Raptor Research A Quarterly Publication of The Raptor Research Foundation, Inc, Volume 19, Number 4, Winter 1985 fISSN 0099-9059) Contents TowAjtD Raptor Community EcouoGvr Behavior Bases of Assemblage Structure. Fabian M. Jak»k .107 Ov^’L Weights in the LrrERATUHEt A Review, John B. Dunning, Jr. ^ 115 Evaporative Water Loss in Captive Common Barn-Owls. Kii-k L Hamihor ^ ^ 1 PERTGRtNE FaLCON SeMEN: A QUANTiTATlVE AM? QUALITATIVE Examination, John H^icjHhan W'illiiim Burnhsm. , + ., + , + + ,,,1 25 PrairiI-; FaU:ON PrKV IN THE MojAVT DesERT. CaUFijRNIA. Dc»uglu A. Boyer. Jr. Perching AND Roosting Patterns of Raetors on Power Transmission- Towers IN Southeast Idaho and Southwest Wyoming. John c. Smith . . ^ * * 1 35 Short Communications Relatkmship Bciwrcn EYairk Falcon Nesting Phrnc»k7g>, Laiiiude and Ekvation. Rkhard N. Williams .... .139 Recapture of a Non-breeding Boreal OkI Two Years Later. Thotnaf W. Carpenter, d. 142 FalJ Raptor Concentration on Henryi Ijikc Hats. Daniel M Taylor and Charles H- Trost- . . .d . + . . .d . .I4S Bald Eagle {Hohaeftns leutoefpkaim^ Consumption of Harbor iwa| (Pluua viittlimst'} Hsenra tn Clflcier Bay, Alaska. John Calatnbokidi» and Grrtchm H. Striger 45 Barred Owl Hunting Insects. Arnold Drvinr. Dwight 5. Smith and Mark Stonlyr, 145 Northern Harrier EYedatlun on Greater Ftmrte Chlclcetis In Southtveu Mlsriouri. Brian Tolamd 146 News and REVtEws d , * 149, 150 The Raptor Research Found»dtin, lac. Provo, Utah THE RAPTOR RESEARCH FOUNDATION, INC. (Founded 1966) OFFICERS PRESIDENT: Jeffrey L. Linger, Office of the Scientific Advisor, 2086 Main Street, Sarasota, Florida 33577 VICE-PRESIDENT : Richard Clark, York College of Pennsylvania, Country Club Road, York, Pennsylvania 17405 SECRETARY: James D Fraser, Virginia Polytechnic Institute and State University, Cheatam Hall, Blacksburg, Virginia 24061 TREASURER: Gary E. Duke, Department of Veterinary Biology, 295K Animal Science/Veterinary Medicine Build- ing, University of Minnesota, St. Paul, Minnesota 55108 BOARD OF DIRECTORS EASTERN DIRECTOR: James A. Mosher, Appalachian Environmental Laboratory, University of Maryland, Frostburg State College Campus, Gunter Hall, Frostburg, Maryland 21532 CENTRAL DIRECTOR: Patrick T. Redig, Department of Veterinary Biology, 295 Animal Science/Veterinary Medicine Building, University of Minnesota, St. Paul, Minnesota 55108 MOUNTAIN & PACIFIC DIRECTOR: A1 Harmata, Department of Biology, Montana State University, Bozeman, Montana 59717 EAST CANADA DIRECTOR: David M. Bird, Macdonald Raptor Research Centre, Macdonald Campus of McGill University, 21,111 Lakeshore Road, Ste. Anne de Bellevue, Quebec H9X ICO WEST CANADA DIRECTOR: R. 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Subscription price to institutions and nonmembers is the same as regular member- ship. Single copies and back issues are available from the Treasurer. A Contributing Membership is $25, a Sustaining Membership is $100, and a Life Membership is $500. All contributions to The Raptor Research Foundation, Inc., are tax-deductible. Send requests for information concerning membership, subscriptions, special publications, or change of address to the Treasurer. Other communications may be routed through the appropriate Officer or Board member. All inquiries concerning the journal should be addressed to Clayton M. White, Editor, Raptor Research, Department of Zoology, 161 WIDB, Brigham Young University, Provo, Utah 84602, U.S. A. >K * iK * ♦ * * ♦ * He * « Xc ♦ * ♦ Published quarterly by The Raptor Research Foundation, Inc. Business Office: Gary E. Duke, Treasurer, Depart- ment of Veterinary Biology, 295K Animal Science/Veterinary Medicine Building, University of Minnesota, St. Paul, Minnesota 55108, U.S. A. Printed by Press Publishing Limited, Provo, Utah 84602. Second-class postage paid at Provo, Utah. Printed in U.S. A. Raptor Research A Quarterly Publication of The Raptor Research Foundation, Inc. Volume 19, Number 4, Winter 1985 (ISSN 0099-9059) Contents Toward Raptor Community Ecology: Behavior Bases of Assemblage Structure. Fabian M. jaksic .107 Owl Weights in the Literature: A Review. John B. Dunning, Jr 115 Evaporative Water Loss in Captive Common Barn-Owls. Kirk L. Hamilton 122 Peregrine Falcon Semen: A Quantitative and Qualitative Examination. John Hoolihan and William Burnham 125 Prairie Falcon Prey in the Mojave Desert, California. Douglas A. Boyce, Jr 128 Perching and Roosting Patterns of Raptors on Power Transmission Towers in Southeast Idaho and Southwest Wyoming. John c. Smith 135 Short Communications Relationship Between Prairie Falcon Nesting Phenology, Latitude and Elevation. Richard N. Williams 139 Recapture of a Non-breeding Boreal Owl Two Years Later, Thomas W. Carpenter, d . 