior to their becoming Board members. Perhaps all candidates for Board membership should be asked to reply to a question such as, “If elected to the RRF Board how would you increase your efforts to work for the purposes of The Raptor Research Foundation, Inc. ?” This should not be construed as a criticism of past or present Board members but an indication that perhaps the organization could further benefit by increased efforts “across the board.” I have already indicated one area where we might achieve increased interor- ganizational effort and that would be by joining forces with sister organizations and promoting appropriate activities at large meetings such as the one to be held in Venezuela. One of my predecessors, Jeff Lincer, once pointed out in the acknowledgments of one of his publications that we all stand on the shoulders of those before us and, as your new president I will be standing most directly on Jeff and Gary’s shoulders. They have provided solid footing (thank you gentlemen), I only hope that I don’t get “light-headed” from the altitude. With your friendly, constructive criticisms, your suggestions for new endeavors and your willingness to help, our organization will continue to grow in numbers and its positive impact on raptors. With your input we will increase the opportunities for you, the RRF member, to become more involved in the operation of your organization at all levels! If this letter prompts any specific ideas on your part why don’t you drop your respective Board member and me a line about it. As a teacher has no reason for being without students, the organization has no reason for being without its members (and the raptors)! — Richard J. Clark. J. Raptor Res. 24(1 — 2):5— 1 1 © 1990 The Raptor Research Foundation, Inc. WINTER ROOST-SITE SELECTION BY URBAN MERLINS {Falco columbarius ) Ian G. Warkentin 1 Department of Biology, University of Saskatchewan, Saskatoon, SK, Canada S7N 0W0 Paul C. James Museum of Natural History, Wascana Park, Regina, Saskatchewan, SK, Canada S4P 3 V7 Abstract.— Roost-site selection by Merlins ( Falco columbarius ) wintering in the city of Saskatoon, Saskatchewan, Canada, was examined for five winters beginning in November 1983. Forty-one solitary roosts in conifer trees used by 16 different birds were identified through radiotelemetry and chance observations. These roosts were compared with a random sample of 44 conifer trees based on 14 variables at the roost tree and within a 10 m radius of the roost tree. All roosts were in conifer trees that were significantly taller and had a greater crown volume than random trees. Merlins did not use roost trees at random; characteristics most useful in distinguishing roost from random trees were size, distance to the nearest conifer greater than 5 m tall, and the total number of trees greater than 5 m and less than 5 m tall within a 10 m radius. We found no significant difference between roost trees used by males and females. The availability of suitable roosting trees may have been a limiting factor in the colonization of the northern Great Plains by Merlins as a wintering area. Selection de arboles-dormideros por los halcones Falco columbarius, en areas urbanas Extracto. — La selection de arboles-dormideros por los halcones Falco columbarius que pasan el invierno en la ciudad de Saskatoon, Saskatchewan, Canada, ha sido examinada durante cinco inviernos desde noviembre de 1983. Cuarentiun dormideros solitarios en arboles coniferos [“Dicese de arboles y arbustos gimnospermos, de hojas persistentes; . . . como el cipres, el pino y la sabina . . .”] usados por 16 diferentes individuos de la especie estudiada, han sido identificados por medio de radiotelemetria y observaciones casuales (de chance). Estos 41 arboles-dormideros han sido comparados con una muestra al azar de 44 coniferas, en base a 14 variables correspondientes al lugar de los dormideros con un radio de 10 metros. Todos los dormideros considerados han sido coniferas significativamente mas altas y con mayor volumen de copa que cualquiera de las 44 coniferas de la ya mencionada muestra. Los halcones no usaban dormideros al azar; las caracteristicas mayormente consideradas para distinguir dormideros y arboles de la muestra han sido: el tamano, la distancia a la mas proxima conifera de mas de 5 metros de altura, y el total de arboles dentro de un radio de 10 metros. No se encontro diferencias significativas entre dormideros usados por halcones machos y hembras. La disponibilidad de arboles-dormideros adecuados puede haber sido un factor limitante para la colonization de los Grandes Llanos del Norte, como areas de invierno, para los halcones. [Traduction de Eudoxio Paredes-Ruiz] Roosting sites of both communal and solitary roosting birds, have been hypothesized to provide protection from potential predators (Lack 1968), act as information centres (Ward and Zahavi 1973; see Weatherhead 1983, Caccamise and Morrison 1986, 1988 for alternative viewpoints), and provide shelter from inclement weather (Walsberg 1986). Birds wintering in temperate zones may encounter reduced food resources, severe thermal stress, and for diurnal 1 Present address: National Zoological Park, Smithsonian Institution, Washington, DC 20008. species at higher latitudes, an extended, overnight, enforced fast. Thus, selection of night roosts may have a substantial impact on winter survival, espe- cially for individuals within a species of small body size. Several studies have addressed the energetic con- sequences of roost-site selection, focusing on those features of roosts which minimize thermoregulatory costs through protection from radiative heat loss, wind and precipitation. For cavity-roosting species there is a significantly increased air temperature in- side their night roost (Kendeigh 1961, Caccamise 5 6 Ian G. Warkentin and Paul C. James Vol. 24, Nos. 1-2 and Weathers 1977), but not among birds that roost in open vegetation, either with or without other birds in the same roost (Kelty and Lustick 1977, Walsberg and King 1980, Walsberg 1986). Shelter from forced convective heat loss appears to be most important to energy conservation when compared with either lo- cal temperature enhancement or improved radiation balance (Walsberg 1986, Webb and Rogers 1988). In Europe, Merlins ( Falco columbarium } roost both communally and singly in winter, on the ground and in trees (Dickson 1973, Cramp and Simmons 1980, Sys 1982, van Duin et al. 1984). In North America, Merlins have only been observed roosting singly in conifers during winter (Servheen 1985, Ilohn 1986, Warkentin 1986). Although several aspects of the roosting behavior of Merlins have been described previously (Dickson 1973, Sys 1982, van Duin et al. 1984, Servheen 1985, Hohn 1986, Warkentin 1986), there is no quantitative study of roost-site selection. Here, we (1) describe the characteristics of roost-trees and the immediate area surrounding the trees chosen by urban Merlins, and (2) determine whether Merlins choose a particular subset of those conifers available for roosting within the city. We also tested for differences between the sexes in the types of roosts selected. Methods The study area comprised the city of Saskatoon, Sas- katchewan, Canada (52°07'N 106°38'W), at the northern edge of the Great Plains of North America. Saskatoon has a dry continental climate; mean monthly temperatures (°C) in the city during the 5 years of study were: November — 8.3, December — 12.2, January —12.6, February —11.6. The terrain outside of the city is typical of the Aspen Parklands region (Harris et al. 1983), with large sections of arable land in gently undulating to rolling topography, dotted with small ponds and Trembling Aspen ( Populus tremuloides ) stands. Except for areas immediately adjacent to the South Saskatchewan River, which bisects Saskatoon, most of the trees and shrubs in residential areas of the city were planted (for details of neighborhood age and species composition of the vegetation, see Warkentin and James 1988). Roosts were located as part of a study conducted from 1983 to 1988 on the winter ecology of Merlins resident m Saskatoon (Warkentin et al., 1990, Warkentin and Oli- phant, in press, Warkentin and West, 1990). We used two techniques to identify roost trees: chance observations of unmarked birds entering a roost at dusk, and following radio-tagged birds to their nighttime roosts. Forty-one roosts, occupied by 16 different birds were included in these analyses. In an effort to approach statistical inde- pendence, each roost was only used once in the analysis with nine of 16 (56%) birds contributing one observation, 5 birds contributing three observations, and single birds providing 7 and 10 observations each. The roost site was defined as the roost tree, and a cir- cular plot of 10 m radius centered on the roost tree. Mea- surements of roost-tree heights were made at most within 18 months of their use, but usually within 4 months (i.e , the following summer). All other measurements were made in April 1988 when random sites were selected and mea- sured. There may have been minor changes in some of the variables included between the time the roosts were used and when the measurements were taken. However, be- cause of the nature of the variables considered (distances and numbers of trees), we suggest that these changes were likely minimal and had little impact on the overall results of our analyses. Heights were measured to the nearest 0.5 m using a clinometer. Compass bearings to the nearest building (di- rected at the closest part of that building) were taken to assess the potential influence of buildings on Merlin roost- ing behavior. Shrub cover was estimated visually and cat- egorized as: 0, <5%, 5 to 25%, or >25%. Vertical distri- bution of roost tree crown volume was estimated using measurements of tree height, distance from the ground to the lowest live branch, and radius of the crown at the lowest live branch (Mawson et al. 1976). Crown shape was compared to the 15 possible crown shapes described by Mawson et al. (1976) and assigned to that which was the best fit. We calculated the crown volume for 2 m height classes of each tree up to 20 m, using the equation ap- propriate for the crown shape. We selected a random sample of potential roost trees from among the conifers in the city to test for the selection of roosts by Merlins. Because trees in the city were planted as neighborhoods were constructed, neighborhood age re- flects the extent of tree growth. Therefore, using city rec- ords, we divided the city into strata on the basis of age and residential/nonresidential criteria, and selected a ran- dom sample from these habitats in proportion to their use for roosting by wintering Merlins. Although trees used by Merlins for nighttime roosts were generally conifers greater than 10 m tall (Warkentin 1986, and see results), Merlins in this population have used trees only 7 m high (War- kentin, pers. obs.). Consequently, w r e restricted the random sample to conifer trees at least 6 m tall in order to eliminate shorter trees from the sample that would not be selected for roosting by Merlins. Street intersections, within regions of the city which matched the description of strata occupied by Merlins, were assigned numbers. Using a random num- bers table, the location of sites to be visited were generated and the conifer tree nearest the centre of the designated intersection was measured for the same variables as roost trees. The 14 variables considered in the discriminant function analysis (DFA) are listed in Table 1 . Some of the variables chosen for analysis were highly correlated, suggesting that they measured the same or similar aspects of the environ- ment. When there was a high degree of correlation between two variables (r > 0.7), only one of the variables (that which could be most readily used in a biological expla- nation of the results) was included in subsequent analysis Data on 10 of the 14 variables (Table 1, wfith CONHT>5, CONHT<5, DECHT>5, DECHT<5 excluded due to Spring-Summer 1990 Roost-site Selection by Merlins 7 Table 1. Descriptions of habitat variables used in the analysis of Merlin roost-site selection. Shrubs are defined as woody vegetation with multiple stems at ground level; trees have a single woody stem. Mnemonic Description TREE TREEHT DBH CONHT>5 DECHT>5 CONHT<5 DECHT<5 TREEHT>5 TREEHT <5 SHRUB NEARCON DISTBLDG DISTPOLE DISTROAD Roost-tree species. Height of roost tree in metres. Diameter at breast height of roost tree in centimetres. Number of coniferous trees >5 m tall in the 10 m radius plot. Number of deciduous trees >5 m tall in the 10 m radius plot. Number of coniferous trees <5 m tall in the 10 m radius plot. Number of deciduous trees <5 m tall in the 10 m radius plot. Number of trees >5 m tall in the plot (CONHT>5 4- DECHT>5). Number of trees <5 m tall in the plot (CONHT<5 + DECHT<5). Percentage of plot covered by shrubs, in one of four categories: 0%, <5%, 5 to 25%, and >25%. Distance from the roost tree to the nearest coniferous tree >5 m tall. Distance from the roost tree to the nearest building. Distance from the roost tree to the nearest power pole or lamp standard. Distance from the roost tree to the nearest roadway. cross correlation with TREEHT <5 and TREEHT>5) measured at roost and randomly selected trees were com- pared initially using univariate analysis of variance. We then performed a multivariate stepwise DFA (Dixon and Brown 1979) to determine differences in habitat structure around roost trees and randomly selected trees. Canonical correlation analysis, based on the most powerful discrim- inating variables, resulted in a classification distribution for all trees measured. The resulting jackknifed classifi- cation distribution was tested for chance correctness using Cohen’s Kappa statistic (Titus et al. 1984), which assesses how well the discriminant analysis improves the classifi- cation beyond chance. Crown profiles within roost and random tree groups were combined to give average profiles and the resulting values were tested for differences between groups using multivariate analysis of variance (MANO- VA; SAS Proc GLM, SAS Institute 1985). We used Ra- leigh’s R to determine the significance of differences in the mean bearings of the building nearest to the roost tree. Results As reported elsewhere for this population (War- kentin 1986, Warkentin and West, 1990), all of the Merlins observed spent winter nights alone in co- nifer trees (White Picea glauca and Blue Spruce P. pungens). The means of the habitat variables from 41 occupied roosts and 44 randomly selected trees are in Table 2. TREEHT and DBH were the only variables that demonstrated a statistically significant difference between the two groups. Even when trees m the random sample shorter than the smallest oc- cupied roost tree included in these data (10 m) were omitted from the analysis, the difference between groups in TREEHT was significant (14.5 ± 2.3 and 12.8 ± 1.9 m for occupied and random sites, respectively; F = 10.97; df = 1 ,72; P < 0.01). Twelve trees in the random sample were less than 10 m tall but only one was less than 7 m tall. In the multi- variate analysis, the stepwise DFA selected TREEHT, NEARCON, TREEHT<5, and TREEHT>5, as being most important in distin- guishing between roost trees and randomly selected trees. The analysis correctly classified 77% of all sites as to their use, 31 (76%) of 41 occupied roosts and 34 (77%) of 44 randomly selected trees were correctly classified; significantly better than expected by chance (Z = 4.875, P < 0.001). The mean com- pass bearing to the nearest building was not signif- icantly different from random for either the roost trees or randomly selected trees (occupied: Raleigh’s R = 5.41, P > 0.20; random trees: R = 3.48, P > 0.50, respectively). Crown profiles of roost trees were significantly different from those of random trees (Fig. 1; MAN- OVA: Wilk’s lambda = 0.75, F = 2.45, df = 10,74, P < 0.05). This overall result was due to signifi- cantly greater volumes ( P < 0.05) for roost trees at all levels except 2-4 m, 1 6- 1 8 m, and 1 8-20 m where there was no statistical difference, and the 0-2 m level where random trees had greater volumes than roost trees. Male Merlins are significantly smaller than fe- males; among wintering adults males are, on aver- 8 Ian G. Warkentin and Paul C. James Vol. 24, Nos. 1-2 Distance above ground (m) Figure 1. Crown volumes (m 3 ) of occupied roost trees (N = 41) and randomly-selected trees (N = 44), at 2-m intervals. age, 90 g lighter than females (Warkentin et al., 1990). Based on the hypothesis that Merlins are subject to energetic stress while wintering in Sas- katoon, and that the use of more protected roosts increases an individual’s chance of survival by re- ducing energetic stress, we predicted that roost sites offering greater protection might be selected more often by males than females. A comparison of roost types for males and females by DFA showed no significant differenc'd when the same variables from the initial comparison were tested (canonical dis- criminant analysis, SAS Proc GANDISC: Wilk’s lambda = 0.71, F = 1.25, df = 10,30, P = 0.30). Discussion Reduced convective heat loss inside versus outside of the roost has been found in studies of avian noc- turnal roosts (Buttemer 1985, Walsberg 1986, Webb and Rogers 1988). Given such findings, we predicted that any substantial sheltering effect from surround- ing buildings would be reflected in a significant mean bearing from roost tree to nearby buildings, similar to that of the prevailing winds. Despite prevailing westerly winds, however, there was no apparent use of buildings to provide shelter as indicated by ran- dom compass bearings to nearby buildings for both Spring-Summer 1990 Roost- site Selection by Merlins 9 Table 2. Sample means, standard deviations and coefficients of variation (in parentheses) of habitat variables for winter roosts occupied by Merlins in Saskatoon, Saskatchewan, between 1983 and 1988 (N = 41), and randomly-selected trees in the city of Saskatoon (N = 44). Variable Occupied Random E(ANOVA) p* TREEHT (m) 14.3 ± 2.3 (0.16) 11.6 ± 2.5 (0.22) 28.55 <0.001 DBH (cm) 39.5 ± 9.0 (0.23) 31.2 ± 9.2 (0.29) 17.82 <0.001 SHRUB 1.8 ± 0.8 (0.43) 1.8 ± 0.9 (0.48) 0.11 ns NEARCON (m) 6.6 ± 5.2 (0.79) 8.3 ± 7.6 (0.91) 1.47 ns DISTBLDG (m) 9.8 ± 9.3 (0.95) 9.5 ± 13.2 (1.39) 0.02 ns DISTPOLE (m) 19.9 ± 9.4 (0.47) 18.9 ± 10.4 (0.55) 0.21 ns DISTROAD (m) 9.6 ± 6.7 (0.69) 8.7 ± 6.8 (0.79) 0.40 ns TREEHT<5 0.9 ± 1.4 (1.54) 0.6 ± 1.0 (1.63) 1.01 ns TREEHT>5 3.0 ± 2.2 (0.71) 3.2 ± 2.5 (0.80) 0.05 ns a Not significant at 0.05 level. roost and random trees analyzed. Despite the ab- sence of a major sheltering influence from outside of the roost tree, Merlins usually roosted on the leeward side of roost trees, hopping among the branches before choosing their roost perch (War- kentin, pers. obs.). Among the variables we considered, the features of primary importance governing the selection of a roost tree by Merlins wintering in Saskatoon ap- peared to be those of the tree itself, rather than its surroundings. This was apparent in both the uni- variate analysis (Table 2) and the stepwise DFA in which tree height (TREEHT) was the first variable chosen. The predictive power of the discriminant analysis was based, however, not only on tree height, but also on the distance to the nearest conifer from the roost tree (NEARCON), as well as the number of trees less than, and greater than, 5 m tall within the plot (TREEHT<5 and TREEHT>5). The importance of tree height to roost-site selection was reflected in the comparison of crown volumes for occupied and random trees. Taller trees had greater crown volumes, which was also' likely related to the amount of wind reduction experienced by a bird in its roost, as well as affecting the extent of radiative heat loss through open areas of the canopy above the roost perch. Nearby conifers also may provide added protection from wind and increase the shel- tering effect of the roost tree. We found that occupied roosts had a smaller NEARCON distance than did random trees; however, the difference was not sta- tistically significant in the univariate analysis (Table 2). Our inability to detect a significant difference between groups for this distance may reflect our sample size. Similarly, more trees in the vicinity of the roost would be expected if there was a benefit from decreased wind speed in the roost. It is difficult to determine the importance of pre- dation as a selective pressure for roost-site choices. Although it has been alluded to in the literature (Lack 1968, Walsberg and King 1980), there has been little work in this area. For Merlins resident in urban areas, taller roost trees may be important in reducing mammalian predation, particularly by domestic cats, which are common in the city and often forage at night. Also, Great Horned Owls ( Bubo virginianus ) were observed in the city during each winter of this study. One radio-tagged yearling male 10 Ian G. VVarkentin and Paul C. James Vol. 24, Nos. 1-2 disappeared overnight and apparently was killed while roosting. The bird was radio-tracked to the roost tree at dusk, its position confirmed that night, and monitoring resumed before dawn the next morn- ing when the radio was discovered on the ground underneath the tree. In the absence of other noctur- nal avian predators, the lack of remains beneath the roost, except for some tail feathers attached to a piece of flesh, suggested predation by an owl. One might predict that repeated use of the same roost tree could be dangerous, because predators may be able to detect roosting birds by the accumulating feces and regurgitated pellets. There was no appar- ent pattern among radio-tagged Merlins in the re- peated use of individual roosts; one adult female used the same roost site continuously for a period of 33 nights, yet four other adults were much more varied and used 6 different roosts in an 11 -night period, 3 roosts in 11 nights, 10 roosts in 47 nights, and 4 roosts in 51 nights of monitoring. Yearlings (N = 3) varied in their roosting behavior from extended use of the same tree (one roost for 7 nights), to at least 4 roosts in a 10-night period. In some cases, differing patterns of winter roost use may reflect the level of commitment to a former or future breeding site within the winter home range (Warkentin and Oliphant, in press), habitat use during the active phase prior to roost entry, or perhaps experience with predators. There is little overlap between day- time perches and nighttime roosts, and little ten- dency to use night roosts for hunting during the day. On average, only 19% of the daylight phase was spent within 250 m of the main roost by radio-tagged Merlins (Warkentin and Oliphant, in press). Thus, local prey availability has little apparent influence on the selection, or consistency of use, of night roosts. The phenomenon of nonmigratory individuals among populations of Merlins breeding in the north- ern Great Plains is a recent development (James et al. 1987). Traditionally, all birds from northern populations were migratory. However, there is now an apparent dichotomy with rural populations re- maining strictly migratory and many urban popu- lations displaying partial migration. Because all birds in this and other studies of North American Merlins appear restricted to the use of conifers for winter roosts, the availability of roosts may have been one limiting factor in the colonization of the northern Great Plains as a wintering area. Roosting in co- nifers provides a savings of about 6% of the total daily energy expenditure for Merlins wintering in Saskatoon (Warkentin and West, 1990). Consider- ing that most conifers in the city are the result of human planting beginning 60-80 years ago, trees large enough to provide sufficient protection from the elements in winter may only recently have be- come available. Several studies have suggested that the availability of roosting sites may influence the winter distribution of some species (see Eiserer 1984 for review). Mills (1975) found that the distribution of American Kestrels {F. sparverius ) wintering in Ohio was closely linked to the availability of old buildings or other such sheltered roosts. The rela- tively recent availability of conifers may, in part, explain the northward expansion of the Merlin’s wintering range. However, it also raises the question of why communal roosting evolved in Palearctic pop- ulations of Merlins (where there has been some spec- ulation that roost sites may be limiting, at least in some locations; Sys 1982), but not in an apparently similar local situation in North America, where Merlin density also may have been limited by roost availability. Acknowledgments We thank Bill Iko for his help in data collection. Bob Clark and Bob Bailey provided helpful comments during the analysis of these data. Keith Bildstein, Gary Bortolotti, Lynn Oliphant, and Phil Schempf commented on early drafts of the manuscript. Funding was supplied by the Natural Sciences and Engineering Research Council of Canada, the University Research Support Fund of the Canadian Wildlife Service, the Frank M. Chapman Fund of the American Museum of Natural History, the Ca- nadian Plains Research Centre, and a University of Sas- katchewan Graduate Scholarship to the senior author Dave Ankney and the Department of Zoology, University of Western Ontario provided facilities and resources to the senior author during preparation of this manuscript. Literature Cited Buttemer, W.A. 1985. Energy relations of winter roost- site utilization by American Goldfinches ( Carduehs tris- tis). Oecologia 68:126-132. Caccamise, D.F. and D.W. Morrison. 1986. Avian communal roosting: implications of “diurnal activity centers.” Am. Nat. 128:191-198. and . 1988. Avian communal roosting a test of the “patch sitting” hypothesis. Condor 90:453- 458. AND WAV. Weathers. 1977. Winter-nest mi- croclimate of Monk Parakeets. Wilson Bull. 89:346- 349. Cramp, S. and K.E.L. Simmons. 1980. The birds of the western Palearctic. Vol. II. Oxford University Press, London. Spring-Summer 1990 Roost-site Selection by Merlins 11 Dickson, R.C. 1973. A Merlin roost in Wigtownshire. Scot. Birds 7:288-292. Dixon, W.J. and M B. Brown. 1979. Biomedical com- puter programs, P-series. University of California Press, Berkeley. ElSERER, L.A. 1984. Communal roosting in birds. Bird Behav. 5:61-80. Harris, W.C., A. Kabzems, A.L. Kosowan, G.A. Padbury and J.S. Rowe. 1983. Ecological regions of Saskatchewan. Saskatchewan Parks and Renewable Resources, Tech. Bull. No. 10. Regina, Saskatchewan. Hohn, E.O. 1986. Roosting habits of an urban Merlin. Blue Jay 44:194-196. James, P.C., A.R. Smith, L.W. Oliphant and I.G. Warkentin. 1987. Northward expansion of the win- tering range of Richardson’s Merlin. J. Field Ormthol. 58:112-117. Kelty, M.P. AND S.I. Lustick. 1977. Energetics of the Starling ( Sturnus vulgaris) in a pine woods. Ecology 58: 1181-1185. KENDEIGH, S.C. 1961. Energy of birds conserved by roosting in cavities. Wilson Bull. 73:140-147. Lack, D. 1968. Ecological adaptations for breeding in birds. Methuen, London. Mawson, J.C., J.W. Thomas and R.M. DeGraff. 1976. Program HTVOL: the determination of tree crown volume by layers. USDA For. Serv. Res. Paper NE-354. Amherst, MA. Mills, G.S. 1975. A winter population study of the American Kestrel in central Ohio. Wilson Bull. 87:241- 247. Sas Institute Inc. 1985. SAS user’s guide: statistics. 1985 edition. SAS Institute, Cary, SC. Servheen, C. 1985. Notes on wintering Merlins in western Montana. Raptor Res. 19:97-99. SYS, P. 1982. Observations at a communal roost of win- tering Merlins. Wielewaal 48:360-367. Titus, K., J.A. Mosher and B.K. Williams. 1984. Chance corrected classification for use in discriminant analysis: ecological applications. Am. Midi. Nat. 111. 1-7. VAN Duin, G., F. Vogelzang, R. Sjouken, R. Stet, S. Schoevaart and J. Buker. 1984. Communal roost of Sparrowhawk Accipiter nisus, Merlin Falco colum- barius, and Hen Harrier Circus cyaneus. Limosa 57:97- 103. Walsberg, G.E. 1986. Thermal consequences of roost- site selection: the relative importance of three modes of heat conservation. Auk 103:1-7. and J.R. King. 1980. The thermoregulatory significance of the winter roost-sites selected by Robins in eastern Washington. Wilson Bull. 92:33-39. Ward, P. and A. Zahavi. 1973. The importance of certain assemblages of birds as “information centres” for food finding. Ibis 115:517-534. Warkentin, I.G. 1986. Factors affecting roost depar- ture and entry by wintering Merlins. Can. J. Zool. 64 1317-1319. AND P.C. JAMES. 1988. Nest-site selection by urban Merlins. Condor. 90:734-738. , , and L.W. Oliphant. 1990. Body size, age structure, and partial migration of urban Merlins. Auk 107:25-34. and L.W. Oliphant. In press. Habitat use and foraging behaviour of urban Merlins ( Falco columbar- ius ) in winter. J. Zool. (Lond.). and N.H. West. 1990. Ecological energetics of wintering Merlins ( Falco columbarius) . Physiol. Zool 63:308-333. WEATHERHEAD, P.J. 1983. Two principal strategies in avian communal roosts. Am. Nat. 121:237-243. Webb, D.R. and C M. Rogers. 