142 Fall Raptor Concentration on Henrys Lake Flats. Daniel M, Taylor and Charles H. Trost 143 Bald Eagle {Haliaeetus leucocephalus) Consumption of Harbor Seal {Phoca vitulina) Placenta in Glacier Bay, Alaska. John Calambokidis and Gretchen H. Steiger 145 Barred Owl Hunting Insects. Arnold Devine, Dwight S. Smith and Mark Szantyr 145 Northern Harrier Predation on Greater Prairie Chickens in Southwest Missouri. Brian Toland 146 News and Reviews 149, 150 The Raptor Research Foundation, Iilc. Provo, Utah RAPTOR RESEARCH A QUARTERLY PUBLICATON OF THE RAPTOR RESEARCH FOUNDATION, INC. VoL. 19 Winter 1985 No. 4 TOWARD RAPTOR COMMUNITY ECOLOGY: BEHAVIOR BASES OF ASSEMBLAGE STRUCTURE Fabian M. Jaksic Abstract — Despite definite advantages in comparison to other model systems (e.g. assemblages of passerine birds and lizards), raptor community ecology is in its infancy. I discuss the adequacy of raptors as model predators for the study of the relationships between behavioral processes (agonistic interactions and hunting modes) and assemblage-level patterns (community structure). Community ecology studies of animals can be equated with the identification and quantification of the niche axes along which sympatric species appear to separate in order to reduce co-use of resources in limited supply. Schoener (1974) iden- tified habitat, food, and time as the axes that most frequently separate vertebrate predators (includ- ing arthropod consumers such as passerine birds and lizards, as well as carnivorous vertebrates). In- deed, the study of insectivorous passerine birds as model predators has contributed substantially to the development of community ecology, as attested by the pioneering studies of MacArthur (1972) and Cody (1974; Cody and Diamond 197.5); {see Strong et al. 1984 for more recent views). Subsequently, lizards have gained considerable importance as model predators {see Huey et al. 198.^ for an over- view of past and current contributions of her- petologists to community ecology). The early findings of Schoener {op. cit.), although disputed by some in terms of the underlying causes (see Strong et al. {op. cit.) for a confrontation of views), have by and large been held as verified. Both with passerine birds and lizards it has been shown that species often segregate along habitat (or mic- rohabitat) dimensions. However, the data dem- onstrating food segregation among these or- ganisms are suspect for reasons described below, and the adequacy of activity time as a niche differ- ence is under serious questioning (e.g., Jaksic 1982; Huey and Pianka 1983, Carothers and Jaksic 1984). Adding to the confusion is the fact that the three niche axes are usually correlated (segregation along one of them leads to segregation along another). thus making causality difficult to resolve. The reasons for these correlations are easy to infer. For example, the trophic structure (patterns of prey use) of sympatric assemblages, which is described on the basis of the diets of the component predators (taxonomic composition, diversity, interspecific similarity, mean prey size, etc.) is only the outcome of behavioral processes occurring at the level of the local population. These processes involve not only prey selection, but also habitat preferences by the individual predators, their activity times, foraging modes and efficiencies, as well as morphological, physiological, and ecological constraints. The gap between the summary description of food-niche patterns in predator assemblages and the foraging mode of individual predator species has recently been bridged for passerine birds (Eck- hardt 1979; Robinson and Holmes 1982) and lizards (Huey and Pianka 1981). In my view, how- ever, these two groups of organisms, which seem to be very suitable for studies of habitat preferences and microhabitat partitioning, are less suitable for the study of prey selection and food segregation. First, prey in their diet often are identifiable only to the ordinal level, and with some difficulty (at least for ornithologists) to the familial level, which repre- sents an important shortcoming. Greene and Jaksic (1983) have shown that in dietary studies of pred- ators identification of prey at the ordinal level (customarily used in passerine and lizard diet studies) underestimates diet diversity and overes- timates diet similarity calculated at the species level of prey identification. Further, Greene and Jaksic {op. cit. ) have shown that these biases arise in unpre- 107 Raptor Research 19 (4):107-112 108 Fabian