1988. Nocturnal energy expenditure of Dark-eyed Juncos roosting in Indiana during winter. Condor 90:107-112. Received 4 December 1989; accepted 19 February 1990 J. Raptor Res. 24(1-2):12-18 © 1990 The Raptor Research Foundation, Inc. EVIDENCE FOR A FALL RAPTOR MIGRATION PATHWAY ACROSS THE SOUTH CHINA SEA David H. Ellis U.S. Fish and Wildlife Service , Patuxent Wildlife Research Center, Laurel, MD 20708 Angela K. Kepler and Cameron B. Kepler Southeast Field Station, U.S. Fish and Wildlife Service, School of Forestry Resources, University of Georgia, Athens, GA 30602 Abstract. — While conducting seabird surveys along the cruise track of the Soviet oceanographic Research Vessel Akademik Korolev in the South China Sea in late October, 1988, we encountered about 150 land birds, including about 40 raptors. Most of the raptors were small accipiters, but we also recorded small numbers of Peregrine Falcons ( Falco peregrinus) and Oriental Scops Owls (Otus sunia). We saw most of the raptors during a 3-day period in a restricted area ca 350 km southeast of the southern tip of the Indo-China Peninsula. The observations suggest that a significant raptor migration corridor exists between Viet Nam and Borneo. The behavior and body condition of the diurnal raptors suggest that they were in good health and were making extensive use of the ship for perching, roosting, and hunting. Evidencia de una ruta de migracion otonal de aves de rapina atravesando el Mar del Sur de China Extracto. — Mientras conduciamos un estudio de las aves marinas en la ruta de la embarcacion sovietica de investigation oceanografica Akademik Korolev, en el Mar del Sur de China a finales de octubre de 1988, hemos hallado 150 aves de tierra, incluyendo 40 aves de rapina. La mayoria de estas ultimas han sido pequenos gavilanes ( Accipiter spp.), pero tambien hemos registrado unos cuantos halcones peregrinos ( Falco peregrinus ) y buhos ( Otus sunia). Hemos observado la mayoria de las aves de rapina durante un periodo de tres dias en una area restringida, aproximadamente a 350 km al sudeste del extremo sur de la Peninsula Indochina. Las observaciones sugieren que existe una ruta de significativa migracion de este tipo de aves entre Viet Nam y Borneo. Por la conducta y condiciones fisicas de estas aves de rapina diurnas concluimos que estas se encontraban con buena salud y hacian uso extensivo de la embarcacion para posarse, para dormir, y para cazar. [Traduction de Eudoxio Paredes-Ruiz] The most noteworthy areas where birds of prey aggregate during fall migration are in Middle Amer- ica, Europe, and the Middle East (Kerlinger 1989). Except for the Straits of Malacca (Robinson 1927), migration corridors for raptors in eastern Asia are poorly known (Wetmore 1926, Delacour 1947, McClure 1974, Medway and Wells 1976); however, important flights for non-raptors are known from Japan and eastern China south through the Phil- ippine Islands, with another corridor down the Ma- lay Peninsula (McClure 1974, Medway and Wells 1976). Evidence for raptor migration across the South China Sea is very limited. Biologists from the Chinese Academy of Science and the Beijing Natural History Museum (Anon. 1974) encountered unspecified numbers of two species of raptors among 44 species of land birds noted during 1974 surveys of the islets m the northern South China Sea (outside our study area). Recently Simpson (1983a, 1983b) encoun- tered hundreds of migrant land birds and raptors of three species at the Tembungo oil platform, west of the northern tip of Borneo (Fig. 1) during the fall migration of 1981. His most commonly observed raptor, the Japanese Sparrowhawk ( Accipiter gu- laris), was seen regularly from late September to mid October. Although Simpson reported his observa- tions as evidence of a passage directly over the South China Sea, his location near Balabac Strait suggests that the migrants he observed were moving south and west from the Philippines. McClure (1974) as- serts that many migrants enroute to Borneo through the Philippines fly west from Palawan, then south to Borneo. More recently, however, Simpson (Wells, pers. comm, and in press) provided more conclusive evidence for a direct South China Sea crossing by migrant land birds. He reported a substantial fall movement of land birds (36 species) including at 12 Spring-Summer 1990 South China Sea Raptor Migration 13 Figure 1. Geography of the southern half of the South China Sea showing bird survey locations. Numbered segments are bird survey locations for R.V. Akademik Korolev, 23-31 October 1988. least two species of diurnal raptors and the Oriental Hawk-owl ( Ninox scutulata) from the Terengganu oil field (05°25'N, 105°13'E, Fig. 1). This location is approximately 200 km east of the Malay Penin- sula. The geography of the land masses surrounding the South China Sea form three natural funnels that should concentrate migrant raptors into three pri- mary corridors. First, migrants moving south from Burma and western Thailand should flow onto the Malay Peninsula. Many of those in eastern China could “island-hop” south through the Philippines, and those moving south into the Indo-China Pen- insula would naturally converge south of the Me- kong River delta on Mui Bai Bung cape. From the Indo-China Peninsula, those traveling overland must fly north and west into Thailand. Those capable of a short oversea migration could fly southwest toward 14 Ellis et al. Vol. 24, Nos. 1-2 Table 1. Raptor and other land bird counts along R. V. Akademik Korolev cruise track in the South China Sea, October 1988. 1 ’ 2 Taxon or Group Conserva- Minimum tive Count Count Segments 1-7 (Oct. 23- 24) Balabac Strait and offshore Borneo Raptors 0 0 Non-raptors Segments 8-19 (Oct. 25 1 -29) South-central 1 South China Sea Raptors: Accipiter sp. 19 30 Eagle/kite 1 1 Peregrine Falcon 3 3 Oriental Scops Owl 2 2 Non-raptors: Barn Swallow 14 29 Other non-raptors 27 Segments 20-30 (Oct. 29-31) Near southern tip of Malay Peninsula 31 Raptors: Accipiter sp. 3 3 Oriental Scops Owl 0 1 Non-raptors: Barn Swallow 5 10 Other non-raptors Totals for Segments 1-; 9 30 (Oct. 23-31) 10 Raptors: Diurnal raptors 26 37 Owls 2 3 Non-raptors: Barn Swallows 19 39 Other non-raptors 37 42 1 Because accurate bird counts were sometimes difficult to obtain for stationary watches (i.e., some birds remained aboard ship for an extended period), we report both the minimum number of birds observed (based on subtractive values) and a conservative number (based primarily on new arrivals). The actual number is believed to be about 20% higher than the conservative count. 2 Cruise track segment locations are illustrated in Figure 1. the Malay Peninsula. Those capable of a long over- water passage could fly south toward Borneo and the other Greater Sunda Islands. Except for birds encountering the Natuna Islands, this route would require a single crossing of more than 800 km. The first two routes, down the Malay Peninsula and island hopping through the Philippines, are im- portant corridors for fall migrants (Wetmore 1926, McClure 1974, Ng 1978). In addition, McClure (1974) and Hails (1987) present maps showing a minor pathway extending southwest from Indo- China across the Gulf of Thailand to the Malay Peninsula. However, none of these authors report the pooling of migrants on the tip of the Indo-China Peninsula or any other likely point of departure north of the South China Sea. For raptors, we lack published evidence for routes south or southeast from the Indo-China Peninsula directly across the South China Sea. The only published suggestion of such a raptor migration corridor is Simpson’s (1983a) observations of small numbers of diurnal raptors (3 species) and 1 or 2 individual owls near the north- eastern tip of Borneo and, therefore, on a migration route already recognized by McClure (1974) as im- portant in the passage of birds, not across the South China Sea to Borneo, but through the Philippines to Borneo. Study Area and Methods We observed raptors and other migrant land birds dur- ing our 23-31 October 1988 indirect passage (Fig. 1) from the Balabac Strait (southwestern Philippine Islands) to Singapore, on the Soviet Research Vessel Akademik Ko- rolev (7000 tons, 124 m length). We provide greater detail on the non-raptors in a companion paper (Ellis et al., in press). While the ship was in transit, we observed birds during dawn to dusk watches from the flying bridge of the ship (12 m above sea level). During the 3-day period while the ship was anchored or drifting without power (Fig. 1, station 13; 06°0TN, 106°55'E), we conducted walking inspections (usually at half-hour intervals) during daylight hours and searched the ship each night by flash- light to count roosting raptors. Juveniles of several species of small Asian accipiters are extremely difficult to identify. For this reason, we grouped all of those we visually observed as “small juvenile accip- iters”. However, four were captured by hand, two while roosting on the ship’s rigging. We used wing formulae and size (King and Dickinson 1975) to tentatively classify them. Results and Discussion During our 9-day passage through the South China Sea, we encountered about 150 land birds, including 40 raptors (28 by minimum count; Table 1). Almost all were Asian migrants that winter (at least in part) south of the South China Sea. Most of the land birds, and nearly all of the raptors (Table 1), visited the ship during the 3-day period while we were an- chored or drifting (Fig. 1, station 13) south of Indo- China. The presence of these birds at this location suggests that they were in passage across the South Spring-Summer 1990 South China Sea Raptor Migration 15 China Sea from Indo-China to the Greater Sunda Islands. The low numbers for raptors seen before arriving at, and after leaving, this location (Table 1) reinforces the hypothesis that this spot lies on a rather narrow migratory corridor. However, Simp- son’s (Wells, in press) 1982 observations from the Terengganu oil field (Fig. 1) suggest that the path- way may be wider than we detected. The fact that few birds were observed while in transit may reflect a tendency to avoid moving ships. Of all land birds seen (Table 1), a high proportion (over 30%) were raptors. Most were small accipiters, but three were peregrine falcons. We also encountered one eagle/ kite and two to three Oriental Scops Owls, including one that died on board (USNM No. 607190). Most of the accipiters were juveniles. Four of these were captured and identified by wing formulae (King and Dickinson 1975): three as Japanese Sparrow- hawks (No. 1: tail 116.4 mm, wing chord L 161 mm, R 159 mm; No. 2: 128 g, tail 121 mm, wing chord L 180.5 mm, R 180 mm; No. 3: tail 114.6 mm, wing chord L 164 mm, R 164 mm) and one as a Shikra ( Accipiter badius) (129 g, tail 130 mm, wing chord L 186 mm, R 185 mm). All four were in good flesh and flew well upon release. Because Shikras are not believed to migrate over the South China Sea (Brown and Amadon 1968) and were unreported by Simpson (1983a, and D. R. Wells, pers. comm.) for other regions of the South China Sea, we present our identifications as tentative. However, adult accipiters are distinguishable in the field: we identified two as male Japanese Spar- rowhawks and one that was clearly seen as a male Shikra. In addition, although we know of no evidence for migratory movements of the Crested Goshawk ( Accipiter trivirgatus) , we clearly observed two near- by birds (Fig. 1 , station 13). The bold, high contrast, ventral barring and streaking, left little doubt that they were adults of this species. However, both birds were observed only in flight, so we had little op- portunity to and failed to see the diagnostic occipital crest. The number of birds we encountered (Table 1) is small when compared with record counts for well- known migrant concentration areas elsewhere around the world. However, our visit was brief and probably too late for detecting the peak of the accipiter mi- gration. Simpson (1983a) reported his highest counts for Japanese Sparrowhawks near northeastern Bor- neo around 10 October. Further, migrating raptors are most often counted where local topography en- courages them to aggregate. By contrast, we were on the open sea where birds are less likely to con- centrate. Considering these factors and Simpson’s (Wells, in press) observations, it seems likely that adequate spatial and temporal sampling will reveal thousands of accipiters and a few other raptors mov- ing south from Indo-China across the South China Sea. Although our records and Simpson’s (Wells, in press) 1982 observations are sufficient to demon- strate that a considerable raptor migration crosses the South China Sea, we should mention two alter- nate hypotheses that may explain the presence of the birds we observed. First, our passage occurred when Typhoon Ruby was ravaging the Philippine Islands (Anon. 1989). Some of the birds we observed may have been forced out to sea or shunted away from their normal migration route by the storm. The storm hypothesis may also explain our anomalous observations of “non-migratory” Shikras and Crest- ed Goshawks and migratory Oriental Scops Owls 350 km from land. A second alternate hypothesis is that some of the raptors were not in passage at all, but were foraging at sea during the fall land bird migration (see Ker- linger 1989 for pertinent references). During the 3-day waiting period (Fig. 1, station 13), we re- corded raptors perching for extended periods, roost- ing nightly on the ship, and engaging in at least 21 hunting forays (Table 2). Of 14 forays for which the outcome was known, 13 (93%) were successful. Some accipiters even used the ship’s deck lights to forage at night. We gathered remains of 20 prey during the 3-day period. Two species, the Barn Swallow ( Hirundo rustica) and the Brown Shrike (Lanins cristatus ) suffered heavy mortality from pre- dation. Of at least 14 Barn Swallows observed from 25-29 October, at least 7 were recovered as prey. Even more significant, at least 5 of at least 6 Brown Shrikes became prey. Simpson’s (1983a and Wells, in press) observations of raptor behavior at both oil fields led him to conclude that Japanese Sparrow- hawks were hunting and “commuting between near- by rigs.” Our observations confirm that the raptors were opportunistically using our stationary ship for perching, roosting, and hunting. When the ship was under power, however, none of the raptors perched for long and none roosted on the ship. Flight direction for the raptors and other birds may give additional evidence for each hypothesis. If migrating while avoiding the typhoon, birds would Table 2 Predation episodes and prey remains aboard R. V. Akademik Korolev, South China Sea 27-29 October 1988 16 Ellis et al. Vol. 24, Nos. 1-2 Cfl Z w a a o U ' Cfl U co P « {55 P « O £ w ca * rt Pi Pl. 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Vegetation in the Pyrenees is predominantly for- est [Scots pine {Pinus sylvestrys), beech {Fagus sylvayica) and oak {Quercus spp.)] while in the Ebro valley herba- ceous pseudosteppe vegetation and cereal cultures predom- inate. 19 20 Olga Ceballos and Jose A. DonAzar Vol. 24, Nos. 1-2 Table 1. Characteristics of Egyptian Vulture roosts. The number of checks and the information (number of Egyptian Vultures, date, % immatures) obtained from the checks when a large number of birds was seen is detailed. For other species seen regularly the maximum number observed is detailed. Roost 1 2 3 4 5 6 Substrate Pines a Pines b Pines c White poplar Cliff Pines 3 Number of checks 42 10 8 2 14 4 Max. no. Egypt. Vult. 138 43 52 72 14 8 Date 29 July 1988 29 July 1988 15 July 1987 6 July 1988 7 July 1987 7 July 1987 % immatures Other species 27.5 18.6 19.6 28.3 5.1 25.0 Griffon Vulture 210 — — — 26 — Black Kite 70 — — — — — Red Kite 25 8 3 — — — Raven 100 — 60 — — — a Pinus halepensis, b = P. sylvestris, c = P. nigra. Roost tree characteristics were studied in 4 large roosts using comparisons with control trees. Roost trees were considered to be those under which Egyptian Vulture droppings, feathers and pellets could be found simulta- neously. Control trees were chosen by random selection in the roost area. All trees with a diameter at breast height (DBH) >15 cm were included in the analysis. The fol- lowing 5 variables were evaluated for each roost and con- trol tree: 1) Maximum DBH (cm); 2) Height (m) measured with optical instruments; 3) Number of trees (>15 cm DBH) in a 10 m radius; 4) Foliage cover (classified on a scale of 1 to 5; a value of 1 represented a tree with green leaves on every branch and a value of 5 represented a defoliated (dead) tree), 5) Percentage of open space around the maximum di- ameter of the crown of the tree. Closed space is taken to be when the crowns of neighboring trees were closer than 2 m to that of the tree measured. Values for roost and control trees were compared by Mann- Whitney U-tests (Siegel 1956). Food habits were studied in the 4 largest roosts by analyzing pellets collected from beneath the roost trees during September 1988. Bones, hair and feathers obtained Table 2. Comparison between the characteristics of roost (r) and control (c) trees in each of 4 main roosts. In roost 1 , the 3 nuclei (A, B, and C) have been considered separately. Mean, standard deviation (parentheses) and significance of the differences for each variable are shown (Mann- Whitney Z7-tests). Roosts 1 A 1 B 1 C 2 3 4 R c R c R c R c R c R c N = 5 N = 5 N = 6 N = 6 N = 5 N = 5 N = 9 N = 12 N = 6 N = 8 N = 13 N = 7 1) Diameter (cm) 43.2 40.0 34.3 26. 2 a 36.0 41.6 23.1 22.2 40.2 31.0 b 45.6 29. 0 b (12.2) (9.0) (5.7) (3.3) (9.1) (12.1) (2.5) (2.5) (6-3) (5.7) (12.1) (9.6) 2) Height (m) 6.5 8.3 10.1 9.0 6.4 5.4 14.9 15.0 15.3 11.9 3 10.0 6.7 (2.2) (1.9) (1.4) (1.3) (1.1) (1.3) (0.3) (0.0) (1.8) (2.6) (2.4) (1.1) 3) Number of 0.6 1.6 a 3.2 6.3 b 1.0 3.8 a 11.3 15. 6 b 5.0 4.5 1.6 1.1 trees (0.6) (1.8) (1.5) (2.2) (0.7) (2.3) (2.2) (2.6) (2.4) (3.3) (1.0) (0.9) 4) Foliage (1-5) 5.0 1.8 b 2.7 2.7 4.8 1.4 b 2.1 2.0 2.7 1.8 2.6 2.6 (0.0) (0.8) (0.8) (0.8) (0.5) (0.6) (0.3) (0.0) (0.8) (0.5) (1.0) (1-3) 5) Open space (%) 94.0 77.0 53.3 45.8 96.0 62. 0 a 60.6 22. 9 C 72.5 71.9 73.9 87.0 (13.4) (22.8) (12.1) (31.7) (8.9) (29.7) (12.1) (18.6) (14.8) (23.0) (21.4) (15.0) a P < 0.05; b P < 0.01; c P < 0.001. Spring-Summer 1990 Egyptian Vulture Roosts 21 from pellets were classified by comparison with collections and occasionally by consulting identification keys (Faliu et al. 1980, Pinto 1980). Most of the Egyptian Vulture’s food comes from carrion which is difficult to quantify. For this reason, we decided to estimate only frequencies of appearance/pellet (number of occurrences x 100/total number of pellets) and not to calculate numeric and bio- mass frequencies. Seasonal changes in number of roosting Egyptian Vul- tures were studied in the roost where the largest number of birds were present. We conducted counts weekly from the end of February to the end of September 1988. Counts were made at the end of the day by 2-3 observers working in such a way that the whole roost could be covered si- multaneously. In other species of roosting vultures (Ca- thartidae), counts are done on birds departing from the roost in the early morning due to difficulty in conducting observations in trees with dense foliage (Sweeney and Fra- ser 1986). Egyptian Vultures, however, roost in trees with little foliage or, as often happens, in dead trees. Thus, determining numbers in the evening before darkness was relatively easy. Three age classes (juvenile, immature and adult) were distinguished by differences in plumage col- oration (see Porter et al. 1974, Cramp and Simmons 1980). Telescopes (20-90 x) were used in all observations at dis- tances ranging between 200 and 500 m. Results Description of Roosts and Tree Characteris- tics. Six Egyptian Vulture communal roosts were located. General roost characteristics are described in Table 1. Four roosts were in pine trees, 1 in European white poplar ( Populus alba), and 1 on a clay cliff. The maximum number of Egyptian Vul- tures observed in each roost was highly variable (max = 138; min = 8). Percentage of birds in im- mature plumage was relatively similar between roosts (19.6-28.3%). Griffon Vultures (Gyps fulvus) , Red Kites ( Miluus milvus). Black Kites (M. migrans ) and Common Ravens (Corvus corax) were observed roosting regularly with Egyptian Vultures. Occa- sionally, individual birds of other species were also seen roosting [i.e., Booted Eagle ( Hieraaetus pen- natus), Honey Buzzard (Perrtis apivorus). Peregrine Falcon (Falco peregrinus) and Jackdaw ( Corvus mo- nedula)]. In all roosts Egyptian Vultures perched together except in the case of roost 1 which was composed of 3 separate nuclei at an average distance of 1210 m. Egyptian Vultures roosted indiscrimi- nately in the 3 nuclei. Changes seemed to depend on weather and human disturbance (Donazar and Ceballos 1987). Differences observed among roosts with respect to tree-selection (Table 2) might simply be a result of different characteristics in a given woodlot. In roosts Table 3. Results of pellet analysis of roosting Egyptian Vultures (values represent frequency of ap- pearance per pellet). 1 Roost 2 3 4 Mammals Oryctolagus cuniculus (wild) 42.4 16.7 4.1 19.1 Unidentified rodent — 1.5 4.1 3.2 Felts catus — 1.5 6.1 — Canis familiaris 1.7 — 4.1 6.4 Meles meles — 1.5 — — Vulpes vulpes 1.7 — — — Equus caballus — — 2.0 — Sus scrofa (domestic) 33.9 47.0 8.2 20.6 Sus scrofa (wild) — 3.0 4.1 — Bos taurus 1.7 7.6 14.3 4.8 Ovis aries 20.3 50.0 73.5 22.2 Capra hircus — 1.5 — — Unidentified mammal 8.5 1.5 2.0 1.6 Birds Gallus gallus 54.2 25.8 10.2 95.2 Corvus monedula — — 2.0 — Unidentified Corvidae 1.7 4.6 — 1.6 Unidentified birds 3.4 3.0 — 6.4 Reptiles Lacerta lepida 1.7 — — — Fishes Unidentified fishes — — — 1.6 Invertebrates Coleoptera 22.0 6.1 8.2 14.3 Garbage (synthetic materials) 3.4 9.1 51.0 1.6 Plant matter 47.5 48.5 24.5 27.0 Number of pellets 59 66 49 63 IB, 2, 3 and 4, homogeneity of the trees was no- ticeable, and differences between roost and control trees were necessarily small. In these roosts, birds chose trees for roosting with a large basal diameter. Roost 2 consisted of planted pine, and vultures roost- ed in trees along the border of the forest. Vultures strongly preferred isolated dead trees wherever available (roosts 1A and 1C). Food Habits. Food of roosting Egyptian Vultures was extremely varied (Table 3). A few species were represented in most of the pellets: European Rabbit (Oryctolagus cuniculus), pig (Sus scrofa domestica ), 22 Olga Ceballos and Jose A. Donazar Figure 1 . Number of Egyptian Vultures observed in roost 1 during 1988. sheep {Ovis aries) and Domestic Fowl (Gallus gallus) . Dominant prey remains in pellets varied from one roost to another and seemed a simple consequence of availability of food. Thus, in roosts 1 and 4, food was based on fowl raised on nearby farms. In roost 1, wild rabbits, which were abundant in the area, also entered in the diet. In roost 2 a pig slaughter house provided most of the food, and in roost 3, vultures foraged in a garbage dump containing re- mains of slaughtered sheep. A high frequency of plant matter in pellets cannot be accidental, given that plant material dominated in most pellets in which it appeared. Generally, plant remains consisted of stems and seeds of wild and cultivated grains as well as fruit seeds (cherry, melon and watermelon). The largest quantities of plant material appeared to be associated with hair and wool, suggesting that vul- tures ingest plant matter to aid in pellet formation. Roost Seasonal Dynamics. Results of weekly counts in roost 1 are summarized in Figure 1. Vul- tures first arrived the last week of February. Num- bers increased progressively, reaching a maximum in July- August, after which numbers dropped until the end of September when the last birds left. Al- though overall tendencies were constant, there were strong weekly fluctuations. A total of 1757 vultures were observed during 1988; 1275 (72.6%) adults, 468 (26.6%) immatures and 14 (0.8%) juveniles. Throughout the study period there were adult Egyp- tian Vultures in the roost. Birds in immature plum- VOL. 24, Nos. 1-2 MONTHS Figure 2. Monthly changes (number of vultures) in roost 1 during 1988. Changes are differences be- tween monthly mean numbers of birds. age, however, were not recruited until April-May. Between May and September immatures constituted a large part of the total number of birds (monthly average = 38.4%). Immigration rate of adults and immature birds differed noticeably throughout the study period (Fig. 2). Adults increase sharply from March- April and June- July, while immatures in- creased most sharply in the first 2 months of their appearance in the roost (May- June). Consequently, the ratio of adults to immatures varied substantially during the year (Fig. 3). With the arrival of the first immatures, the number of adults per immature dropped noticeably, gradually recovering later with the arrival of new adults. Juvenile Egyptian Vul- tures (hatched in 1988) frequented the roost in the last weeks of August and the first weeks of September (Fig. 1). Juveniles and immatures left the roost 2 wk before adults. Discussion Roost and Tree Characteristics. As in other parts of the Palearctic (see Cramp and Simmons 1980) Figure 3. Ratio of adults/immatures in roost 1 during 1988. Spring-Summer 1990 Egyptian Vulture Roosts 23 the Egyptian Vulture preferentially chose trees for roosting in our study area. The choice of pines for roosting may only be a consequence of abundance in the study area and of the fact that pines in Spain reach taller heights than broad-leafed trees. Asso- ciated avian species observed in roosts were mainly carrion-eaters, which supports the opinion that mixed roosts may have a function related to transfer of foraging information (Ward and Zahavi 1973, but see Bayer 1982). However, species did not scavenge frequently together in the study area and usually occupied separate zones in the roosts. Observed tendencies in tree-selection suggest that trees are chosen on the basis of 2 fundamental factors: 1) size of the tree (basal diameter) which is necessary for supporting several birds at a time; and 2) ability to enter and leave without the foliage of the roost tree and neighboring trees getting in the way (ten- dency to choose dead, isolated trees with an open crown). Roosting New World vultures and large eagles have also been reported to show a preference for large trees with easy access (Wright et al. 1986, Isaacs and Anthony 1987). Wright et al. (1986), however, indicated that wintering Black ( Coragyps atratus) and Turkey Vultures (Cathartes aura) choose trees with abundant foliage (conifers) which provide a favorable microclimate. This is not the case with the Egyptian Vulture, which tends to choose trees without foliage probably because its roosts are in warm areas and form during warm seasons. Food Habits. Roosting Egyptian Vulture food is, in general, similar to that of breeding pairs in the study area (see Donazar and Ceballos 1988) and reflects the great foraging eclecticism of the species (Bergier and Cheylan 1980, Cramp and Simmons 1980). In each roost, food habits seem to reflect ac- curately the availability of different kinds of carrion in feeding grounds nearest to roosts. This was also indicated by a radiotracking study of 3 Egyptian Vultures (2 adults; 1 immature) frequenting roosts 1 and 3 (Donazar and Ceballos 1987). The ap- pearance of plant matter in pellets is also known in other Old World species, such as Griffon Vultures which ingest large portions of carrion without hair or feathers (pers. obs.) and has also been reported in Cathartidae (Paterson 1984, Inigo 1987). The appearance of fruit seeds in pellets also suggests that vultures may exploit some resources that can be eas- ily found in garbage dumps. Frequent consumption of tropical fruits has been reported for Black Vul- tures in Mexico (Inigo 1987). Finally, the ingestion of plastic and synthetic materials might be explained for one of a variety of reasons: mistaken for bone fragments (Mundy 1982), as an aid to pellet for- mation, or ingested accidentally when vultures eat food placed inside plastic bags (Inigo 1987). Roost Seasonal Dynamics. Progressive increase in the total number of Egyptian Vultures in the study area may only be a consequence of greater avail- ability of food during summer. In July, August and September the items most frequently consumed (hen, pig and wild rabbit) undergo a higher death rate than in winter and spring. Hen and pig mortality is directly related to outdoor temperature (I.T.G. Porcino, pers. comm.), and rabbit mortality increases in the last part of the summer owing to myxomatosis (pers. obs.). In consequence, the roost might be fre- quented more often at these times by breeding and non-breeding birds searching for food, such as occurs in other large roosting raptors (Isaacs and Anthony 1987). We believe, however, that this cannot be the only valid explanation, as the availability of food in our study area was extraordinarily high in all sea- sons. In the village nearest roost 1, there were 26 000 pigs and 51 000 hens which were expected to provide a monthly average of 15 and 153 carcasses, respec- tively. On the other hand, immigration rate is high during the months May- June before the expected high mortality of livestock and wild rabbit takes place. In our opinion, the observed dynamics of the larg- est roost could be in response to 2 factors: 1) changes in relative frequencies in the population of non- breeding birds (adults and immatures); and 2) changes in the breeding status of adults. Spring mi- gration of adult Egyptian Vultures through Gi- braltar continues after the start of the reproductive season in Spain (see Cramp and Simmons 1980). For this reason, a progressive increase of adults in the roost in early spring might result from numbers of non-breeding birds, perhaps adults in their first plumage, migrating late. Moreover, the increase in immatures observed in the roost in late spring may also correspond to late migrants since in May and June a great number of immatures can be seen cross- ing from Africa to Spain (Bergier 1987). On the other hand, peaks observed in the rate of increase of adult vultures coincide with critical periods in the breeding cycle: egg-laying (March-April) and the first month of chick development (June- July). Roosts might receive a number of adults whose breeding attempt had failed. However, this implies that roosts 24 Olga Ceballos and Jose A. Donazar Vol. 24, Nos. 1-2 would receive birds from a wide area since the num- ber of roosting adults makes up about 25% of the breeding population of the study area, and frequency of breeding failure in the area is relatively low (Do- nazar and Ceballos 1988). Further, high numbers of immatures observed in the studied roosts supports our conclusion. The Egyptian Vulture, in common with other large raptors (Brown and Amadon 1968, Hiraldo et al. 1979, Piper et al. 1981) may undergo a high pre-adult mortality, which leads us to con- clude that immatures observed in our roosts come from a wide area. This conclusion is reinforced by the very scarce reports on observations of immature birds out of roosts in Spain (J.L. Perea, pers. comm.). It has frequently been claimed that immatures do not return to Europe until acquiring adult plumage (Stresemann, Ridell in Cramp and Simmons 1980, Geroudet 1965). Results of a radiotelemetry study of 3 adult Egyp- tian Vultures in the area of roosts 1, 3 and 5 suggest that roosts receive both breeding and non-breeding adults (Donazar and Ceballos 1987, Ceballos and Donazar 1989). Two marked birds were non-breed- ing birds that depended totally on the roost and neighboring feeding sites. The other radio-tagged adult was a breeding female which only frequented the roost at night. In New World Vulture roosts, the presence of breeding adults from adjacent ter- ritories and of non-breeding adults has been reported (Rabenold 1986, 1987). Finally, the appearance during August and September of juveniles recently fledged could be interpreted as the recruitment of family groups as happens in Black Vultures (Ra- benold 1986). We did not, however, see any behavior in juveniles (begging, feedings by adults) which would indicate dependence. More probably, roosts are used as rest stops by juveniles during migration. In fact, a young bird we marked rested 1 night in roost 6 after starting migration. The bird’s natal territory was 6 km from the roost, and the bird migrated without its parents. Acknowledgments We are grateful to Alejandro Urmeneta and Ignacio Garcia Bello for field assistance; to Fernando Hiraldo who provided guidance throughout this study and revision of the manuscript; to Sanford R. Wilbur, David C. Houston, and Alistair Robertson who provided constructive criti- cisms of the manuscript; and to Catherine Miller who made the English translation. The study was partially financed by the Instituto Nacional para la Conservation de la Naturaleza (Section de Recursos Naturales Renov- ables), and a FPI-grant from the C.S.I.C. to one author (J.A.D.), Project DGJCYT, PB87-0405. Literature Cited Bayer, R.D. 1982. How important are bird colonies as information centers. Auk 99:31-40. Bergier, P. 1987. Les rapaces diurnes du Maroc. An- nales du C.E.E.P. no. 3. and G. Cheylan. 