M. Jaksic VoL. 19, No. 4 dictable fashion, so that no reliable correction fac- tors can be introduced in the computation of di- etary statistics and consequently the food-niche patterns so far documented for passerine birds and lizards are suspect. A second shortcoming of using passerine birds and lizards as model predators is that they are sub- ject to predation themselves. This renders it dif- ficult to resolve whether they maximize some prey selection function or compromise the use of opti- mal prey by minimizing predation risks (an impor- tant consideration in terms of optimal foraging theory: see Pyke et al. 1977). These two shortcomings become especially appar- ent if one’s intention is to correlate food-niche statistics (for whole predator assemblages) with the foraging modes of the constituent species. It is un- fortunate that this is so, because I think that the question of how foraging mode is reflected in the trophic structure of sympatric predators is an im- portant one in community ecology. Provided that neither passerine birds nor lizards seem particu- larly adequate model predators for such an en- quiry, I contend that raptors (Order Falconiformes and Strigiformes) may help clarify the relationships between “basal” behavioral processes and “epiphenomenic” patterns of assemblage structure. In the following sections I discuss the pros and cons of using raptor assemblages as models for behaviorally-based community analyses and pro- pose tbe type of information to be gathered. Raptor Assemblages as Model Systems Until recently, raptors have been neglected as model predators in community ecology. Neverthe- less they have much to offer toward the clarification of niche relationships among sympatric consumers. Segregation of raptors along the habitat axis has been documented both intra- and inters pec ifically (e.g., Newton 1979; Schmutz et al. 1980; Nilsson et al. 1982; Janes 1984), but this segregation does not clearly result in access to different prey popula- tions. Consequently, reduction of exploitative competition seems an unlikely cause for such phenomenon, nor does use of the same hunting habitat lead to compensatory differentiation along the food axis (Schnell 1968; Baker and Brooks 1981; Steenhof and Kochert 1985) which may be interpreted as resulting from the functional re- sponse of essentially opportunistic raptors to high prey densities (Jaksic et al. 1981 ; Jaksic and Braker 1983; Erlinge et al. 1984). In my impression, where habitat separation is observed among raptors, the proximate cause lies on agonistic interactions — a claim for which both direct (Rudolph 1978; Janes {op. cit.) and indirect evidence exists {see Newton 1979; Jaksic 1982; Mikkola 1983, for summaries of predation among raptors, an extreme form of agonistic interaction). Consequently, the use of exclusive ranges by raptors relate to reduction of interference rather than of exploitative competi- tion. Something similar may be said of the causes of temporal segregation. Jaksic (1982) documented that diurnal and nocturnal raptors do not differ enough in prey use (i.e., their diets are too similar) to justify the view that they reduce exploitative competition by differing in activity period (similar conclusions were reached by Huey and Pianka 1983). In fact, Jaksic {op. cit.), based on circumstan- tial evidence, contended that reduction of agonistic interactions was the likely target of such temporal segregation of activity. Carothers and Jaksic {op. cit.), have elaborated this point on more theoretical grounds, and for a variety of other organisms. Rudolph {op. cit.) documented temporal segrega- tion between two sympatric owl species, mediated by predation of one upon the other. Notice, then, that where interspecific segregation of raptors along habitat and time dimensions has been re- ported, tbe proximate factor may well be aggressive exclusion rather than peaceful preemption of specific resources as accomplished by differential efficiencies in the exploitation of portions of the niche axes. The latter has been the general as- sumption underlying most studies of community ecology, and I think that the study of raptor as- semblages can contribute greatly to the under- standing of the alternative mechanism (interfer- ence competition) in generating the structure of communities. What about food partitioning? Studies ranging in generality from selected pairs of species through small groups of related raptors to entire as- semblages have rendered varied conclusions (e.g., Schmutz et al. {op. cif.); Jaksic and Braker {op. cit.); Knight and Jackman 1984; Marks and Marti 1984). Results