1980. Statut, succes de re- production et alimentation du vautour percnoptere Neophron percnopterus en France mediterraneenne. Alauda 48:75-97. Brown, L. and D. Amadon. 1968. Eagles, Hawks and Falcons of the world. Country Life Books, London. Ceballos, O. and J.A. DonAzar. 1989. Actividad, uso del espacio y cuidado parental en una pareja de Ali- moches ( Neophron percnopterus ) durante el periodo de dependencia de los polios. Ecologia 2:34-45. Congost, J. and J. Muntaner. 1974. Presencia otonal e invernal y concentracion de Neophron percnopterus en la isla de Menorca. Misc. Zool. 3:1-11. Cramp, S. and K.E.L. Simmons (Eds.). 1980. The birds of the western Palearctic. Vol. 2. Oxford University Press, Oxford. Donazar, J.A. and O. Ceballos. 1987. Parametros reproductores y uso del espacio en el Alimoche (Neo- phron percnopterus). Unpubl. report. I.C.O.N.A., Sec- tion de recursos naturales renovables, Madrid. AND . 1988. Alimentation y tasas re- productoras del Alimoche ( Neophron percnopterus ) en Navarra. Ardeola 35:3-13. Faliu, L., Y. Lignereux and J. Barrat. 1980. Iden- tification des poils des mammiferes pyreneens. Donana , Acta Vert. 7:125-212. Geroudet, P. 1965. Les rapaces diurnes et nocturnes d’Europe. Delachaux et Niestle, Neuchatel. Hiraldo, F., M. Delibes and J. Calderon. 1979. El Quebrantahuesos Gypaetus barbatus (L.). I.C.O.N.A. Monografias 22, Madrid. IftlGO, E.E. 1987. Feeding habits and ingestion of syn- thetic products in a Black Vulture population from Chiapas, New Mexico. Acta Zool. Mex. (ns) 22:1-11. Isaacs, F.B. and R.G. Anthony. 1987. Abundance, foraging, and roosting of Bald Eagles wintering in the Harney Basin, Oregon. Northw. Sci. 61:114-121. Mundy, P.J. 1982. Comparative biology of southern African vultures. Vulture Study Group, Johannesburg. Paterson, R.L., Jr. 1984. High incidence of plant ma- terial and small mammals in the autumn diet of Turkey Vulture in Virginia. Wilson Bull. 96:467-469. Pinto, M.V. 1980. Estudo morfologico dos pelos dos mamiferos portugueses. Chaves para a sua determi- nagao. Actas I reunion Iberoamer. Zool. Vert.: 629-680. Piper, S.E., P.J. Mundy and J.A. Ledger. 1981. Es- timates of survival in the Cape Vulture Gyps coproth- eres. J. Anim. Ecol. 50:815-825. Spring-Summer 1990 Egyptian Vulture Roosts 25 Porter, R.F., I. Willis, S. Christensen and B.P. Niel- sen. 1974. Flight identification of European raptors. T.& A.D. Poyser, Calton, England. Rabenold, P. P. 1986. Roost attendance and aggression in Black Vultures. Auk 104:647-653. . 1987. Recruitment for food in Black Vultures: evidence for following from communal roosts. Anim. Behav. 35:1775-1785. Siegel, S. 1 956. Non-parametric statistics for behavioral sciences. McGraw-Hill Book Company, New York. Sweeney, T.M. and J.D. Fraser. 1986. Vulture roost dynamics and monitoring techniques in southwest Vir- ginia. Wildl. Soc. Bull. 14:49-54. Ward, P. and A. Zahavi. 1973. The importance of certain assemblages of birds as “information-centres” for food-finding. Ibis 115:517-534. Wright, A.L., R.H. Yahner and G.L. Storm. 1986. Roost-tree characteristics and abundance of wintering vultures at a communal roost in south central Penn- sylvania. Raptor Res. 20:102-107. Received 20 March 1989; accepted 15 December 1989 J Raptor Res. 24(l-2):26-27 © 1990 The Raptor Research Foundation, Inc. Short Communications Bald Eagle Attacks Osprey Nestling Stephen P. Flemming Department of Biology, Queen’s University , Kingston, Ontario, Canada K7L 3N6 Robert P. Bancroft Department of Lands and Forests, P.O. Box 698, Halifax, Nova Scotia, Canada B3f 2T9 The incidence of kleptoparasitic and agonistic interac- tions between Bald Eagles {Haliaeetus leucocephalus) and Ospreys ( Pandion haliaetus) are well documented (Bent 1937, Ogden 1975, Gerrard et al. 1976, Prevost 1979). However, to our knowledge, there has been no recorded observation of a physical attack by a Bald Eagle on an Osprey. Here, we describe such an observation, and discuss possible reasons for its occurrence. The observations were made in northeastern Nova Sco- tia while conducting research on the social behavior of Ospreys. On 16 August 1985, a 20 cm Winter Flounder ( Pseudopleuronectes americanus) was brought to a single unfledged nestling by its female parent Osprey between 1833 H and 1835 H. At 1835 H an adult Bald Eagle flew directly to the nest from the same direction as the Osprey, landing on the nestling, aged 55 days (mean nestling period was 55.3 days, N = 10). The Bald Eagle maintained its grip for 25 sec. During this time the chick moved across the nest and finally fell after much struggle and wing flapping. It was subsequently lost from view at our blind 300 m away. The eagle then grabbed the flounder with its talons and flew to a nearby tree, where the female Osprey began diving at it. After approximately 11 min the eagle departed, pursued by the Osprey. The nestling was not located despite a search and a further week of nest observations. Whether it survived the attack or died near the nest is unknown. It seems likely that the eagle was originally intent on stealing the adult Osprey’s flounder, a common occurrence on foraging sites and near nests in our study area. How- ever, when the eagle’s attention was diverted to the nest by the fish delivery, it was suddenly confronted with a nestling as well as the flounder. The eagle may have in- terpreted this in at least two ways. The nestling could have been perceived as an obstruction to the flounder and was subsequently attacked, or the eagle may have chosen to attack the nestling because it represented a more profitable prey item than the flounder. If the eagle was simply trying to take the flounder from the nestling, this behavior differs little from typical klep- toparasitism, except for the physical contact. However, given the aggressive nature of the attack, it seems at least equally likely that the eagle acted opportunistically to exploit a larger food reward. If so, this observation could represent the first recorded switch from kleptoparasitism to predation. Brockmann and Barnard (1979) stated that an important interspecific association that may lead to kleptoparasitism is the one based on predation. But, they also noted that kleptoparasitism leading to predation can also be envisioned, yet no documented case exists. The unusual circumstances surrounding this observa- tion could explain why it may have been the exception to the pattern identified by Brockmann and Barnard (1979). Several constraints probably limit the viability of switching from kleptoparasitism to predation. Among the most ob- vious are 1) the low probability of success due to inex- perience and possible anatomical constraints, and 2) the loss of a food item every time a predation attempt is made, since it would be dropped in the pursuit. In this case, the host was a nestling that was unprotected and inexperi- enced, something the eagle may have surmised. Moreover, the eagle was almost certain to obtain the flounder re- gardless of the outcome because it was readily available on the nest. Under these conditions, the eagle may have viewed a predation attempt as viable. Resumen. — Mientras observabamos, desde un escondite, Aguilas Pescadoras (. Pandion haliaetus ) en un estudio del comportamiento social de esta especie, notamos que una Aguila cabeciblanca ( Haliaeetus leucocephalus) atacaba en el nido a un polluelo de Aguila Pescadora. El ataque se produjo entre 1 y 2 minutos despues que el polluelo habia recibido un pescado de su progenitor. En lugar de apro- priarse del pescado el ataque fue contra el polluelo. Pen- samos que la original intention del atacante era la de robar el pescado. El Aguila Cabeciblanca puede haber atacado al polluelo, ya casi en estado adulto, por una de las siguin- tas razones: 1) Porque el polluelo Pandion haliateus representaba una amenaza al atacante en su intento de robar el pescado, o 2) Porque el Aguila Cabeciblanca consideraba al polluelo mejor presa que el pescado. [Traduction de Eudoxio Paredes-Ruiz] Acknowledgments We thank our field assistant, E. Floyd, for her detailed note taking, and the Nova Scotia Department of Lands 26 Spring-Summer 1990 Short Communications 27 and Forests, and the Canadian Electrical Association for financial support. Literature Cited Bent, A. C. 1937. Life histories of North American birds of prey, Part 1. U.S. Natl. Mus. Bull. 167. Brockmann, H.J. and C.J. Barnard. 1979. Klepto- parasitism in birds. Anim. Behav. 27:487-514. Gerrard, J.M., D.W.A. Whitefield and W.J. Maher. 1976. Osprey-Bald Eagle relationships tn Saskatchewan. Blue Jay 34:240-246. Ogden, J.C. 1975. Effects of Bald Eagle territoriality on nesting Ospreys. Wilson Bull. 87:496-505. PrEvost, Y. 1979. Osprey-Bald Eagle interactions at a common foraging site. Auk 96:413-414. Received 1 March 1990; accepted 3 May 1990 /. Raptor Res. 24(l-2):27-28 © 1990 The Raptor Research Foundation, Inc. Orientation of American Kestrel Nest Cavities: Revisited Thomas G. Balgooyen Department of Biological Sciences , The Avian Biology Laboratory, San Jose State University, San Jose, CA 95192 Recently, Raphael (1985) reviewed Balgooyen’s (1976) orientation data of American Kestrel ( Falco sparvenus) nest cavities and trees at Sagehen Creek, 1 800 m elevation, Sierra and Nevada Counties, California. Balgooyen sug- gested that kestrels select nest cavities with east-facing exposures to gain a thermal advantage. Raphael confirmed a preference for east-facing cavities when alternatives were available. Assuming a thermal advantage, woodpeckers and kes- trels could prefer, or be independent of certain environ- mental temperatures, thus possibly forcing species to com- pete for cavities. Clearly, available cavities are neither evenly spaced nor random in orientation (Raphael 1985) suggesting, among other possibilities, that these species are not independent of the thermal environment particularly in “cold” environments. At Sagehen Creek, inclement weather during the breeding season enters from the South (SE, S, SW). Predictably, both kestrels (19.0%, N = 11/ 58) and woodpeckers (21.9%, N = 23/105) avoid this “cold” direction. In addition, both kestrels (25.8%, N = 15/58) and woodpeckers (28.6%, N = 30/105) nested at relatively low frequency in the “hot” directions of the West (SW, W, NW) (Balgooyen 1976, Raphael 1985). Woodpecker cavities were oriented to the North (N = 105, mean azimuth = 14°), yet kestrels, which depend on woodpeckers, (60.53%, N = 35/58, mean azimuth = 59°) and woodpeckers (only 40.0%, N = 42/105) nested in cavities facing easterly. The opposite occurred to the North with nesting frequencies of 41.3% (N = 24/58) for kestrels and 57.1% (N = 60/105) for woodpeckers. It is possible that woodpeckers and kestrels possess different thermal preferences during nesting, kestrels seemingly preferring warmer places than woodpeckers. An apparent difference in thermal preference might reflect different racial his- tories of woodpeckers from northern areas and kestrels from grassland-savanna systems. There is, however, op- portunity for direct competition for a given cavity. This has been directly but infrequently observed at Sagehen Creek (Balgooyen 1976). In 1983, 29 breeding pairs of American Kestrels were located in western Venezuela. In the States of Zulia and Tachira, 23 of the 29 pairs nested within the southwestern base of the Andes Mountains south of Lake Maracaibo (8°2'N Lat., 72°16'W Long). Four pairs nested in the basin of the Rio Chama, Merida, 1 pair resided in Barquisimeto, Lara, and the last pair nested near Barines, Barines. A wet nonbreeding and dry breeding season characterize the Table 1, Nest orientation of American Kestrel nests in western Venezuela, S.A. Direction Midpoint Azimuth of Group (°) Nest Entrance Orienta- tion (N = 29) % North 0 7 24.1 Northeast 45 2 6.9 East 90 2 6.9 Southeast 135 2 6.9 South 180 7 24.1 Southwest 225 3 10.3 West 270 2 6.9 Northwest 315 4 13.8 28 Short Communications Vol. 24, Nos. 1-2 area (Balgooyen 1989). During the breeding season (De- cember to April), high humidity, high temperatures, and moderate breezes along a NS axis persist in the general area of study. Lands have been cleared for cattle produc- tion with intensive management by tilling and planting of non-native grasses. Palms held 14 of 29 (48.3%), araguaney ( Tabebuia chry- santha) and ceiba (Ceiba pentandra) trees possessed exca- vated cavities for the remainder. Nesting at the base of palm fronds provided an opportunity for kestrels nesting in all compass orientations. A working hypothesis that kestrels avoid heat by nesting into the wind and away from direct sunlight needs testing. The G-Test with a William’s correction (Sokal and Rohlf 1981) statistically compares the frequencies of nest orientation (Table 1) in the compass corridors of N-S, E-W (90°), NE-SW (45°), and NW-S (120°). Depending upon local conditions, the windy cor- ridor consisted of nests oriented N-S (N = 13), NW (N = 1), and NE (N = 1) or 15 of 29 nests faced into the prevailing winds. The “sun” corridor of E-W included 4 of the total nests. In two cases of nest destruction, pairs selected new sites similar to their former cavities with directions avoiding heat. Analysis by the G-Test (G adj = 9.75, x 2 (oo 5 ) = 7.82) indicates that kestrel nest sites are not uniformly distributed (P — 0.025). The windy corridor seems favored by tropical kestrels. One palm held a wasp’s nest oriented to the N, a yellow- headed parrot ( Amazona orchocephala) nest oriented to the NW, a tropical screech owl ( Otus asio choliba ) nest oriented to the SE, and a kestrel pair was the last to breed which may have limited the nest orientation to the vacant “hot” position in the East. Three eggs were laid and hatched, one young died, and two individuals fledged. While further study is in order, kestrels may select a nest with an orientation in relation to the thermal demands of the environment in both North and South America. My thanks to Martin G. Raphael for comments and to Bill Bros for statistical analysis on this communication. Resumen. — Mientras que los gavilanes primitivo ( Falco sparverius ) de la Sierra Nevada en California prefieren cavidades para sus nidos con orientation hacia el este y oeste, gavilanes de los llanos de Venezuela ocupan nidos que cavean los vientos (de norte a sur). Los gavilanes pueden seleccionar cavidades para sus nidos en relacion a las caracteristicas termales del ambiente. Literature Cited Balgooyen, T.G. 1976. Behavior and ecology of the American kestrel ( Falco sparverius ) in the Sierra Ne- vada of California. Univ. Calij. Publ. Zool. 103:1-87. . 1989. Natural history of the American kestrel in Venezuela. J. Raptor Res. 23:85-93. Raphael, M.G. 1985. Orientation of American kestrel nest cavities and nest trees. Condor 87:437-438. Sokal, R.R. and F.J. Rohlf. 1981. Biometry. W.H Freeman, San Francisco, CA. J Raptor Res. 24(l-2):28-29 © 1990 The Raptor Research Foundation, Inc. Cannibalism by Black Kite {Milvus migrans ) A. M. Jones 1 Museo Nacional de Ciencias Naturales, J. Gutierrez Abascal 2, 28006 Madrid, Spain M. Manez Equipo de Conservacion , Parque Nacional de Donana, Centro Administrativo, “El Acebuche,” 21760 Matalascanas, Huelva, Spain Acts of cannibalism by birds are difficult to witness because of their brevity and thus may be underrecorded at nests. Among raptors, cannibalism has been considered rare and incidental to brood reduction (Mock 1984) but may be selected for if food is in short supply or unpre- dictable (see Alexander 1974). 1 Present address: R.S.P.B., Highlands Office, Munlochy, Ross & Cromarty, 1V8 8ND, Scotland. We report on an adult Black Kite ( Milvus migrans) eating a Black Kite nestling, indirect evidence of canni- balism by Black Kite in the same area and discuss a pos- sible influence of food shortage. Black Kite nestlings have previously been found partly eaten by siblings in the Bi- ological Reserve of Donana on 4 occasions (Delibes 1975) Observations of nesting Black Kites were made in the Pinar del Faro and elsewhere in Donana National Park, Spain (36°48'N, 6°22'W). On 18 June 1987 at 1130 H Spring-Summer 1990 Short Communications 29 GMT we flushed a feeding adult kite from a nest located in a stone pine (Pinus pinea). A freshly dead nestling was retrieved from the nest which contained no other food item. The dead nestling’s left femur was picked clean of flesh and the head, viscera and part of the left side of the body were missing. The carcass weighed 141 g and the crop was empty. Using wing feather growth, we estimated the nestling was 12 d old (see Hiraldo et al. in press). The adult, which did not attempt to carry the carcass, showed attachment to the site and may have been a parent at this nest, which was unoccupied in 1988. Two other nests 200 m from one another contained nestlings and prey remains on our visit on 18 June 1987. Ages of the young were estimated from wing feather growth (see Hiraldo et al. op cit.). Young at the first nest were approximately 25 and 29 d old and 22 and 25 d old at the second. On 27 June 1988 a color band from the oldest nestling of the second nest was found beneath the first nest in good condition, unopened. The first nest contained 1 nestling close to fledging age, and the second nest was unoccupied. Prey remains accumulate beneath kite nests and we suspect the band arrived beneath the first nest after its owner had been taken from the nest as a nestling and eaten there in 1987. We consider an alternative possibility, that the dead nestling was carried as, or attached to, an item of robbed nest material from which the band later fell, unlikely. Food shortage could drive parents to eat their own young or to leave nestlings unguarded, thereby increasing the probability of cannibalism or nest predation. In Pinar del Faro in 1987, where we observed cannibalism, there was a mean of 1.94 nestlings/successful nest (17 successful, 2 unsuccessful), very similar to the mean of 1.95 nestlings for successful nests elsewhere in Donana in 1987 (92 suc- cessful, 8 unsuccessful) where cannibalism may have been overlooked; but below the value for the adjacent area of Marismillas (2.22 nestlings/successful nest, 18 successful, 2 unsuccessful; brood sizes not significantly different, x 2 = 1.6, df = 2, P > 0.05). We found no significant differ- ences between brood sizes in Pinar del Faro in 1987 and later years (for 15 successful nests in 1988, x 2 = 1-96, df = 1, P > 0.05, mean =1.4 nestlings/successful nest; for 11 successful and 1 unsuccessful nest in 1989, x 2 = 0.19, df = 1, P > 0.05, mean = 1.81 nestlings/successful nest). Information on the circumstances and incidence of can- nibalism of nestlings by adult raptors is scant but suggests the phenomenon is common where nestlings are weak or hunting is difficult. Thus, a female European Sparrow- hawk ( Accipiter nisus ) killed and then probably ate the youngest and most underweight of its brood (Newton 1978) and cannibalism in this species can be associated with wet weather (Moss 1979). The disappearance of Peregrine Falcon (Falco peregrmus) nestlings and recovery of nestling remains at plucking posts close to nests at inland sites in southwest Scotland, indicating parental cannibalism, oc- curred in 1976, when it was exceptionally wet during the main hatch period (R. Mearns, pers. comm.). We cannot rule out difficult hunting conditions as a factor in the cannibalism we observed but such behaviour may be less exceptional in a versatile and opportunistic feeder like the Black Kite than the absence of earlier records (see Cramp and Simmons 1979) indicates. Resumen. — Hemos observado un milano negro ( Milvus migrans) alimentando en el nido a un polluelo de 12 dias de nacido. El ave adulta se comportaba como si fuera el dueno del nido. Un polluelo desaparecio de cada uno de dos nidos adicionales, a causa de lo que, por las circun- stancias presentes, se sugirio fuera canibalismo. Se supuso que la carencia de alimentos hubiera sido la causa para que los adultos comieran sus polluelos, o abandonaran el nido por largos periodos de tiempo, causando asi la muerte de los pequenos. [Traduccion de Eudoxio Paredes-Ruiz] Acknowledgments Observations were made while AMJ, who acknowl- edges CSIC-CICYT support, was working from the Mu- seo Nacional de Ciencias Naturales, Madrid, with a grant from the Ministerio de Educacion y Ciencias and super- vision from Drs. F. Hiraldo and J. C. Alonso. We are grateful to Mick Marquiss, M. Espinar Anillo of Pinar del Faro, Richard Mearns for unpublished peregrine ob- servations, Javier Vinuela for 43 kite nest records and to Christopher H. Stinson and Allan M. Strong for helpful comments. Literature Cited Alexander, R.D. 1974. The evolution of social be- havior. Ann. Rev. Ecol. and System. 5:325-383. Cramp, S. and K.E.L. Simmons. (Eds.). 1979. Pages 27-36. In The birds of the western Palearctic, Vol. 2. Oxford. Delibes, M. 1975. Feeding ecology of the Black Kite in Donana South Spain (in Spanish with English sum- mary). Ardeola 21 (special volume): 183-207. Hiraldo, F., J.P. Veiga and M. MaNez. In press. Growth of nestling Black Kites Milvus migrans: effects of hatching order, weather, time and season. J. Zool., London. Mock, D.W. 1984. Infanticide, siblicide and avian nest- ling mortality. Pages 3-30 in G. Hausfater and S. Blaffer Hrdy, Eds. Infanticide: Comparative and evolutionary perspectives. Aldine, New York. Moss, D. 1979. Growth of nestling Sparrowhawks ( Ac- cipiter nisus). J. Zool., London 187:297-314. Newton, I. 1978. Feeding and development of Spar- rowhawk Accipiter nisus nestlings. /. Zool., London 184: 465-487. Received 20 April 1989, accepted 15 December 1989 /. Raptor Res. 24(l-2):30-37 © 1990 The Raptor Research Foundation, Inc. News and Reviews Flight strategies of migrating hawks by Paul Kerlinger. University of Chicago Press, Chicago, 1989. xv + 375 pp. ISBN 0-226-43166-5. Cloth, $60.00 U.S. ISBN 0-226-43167-3. Paper, $19.95 U.S. Much of the literature on avian migration is based on counts of birds moving past various strategic locations where they are concentrated over relatively small areas by local geography. The focus of this monograph takes the reader away from such an approach to migratory raptors and looks instead at the mechanics of migration, emphasizing the quantification of numerous aspects of migratory flight in Falconiformes and the development of testable hypotheses Kerlinger views his contribution as the second of a three-step process toward a better understanding of migration. The initial step, which provided the foundation for Kerlinger’s work, was Heintzelman’s (1975. Autumn hawk flights, the migrations in eastern North America. New Brunswick, New Jersey; Rutgers University Press) summary of the information available up to the mid 1970s. As the second major step, Kerlinger’s monograph establishes a much stronger empirical basis and develops testable hypotheses for the third phase of the process which will integrate this information into a comprehensive theory on migratory flight strategies and provide insight into how natural selection affects the development and evolution of migratory behavior. Kerlinger begins the monograph with four chapters introducing general concepts of hawk migration and its study In Chapter 1, migration is defined in spatial and temporal terms and all Falconiformes are placed in one of four categories: nonmigratory, irruptive, partial migrants, and complete migrants. The ecology and geography of migration are briefly reviewed and hypotheses regarding the development of differential migration are presented. Chapter 2 calls into question many of the results from studies conducted at migration (trapping) stations and the interpretation which has been given to these data, particularly those studies which attempt to explain the behavior of birds based solely on counts of raptors moving past these stations. There is a detailed description of the functions and activities of hawk migration stations, and Kerlinger does an excellent job of reviewing the different methods used to study migrating hawks, as well as analyzing their validity and reliability. Beginning in Chapter 3, and throughout the remainder of the monograph, Kerlinger uses the analogy of human flight in small aircraft to address questions of avian flight strategies. It proves to be a useful analogy which greatly enhances the reader’s understanding of the constraints placed on birds through comparison with powered and unpowered flight by man. Kerlinger proposes that migratory flights must be based on a plan or strategy which molds the behavioral, morphological, and physiological adaptations of migrants through natural selection. To facilitate the examination of this process, Kerlinger produces a flow diagram dividing migratory behavior into the components of morphology, physiology, and behavior, which act in concert with geography, weather, and topography to form a migratory strategy On this basis, he develops the hypotheses to be tested reflecting the decision-making process of migration. In the final chapter of this introductory section Kerlinger gives a detailed description of the structure of the atmosphere as it relates to soaring flight. The focus of this chapter is the extensive variability of horizontal and vertical wind conditions and the effect that this has on the flight behavior of migrants. Chapter 5 provides an overview of present theory on flight mechanics. Types of flight utilized, flight morphology (and its components of wing span, mass, wing area, and tail area), flight energetics, gliding aerodynamics, and ecomorphology are examined. The remainder of the monograph examines these theories based on the literature with a heavy emphasis on the work carried out by Kerlinger and various associates using direct observations and radar techniques over a period of about 10 years. In Chapter 6, the characteristics of raptors which allow them to take full advantage of even the weakest updrafts are discussed, particularly in relation to flight morphology, aerodynamic performance, and the ability to take advantage of thermals through behavioral modifications of the wing span, wing area, tail area, and wing tip configuration. A weakness of this section, noted by Kerlinger, is the lack of empirical data to test these theories. Data are available for only 8 species of raptors; therefore, Kerlinger also includes data for nonraptors as well as insects, bats, motorized sailplanes, and hang gliders to assess the capabilities for gliding and soaring by a wide range of sizes and shapes. In studying the role of navigation during migration, most theories on hawk movements suggest that individuals are subject to wind drift and unable to compensate for windy conditions during flight. The large numbers of birds seen on migration over count stations in eastern North America during westerly winds has been suggested to strongly favor such hypotheses. Kerlinger disagrees with the wind drift hypothesis. He presents a number of alternatives which focus on the use of flight direction in relation to wind direction, during both soaring and gliding bouts, to examine the 30 Spring-Summer 1990 News and Reviews 31 orientation abilities of migrating hawks. As an alternative, he suggests that most migratory paths are in fact curved lines, ellipses, or loop migrations with partial drift due to prevailing winds and the resulting overcompensation. The altitude of migrating hawks was poorly known prior to the use of radar technology and sailplane studies Chapter 8 presents information on the close correlation between the development of thermals through the day and the increase in migratory altitude from early morning to midday and early afternoon when the convective layer has developed. Because most smaller hawks are difficult to see above 400 m even with binoculars, and many appear to migrate at 500 m and above, Kerlinger suggests that noonday lulls and other such daily rhythms in migratory counts are likely biases and not good indicators of the number of hawks actually passing any specific point. In Chapter 9, Kerlinger examines the flocking behavior of migrating hawks. He presents several hypotheses which may explain the advantages of flocking and examines the flocking tendencies among migratory species. Kerlinger also addresses the water crossing behavior of hawks during migration. He examines this behavior in relation to the ecomorphology of the species involved, relating the tendency to make longer crossings to species with long narrow wings (high aspect ratio) which lead to faster, powered flight, along with consideration of wind and visibility conditions. The selection of flight speed in relation to maximizing the distance travelled is discussed in Chapter 1 1 . Kerlinger addresses the hypothesis that migrating hawks adjust their flight speeds to maximize the distance travelled by measuring flight speeds of several species under different wind and lift conditions. In Chapter 12, Kerlinger models the daily flight distances of migrating raptors under conditions of flapping flight, ridge-gliding, and thermal-gliding, with wind direction and speed simulated to take into account trailing, opposing and lateral wind conditions. Little information is available from free-living birds on daily migration distances. The models presented here will be useful in testing hypotheses regarding flight strategies through the use of aircraft, radar, and telemetry to examine these hypotheses. The final chapter summarizes the ongoing themes which permeate the monograph, the diversity and variability of flight behavior of migrating hawks within and among species. Kerlinger argues strongly that this variability should in fact be considered from the opposite viewpoint, that of behavioral plasticity which enables migrating birds to adjust to the continued variation in the media through which they are moving. Additionally, and perhaps more importantly, Kerlinger poses a series of questions for future work which have arisen from the current level of knowledge regarding behavior, physiology, morphology, and ecology. Some of the problems he raises are already beginning to be addressed, but many of the areas outlined will require long and expensive work with radiotelemetry, monitoring the movements and physiology of birds as they migrate between wintering and breeding grounds. Although Kerlinger identifies his audience as both the scientific community and the general public, those of the latter group may have some trouble with certain technical aspects of the monograph. The use of statistical analyses and mathematical modelling may leave even the most ardent of nonscientific readers somewhat at a loss as to the meaning of the material covered in some chapters. However, this monograph is generally well organized throughout. It begins with a series of chapters which provide a basic overview of the subject and help the reader to assess the information to follow in the second section where theory and empirical data are presented. As well, Kerlinger does a creditable job of putting much of the material into perspective during his discussion of each chapter; within each chapter he also has provided a very useful section of summary and conclusions. Provided those readers less familiar with the analytical techniques used are willing to make their way through the initial theoretical development of many chapters, they will find some very informative and stimulating discussion of the strategies involved in avian migration. The level of knowledge concerning migratory behavior has risen substantially in the last decade and general principles are now beginning to be identified. Kerlinger has done a good job of bringing the reader up-to-date on the theoretical basis for studying migratory behavior in hawks. Writing a monograph which is, at the same time, readable to an interested member of the general public and useful as a reference to scientists in the field, is a difficult task. While some parts of the text may be difficult for the amateur ornithologist, Kerlinger has succeeded in providing what should be a most useful and thought- provoking monograph for all concerned with the study of migratory behavior. — Ian G. Warkentin 32 News and Reviews Raptor Research Foundation, Inc. Life Members The Hamerstroms Frances and Frederick Hamerstrom are affectionately known to most Foundation members as Fran and Hammi (the “a” is pronounced with a Boston accent). The Ham- erstroms’ infectious fascination for raptors and their con- vincing call for genuine understanding has spurred raptor enthusiasts, young and old. Fran and Hammi were there, and could be counted on, in 1966 when the Raptor Re- search Foundation, Inc. hatched. Fran and Hammi be- came life members in 1988. They have attended all of the Foundation’s Annual Meetings to date. Fran has served as Central Director; Frederick has served as a major ref- eree for many years, helped edit the seminal raptor man- agement techniques manual “Management of Raptors” and drew up the Foundation’s resolutions at almost every meeting. The Hamerstroms’ devotion to raptor biology was and is positively exemplary. They conducted most of their work on raptors using personal funds in off-hours from their regular positions. Their first major paper, “The Great Horned Owl and its prey in north-central United States” by Paul L. Errington, Frances Hamerstrom and Frederick Hamerstrom, was written when Frederick was a graduate Spring-Summer 1990 News and Reviews 33 student and Fran an undergraduate at Iowa State College. This paper won the Wildlife Society Award in 1940. As to early interests, Frederick writes, “I remember when I was a kid imitating soaring red-tails calling. None ever came down to me.” Fran feels that her lifelong prac- tice of falconry has heightened her skill as a raptor re- searcher. She took her first quarry with a kestrel in 1919. Fran and Hammi diligently kept on top of ornithological literature. Their bookshelves bend under the weight of volumes of European and North American journals. De- spite a fervent interest in what others wrote, the Ham- erstroms turned to the birds themselves for inspiration and ideas. Catching and marking raptors has always been of pas- sionate interest to the Hamerstroms. Their methods have been described in technical papers — and with far more detail and flavor in “Birding with a purpose: of raptors, gaboons and other creatures.” This book won the Council for Wisconsin Writers Award in 1984. Fran and Hammi have published 69 technical papers, a number of popular accounts, 1 poem on raptors, and the following books written by Fran and edited by Frederick: Birding with a purpose: of raptors, gaboons and oth- er creatures. Iowa State University Press. Harrier, hawk of the marshes: the hawk that is ruled by a mouse. Smithsonian Institution Press. Birds of prey of Wisconsin. Wisconsin Department of Natural Resources. Eagles, hawks, falcons and owls of America. Roberts Rinehart. An Eagle to the Sky. Lyons and Burford. Soon to re-appear is: Adventure of the stone man, a children’s book; Lyons and Burford. Bird trapping and bird banding, by Bub, Hamerstrom and Wuertz-Schaef- fer, is in press; Cornell University Press. Fran markets her own books and all proceeds go to research on birds of prey (Rt. 1, Box 448, Plainfield, WI 54966). Fran also writes books with messages other than raptor biology. Her latest, “Is she coming too? — Memoirs of a lady hunter,” recently took first place for the best non-fiction book in 1989, presented by the Council for Wisconsin Writers. The Hamerstrom’s international household is most re- markable. Their daughter, Elva, and son, Alan, have been exchanged with the kids of notable German biologists, among them Nobel laureate Konrad Lorenz. Fran and Frederick live in a stately old house modestly equipped with modern conveniences. Fran’s pies are legendary; on these a few gaboons have had their table manners polished. The house was always open to their many friends, not just those interested in raptors, but those with a genuine interest in music, life and humanity. 34 News and Reviews IN MEMOR1AM Frederick N. Hamerstrom 1909-1990 Frederick Hamerstrom, known to most people as “Hammi,” died in March in a log cabin overlooking coniferous forests and the rushing waters of Oregon’s North Umpqua River — a scene symbolic of the beauty and the wild landscape that he loved all his life. With Fran, his wife and teammate for 60 years, he pioneered in the field of wildlife research, delving into the ecology, life history, and management of prairie chickens, sharp-tailed grouse, pheasants, bobwhite quail, great horned owls, hawks, ospreys, sandhill cranes, white-tailed deer, and furbearers. He was one of the world’s foremost authorities on grouse, and is best known for his landmark research on prairie chickens and the development of a habitat management plan involving preserving a scatter pattern of grassland areas to provide essential life support — a strategy that saved the disappearing prairie chicken in Wisconsin and one that is used now in the management of other critical species and habitats elsewhere in the country and in the world. After graduating from Harvard with a degree in English Literature, he turned to his love of wildlife, and with Fran embarked on a career of wildlife research and management long before such a field was formally established. He earned an M.S. under Paul Errington at Iowa State University, and a Ph.D. under Aldo Leopold at the University of Wisconsin. His field studies took him to Necedah, Wisconsin as a project game manager for the Resettlement Administration, to the Edwin S. George Reserve of the University of Michigan as a field biologist, and to Portage County in central Wisconsin where he led the prairie grouse research for the Wisconsin Conservation Department and its successor the Wisconsin Department of Natural Resources for 23 years. His studies, speaking engagements, and participation in international meetings have taken him throughout the United States and Canada, Mexico, Europe, Russia, and Australia. Hammi worked closely with Fran in raptor research and helped form the Raptor Research Foundation. Besides working with eagles and a variety of hawks and owls in Wisconsin, they spent the last 17 winters trapping and banding Harris hawks in Texas, and carrying out nesting studies on ospreys in Mexico. He was not only a researcher, but an author (authored or coauthored with Fran 69 technical papers, and reviewed some 40 others) and a meticulous editor of countless writing efforts of students and peers alike. He was also an outstanding teacher, not in the classroom, but as he worked with students and colleagues in the field and patiently instructed thousands of volunteer observers about to enter the prairie chicken blinds. Many honors came to Hammi and Fran, among them the Wildlife Conservation Award of the National Wildlife Federation (1970), two Wildlife Society Publication Awards in 1940 and 1957, the Wisconsin Department of Natural Resources Bureau of Research Award (1973), and the United Peregrine Society Award (1980). Since 1972 both Hamerstroms have served as adjunct professors in the College of Natural Resources at the University of Wisconsin-Stevens Point. The name Frederick Hamerstrom will forever be in the annals of natural science. He was world-renowned, but he preferred to continue his simple life, without a lot of modern amenities, in tune with the land. His keen mind continually kept track of new research developments, helped young wildlife ecologists write in clear concise language, encouraged Fran (he was her best critic and editor) in capturing their life and times in her books. In unselfishly offering his help to so many others he often deferred his own personal agenda. There was an elegance about this soft-spoken gentle man, and a deep conviction about the integrity of the natural land community, with wildlife an integral part — for the role it played in the community, and for the thrill it provided in the hunt. His devotion to accurate wildlife research is shown in this anecdote that Fran tells. They had trapped and banded 1200 Harris hawks in Texas and examined 70 feathers on each one. “Darling, don’t you think we have enough?” “I don’t think so,” Hammi answered, “but we’re mighty close.” — Ruth L. Hine, Wisconsin Department of Natural Resources (retired), 3609 Nakoxna Rd., Madison, WI 53711. Spring-Summer 1990 News and Reviews 35 1 989 Leslie Brown Memorial Grant Recipients Gerard Malan Gerard Malan was awarded financial support from the Leslie Brown Memorial Grant to extend his study of the “Incidence and abundance of polyandry in the Pale Chanting Goshawk” in South Africa. The aim of this work is to elucidate the relative importance of potential selective factors in the evolution of polyandry in this species. Gerard Malan will compare the performance of trios with the performance of pairs, examining nest attendance, breeding success and hawk survival. In particular, he will be focusing on the role of habitat structure and prey availability as proximal causes of polyandry. Gerard Malan was born in 1959 in Cape Town. After finishing high school and military service, he enrolled at the University of Stellenbosch where he received a B.Sc. degree in Agriculture in 1984 and an honors degree in Nature Conservation in 1986. His honors research project dealt with the behavioral ecology of the Greywing Partridge. In 1986-1987 he worked as a research manager for a pharmaceutical company. In 1988, he began his graduate research on the Pale Chanting Goshawk at the Percy FitzPatrick Institute of African Ornithology, University of Cape Town. During his first year studying this southern African endemic raptor, he discovered that some of the “pairs” he was observing in the Little Karoo were actually cooperative, polyandrous trios. Anthony J. van Zyl was awarded support for his work on “Habitat utilization of the Red-breasted Sparrowhawk” along a 31 km stretch of the Tarka River in the Tarkastad District of South Africa. He has plans to continue his work for many years, hoping to elucidate the influence of habitat quality on philopatry, reproductive success and survival in this species. Anthony J. van Zyl became interested in birds at an early age. When the family moved to a rural sheep-farming area, he began studying and breeding racing pigeons. He also developed an interest in birds of prey and found Leslie Brown’s “Eagles of the world” and “Birds of prey, their biology and ecology” a great source of inspiration. He plotted Black Eagle nests in the district and checked the nests during school vacations. He was further stimulated by the ornithologist at the East London Museum, Carl Vernon, who took him on several field trips and encouraged his interest in birds of prey. When the family moved to the city of Pretoria, he began observing suburban birds such as the Crested Barbet. He also helped to protect a colony of Cape Vultures by going on patrol with the Vulture Study Group. With Alan Kemp of the Transvaal Museum, he started one of two Lanner Falcon breeding units in the country at that time and successfully raised Lanner Falcons. Anthony J. van Zyl obtained his B.Sc. at the University of Pretoria and completed his honors course at Rhodes University. He hopes to enroll for his M.Sc. degree at the University of Cape Town in 1990. At present he is involved in projects on Elephant-shrews, the Cape Sugarbirds, the Crested Barbet and the Red-breasted Sparrowhawk. He is a member of the Northern Transvaal Ornithological Society and the Zoological Society of South Africa. 36 News and Reviews Vol. 24, Nos. 1-2 The Hawk Mountain Sanctuary Association jointly awarded the 1990 Hawk Mountain-Zeiss Raptor Research Award to Eduardo E. Inigo Elias at the University of Florida and Karen L. Wiebe at the University of Saskatchewan. Inigo’s project was entitled “Effects of forest fragmentation on a tropical raptor community in the biosphere reserve of Montes Azules in the Lacandona region of Chiapas, Mexico” and Wiebe was studying “The effect of food supply on reproductive decisions and success in the American Kestrel.” The Hawk Mountain Sanctuary Association is now accepting applications for its fourteenth annual award to support student research on birds of prey. Support for this award is provided by Carl Zeiss Optical, Inc. Up to $2000 in funds are available and will be awarded to one or two recipients. To apply, a student applicant should submit a brief description of his or her research program (five pages maximum), a curriculum vitae , a budget summary including other funding anticipated, and two letters of recommendation to James C. Bednarz, Hawk Mountain Sanctuary Association, Route 2, Kempton, PA 19529, USA. The deadline for applications is 15 November 1990. The Asso- ciation’s board of directors will make a final decision in February 1991. Only undergraduate and graduate students in degree-granting institutions are eligible to apply. The awards will be granted on the basis of the project’s potential to improve understanding of raptor biology and its ultimate relevance to the conservation of raptor populations Applications from anywhere in the world will be considered. The National Wildlife Rehabilitators Association announces its small grants program. This program makes available two $1000 research grants in the field of wildlife rehabilitation. Each may be applied to one large project or several smaller research projects totaling less than $1000. Applicants must demonstrate financial need and submit a typewritten proposal that includes: name(s) and resume of personnel involved, objectives of the project, a brief description of how the project will be carried out, a brief literature review and an itemized budget. An annual report on progress is required. It is expected that those receiving NWRA support will present the results of their projects at an NWRA national meeting within 2 years of receipt of the grant. The deadline for submitting proposals for research grants is December 15 of each year. Recipients will be announced at the NWRA annual meeting in February and in writing. Proposals should be submitted to: Mark Pokras, Tufts University School of Veterinary Medicine, Wildlife Clinic, 200 Westboro Road, North Grafton, MA 01536. Opportunity exists for Graduate Study for two highly qualified students to begin a M.Sc. or Ph.D. program in the Department of Biology at the University of Saskatchewan. Successful applicants would be continuing long-term population studies of Merlins or Peregrine Falcons. Write L.W. Oliphant, Department of Veterinary Anatomy, University of Saskatchewan, Saskatoon, SK, CANADA S7N 0W0. Literature on falcons wanted! For the past 5 years I have been collecting literature on the Peregrine Falcon ( Falco peregnnus ) and related species (pelegrinoides , deiroleucus, fasciinucha and hypoleucos) along the lines of the “Working Bibliography of the Peregrine Falcon” which appeared in 1987. Presently, my collection comprises over 3000 titles. The aim is to assemble all available references on that subject worldwide, and build a central literature collection, which will be the basis for a planned monograph on the Peregrine Falcons of the world. Herein, all knowledge about this group of falcons will be summarized in a handbook-like fashion, similar to the work by Cramp & Simmons, “Birds of the Western Palearctic.” In order to complete this collection and keep it updated, I would be grateful for your support by sending me lists of publications, personal reprints (originals if possible), and papers from authors which are no longer needed. For those interested, the perusal of my collection is possible, and copies from publications can be obtained. — Dieter Schmidl, Peregrine Bibliography, D-8130 Seewiesen, FRG. Fran and Frederick Hamerstrom Award. In honor and recognition of Drs. Fran and Frederick Hamerstrom, the Raptor Research Foundation, Inc., has established an annual award to recognize significant contributions in raptor natural history and ecology. The Hamerstroms have contributed significantly to the understanding of raptor ecology and natural history through their long term ecological studies. Beginning in 1990, one award will be made annually. Spring-Summer 1990 News and Reviews 37 There are no restrictions to eligibility for this award, although active membership in the Raptor Research Foundation, Inc., is encouraged. To be considered for this award, candidates must be nominated by a member of the Raptor Research Foundation, Inc. Nominations should include: 1) the name, title, and address of both nominee and nominator, 2) the names of 3 persons qualified to evaluate the nominee’s scientific contribution to the study of raptor ecology and natural history, and 3) a brief summary of the scientific contribution of the nominee. Nominations will be evaluated on the basis of scientific contribution and productivity. An individual may not receive this award more than once. The award will consist of an engraved plaque to be presented at the Annual Meeting of the Raptor Research Foundation, Inc. Nominations must be submitted by 15 August of the year in which they are to be considered and sent to David E. Andersen, Chair, Fran and Frederick Hamerstrom Award, Minnesota Cooperative Fish and Wildlife Research Unit, 1980 Folwell Avenue, St. Paul, MN 55108 U.S.A. Leslie Brown Memorial Grant. In memory of one of the most inspired and productive raptor biologists, the Raptor Research Foundation, Inc., announces the availability of a grant, for up to $1,000. This grant is to provide financial assistance for research and/or the dissemination of information on birds of prey. Applicants must send a resume, specific study objectives, an account of how funds will be spent, and a statement indicating how the proposed work relates to other work by the applicant and to other sources of funds. Proposals concerning African raptors will receive highest priority between proposals of otherwise equal merit. A complete application must be received by September 15, 1991. Proposals, donations and inquiries about tax exempt contributions to the fund should be sent to Jeffrey L. Lincer, Chair, RRF Leslie Brown Memorial Fund, 4718 Dunn Drive, Sarasota, FL 34233 U.S.A. Erratum — Volume 23, Number 3, page 109, Figure 2, the darkened triangles represent unpaired males. 38 J Raptor Res. 24(1 -2):39-40 © 1990 The Raptor Research Foundation, Inc. Information for Contributors The Journal of Raptor Research welcomes reports of orig- inal research, review articles, letters to the editor, thesis abstracts and book reviews about the biology or conser- vation of diurnal and nocturnal birds of prey. Membership in The Raptor Research Foundation, Inc. is not a prereq- uisite for acceptance of contributions. Reports of research are subjected to a peer review to determine the suitability of the contribution for publication by the Journal. To be suitable for publication in the Journal, manuscripts must significantly enhance our understanding of the biology or conservation of raptors. Submit one original and three copies of a manuscript for consideration. Use one side of 215 by 280 mm (8V2 x 11 in.) or standard international (212 by 297 mm) white bond paper with 25 mm (1 in.) margins. Do not single space any part of the manuscript. Place author’s name and page number on the top, right-hand portion of every page of text. Submit all contributions to Josef K. Schmutz, Editor, The Journal of Raptor Research, Department of Biology, University of Saskatchewan, Saskatoon, SK., Canada, S7N owo. Research Reports Each manuscript should contain the following sections. A cover page should contain a title, the author’s full name(s) and address(es) of the institution where the re- search was done. Name and address should be centered on the page with names above the address. If the current address is different, indicate this via a footnote. Submit the current address on a separate page placed after the literature cited section. A short version of the title, not exceeding 35 characters, should be provided also. This will form the running head. If the first author is not also the corresponding author, or if a temporary address for correspondence is different, this should be stated also on this first page. An abstract of about 250 words should succinctly summarize the essence of all major findings. The abstract should be sufficiently informative to stand alone and be useful to abstracting services. The abstract should be on a separate page. The main body of the report should: define the question pursued in the introduction, describe study area and meth- ods, describe results and observations, interpret data in light of the question posed and vis-a-vis pertinent litera- ture, and acknowledge credit. Literature cited should be arranged chronologically in the text, using the author’s last name and year of publication. Separate two or more citations with a comma. If three or more authors are in- volved, use “Swainson et al. 1990.” In the literature cited section, complete citations should be arranged alphabeti- cally. Authors are to ensure that all citations are listed and match the original. When unpublished material is cited, provide initials (e.g., C.L. Bonaparte, pers. comm.) Tables should not duplicate material presented in the text or illustrations. Tables should be typewritten, double spaced throughout and be assigned consecutive Arabic nu- merals. Each table should be on a separate page and con- tain a short but informative heading. Footnotes to tables should be concise and identified with lower-case letters. Collect all figure legends on a separate page. Number figures consecutively in Arabic numerals. Include a key to symbols directly in the illustration unless the symbols re- quire a lengthy explanation. Each illustration should be centered on a single page. The name of the author and figure number, assigned consecutively using Arabic nu- merals, should be penciled on the back of each figure. Illustrations should be no smaller than final size and no larger than twice final size. The Journal of Raptor Research is published in a two column format with text 148 mm (5 13 / 6 in.) wide or 72 mm ( 2 13 / 6 in.) per column, and 195 mm {1% in.) deep. Line illustrations (e.g., maps, graphs, drawings) should be prepared in undiluted India ink and designed for a subsequent reduction by % to '/. Drawings should be on heavy weight, smooth finish, drafting paper (vellum) where possible. Use mechanical lettering devices, pressure trans- fer letters or calligraphy. Computer generated, dot-matrix print is acceptable for text if easily readable. For illustra- tions only a high quality laser printer will suffice. Lettering should be large enough so that it will be as large as text type (8-10 point) when reduced. Shading should consist of lines or dots that do not appear as solid tone when reduced. Black and white photographic illustrations may be used but these require that prior arrangements be made with the Editor and the Treasurer. Photographs should be glossy prints of good contrast and sharpness, preferably mounted on an artist’s mounting board not thicker than 1.5 mm (V l6 in.) and submitted in approximately the same size as they should appear in print. If an illustration is to contain two or more photographs, these should be mounted to- gether and abut with no white showing. Pictures should be identified and structures labeled using transfer letters/ arrows. As with line art, write the author’s name and the figure number on the back of the photograph. Authors should cite the scientific and common names (if used) for all species at first mention in both the abstract and again in the main body of the manuscript. Names for birds should follow the A.O.U. Check-list of North Amer- ican Birds (Sixth ed., 1983) or another authoritative source for other regions. Subspecific identification should be cited only when pertinent to the material presented. Metric units should be used for all measurements. Use the 24-hour clock (e.g., 0830 H and 2030 H) and “con- tinental” dating (e.g., 1 January 1990). Revised copies of accepted manuscripts must be re- 39 40 Vol. 24, Nos. 1-2 turned to the editor within 60 days. Manuscripts held longer will lose their priority and may be treated as new submissions. The editor should be notified if extenuating circumstances prevent a timely return of the manuscript. Proofs, typescript and reprint orders will be sent to the senior author unless another recipient is indicated. The author must check proofs carefully against the typescript and examine illustrations to ensure that none of the press- on material has been lost accidentally. Proofs must be forwarded to the Editor within 2 days of receipt. Correc- tions will be made without charge but revisions done by authors will be charged $2.50 per line reset. Thesis abstracts are published by the journal free of charge. Submit a title, date of publication, author’s name, institution and abstract. Letters to the editor are welcome and can include ob- servations with speculative interpretations, personal view- points or commentaries on published articles. Book reviews should include: title; author; date of publication; the num- ber of pages, tables, figures and appendices; publisher; cost; and author of review. Announcements of non-com- mercial raptor news and requests for assistance are also welcome. Advertisements are published free of charge pro- vided that a percentage of the proceeds is donated to The Raptor Research Foundation , Inc. Publication Cost To defray some of the considerable expense associated with publishing the Journal, The Raptor Research Foun- dation, Inc. expects authors to contribute through insti- tutional grants available. Authors who are able to pay the entire publishing cost can have their manuscripts pub- lished without delay. Authors who are members of the Foundation but do not have access to institutional grants or other funds may request that publishing cost be waived Authors of long manuscripts are especially encouraged to help defray publishing costs. It is unlikely that articles of more than 10 printed pages or 18 typewritten pages in- cluding tables and illustrations can be published without a significant contribution. Some costs, such as the retyping of single-spaced material and redrafting of figures, can not be waived. Reprint order forms and page costs will be forwarded to the authors along with the typescript and galley proofs The Raptor Research Foundation, Inc. will not waive the cost of reprints requested by authors. Payment for re- quested reprints must accompany the order form and both must be sent to the Editor. Authors employed by govern- ment agencies, universities or firms that will meet reprint and page charges may forward a statement to the Editor indicating intent to pay. Upon receipt of such a statement, reprints will be mailed to the author and the agency will be billed with the understanding that payment will be made within 30 days. All checks should be made payable to The Raptor Research Foundation, Inc. All personal con- tributions toward publication costs are tax-deductable in the United States. Copies of these instructions are available upon request from the Editor. THE RAPTOR RESEARCH FOUNDATION, INC. (Founded 1966) OFFICERS PRESIDENT: Richard J. Clark SECRETARY: James D. Fraser VICE-PRESIDENT: David M. Bird TREASURER: Jim Fitzpatrick BOARD OF DIRECTORS EASTERN DIRECTOR: Keith L. Bildstein CENTRAL DIRECTOR: Patrick T. Redig MOUNTAIN & PACIFIC DIRECTOR: Stephen W. Hoffman EAST CANADA DIRECTOR: David M. Bird WEST CANADA DIRECTOR: Paul C. James INTERNATIONAL DIRECTOR: Bernd U. Meyburg DIRECTOR AT LARGE #1: Michael W. Collopy DIRECTOR AT LARGE #2: Robert E. Kenward DIRECTOR AT LARGE #3: Jeffrey L. Lincer *#%***************** EDITORIAL STAFF EDITOR IN CHIEF: Josef K. Schmutz, Department of Biology, University of Saskatchewan, Sas- katoon, SK., Canada, S7N 0W0 ASSOCIATE EDITORS Keith L. Bildstein Susan B. Chaplin Charles J. Henny C. Stuart Houston Robert. E. Kenward Eudoxio Paredes-Ruiz Patricia P. Rabenold Patrick T. Redig EDITOR OF RRF KETTLE: Paul F. Steblein The Journal of Raptor Research is distributed quarterly to all current members. Original manuscripts dealing with the biology and conservation of diurnal and nocturnal birds of prey are welcomed from throughout the world, but must be written in English. Submissions can be in the form of research articles, letters to the editor, thesis abstracts and book reviews. Contributors should submit a typewritten original and three copies to the Editor. All submissions must be typewritten and double-spaced on one side of 215 by 280 mm (8 Vi x 11 in.) or standard international, white, bond paper, with 25 mm (1 in.) margins. The cover page should contain a title, the author’s full name(s) and address(es). Name and address should be centered on the cover page. If the current address is different, indicate this via a footnote. Submit the current address on a separate page placed after the literature cited section. A short version of the title, not exceeding 35 characters, should be provided for a running head. An abstract of about 250 words should accompany all research articles on a separate page. Tables, one to a page, should be double spaced throughout and be assigned consecutive Arabic numerals. Collect all figure legends on a separate page. Each illustration should be centered on a single page and be no smaller than final size and no larger than twice final size. The name of the author(s) and figure number, assigned consecutively using Arabic numerals, should be pencilled on the back of each figure. Names for birds should follow the A.O.U. Checklist of North American Birds (6th ed., 1983) or another authoritative source for other regions. Subspecific identification should be cited only when pertinent to the material presented. Metric units should be used for all measurements. Use the 24-hour clock (e.g., 0830 H and 2030 H) and “continental” dating (e.g., 1 January 1990). Refer to a recent issue of the journal for details in format. Explicit instructions and publication policy are outlined in “Information for contributors,” /. Raptor Res., Vol. 24(1-2), which is available from the editor.