indicate that sometimes prey is partitioned via size differences between raptors (accipiters are good examples of this: see Storer 1966; Opdam 1975; Schoener 1984), and that sometimes raptors differing greatly in body size take essentially the Winter 1985 Raptor Community Ecology 109 same prey (Schmutz et al. (pp. cit.); Jaksic 1983; Jaksic and Braker (op. cit.)). There is a tendency, though, for particular raptor groups to “specialize” on certain general prey categories (e.g., kites and harriers on small mammals and birds, small falcons on insects, larger falcons on medium-sized mam- mals and birds, eagles on hares; buteonines appear very catholic in diet). These different groups of raptors share in common similar morphologies and hunting modes {see Jaksic and Carothers 1985), which leads me to suggest that the reported trophic structure of the few raptor assemblages so far quantified Jaksic 1982, 1983; and Jaksic and Braker {op. cit . )) somehow reflects those similarities. 1 do not exactly share the view of Ricklefs and associates (e.g., Ricklefs and Cox 1977; Bierregaard 1978; Ricklefs and Travis 1980) that it is not neces- sary to go to the field for studying community ecol- ogy: morphologic analyses suffice. Instead, I es- pouse the view {see also Steenhof and Kochert {op. cit.)) that the study of the hunting behavior of rap- tors will tell us much about the way assemblages are structured. That is, how behavioral processes result in community patterns. In comparison to both passerine birds and lizards, the scrutiny of raptor food-niche relation- ships is facilitated by their greater conspicuousness and use of prominent roosting and nesting sites, where detailed information on their diet can be obtained. However, they also show some shortcomings as model predators. Despite the fact of generally being top predators in terrestrial ecosystems, raptors are not entirely free of preda- tion. Some species are indeed frequently preyed upon by other raptors (.vrr Newton op. cit.; Mikkola op. cit. for summaries), and thus the study of raptor assemblages does not completely eliminate the dual constraints of energy maximization and mortality minimization. But at least in comparison to pas- serine birds and lizards, raptor behavior should, on the average, be less affected by predation. The problem of the taxonomic resolution of prey (Greene and Jaksic {op.cit.)) is important in raptors that prey primarily on insects; but essentially car- nivorous raptors abound, and their vertebrate prey is easily identifiable to the species level, particularly if mammalian {see Errington 1930; Burton 1973, for examples). In comparison to passerine birds and lizards, then, accurate estimates can be made of raptor diet diversity (= breadth) and interspecific similarity (= overlap). In addition, open-terrain raptors are relatively large, conspicuous birds whose time budget, hunting mode, and hunting success, can be quantified with minimal equipment {see Rudebeck 1950, 1951; Warner and Rudd 1975; Tarboton 1978; Wakeley 1978a, 1978b; Mendel- sohn 1982; Rudolph 1982). Consequently, the proportional use that raptors make of differing hunting modes can be recorded and examined in light of their diets and hunting success in different habitat types. In sum, at least as compared to pas- serine birds and lizards, raptor assemblages are ex- cellent candidates for the study of food-niche re- lationships of sympatric predators as related to the hunting behavior of the component species. In the following section I propose the type of information to be gathered for such an aim. Information Required to Assess Community-Ecological Correlates of Raptor Hunting Behavior 1. The use that sympatric raptors make of different hunting techniques. — Raptor hunting activities can be dichotomized as either perch- or aerial-hunting. Within this second category, at least four techniques can be recognized: a) hovering flight: a stationary flight that may or may not take advantage of the wind conditions; used by small falcons (e.g., Falco sparverius), small kites (e.g., Elanus spp.), and by the Burrowing Owl {Athene cunicularia); b) cruising flight: a high-speed, low- altitude flight; used by large falcons (e.g., Falco mexicanus) and accipiters {Accipiter spp.); c) quar- tering flight: a low-speed, to-and-fro flight; used by harriers {Circus spp.), and some owls {Asio flam- meus, Tyto alba)] and d) soaring flight: low-speed, high-altitude flight that takes advanage of either thermal or obstruction air currents; used by eagles {e.g.,Aquila spp.) and buteonine hawks {Buteo spp.), among others. More detailed descriptions of these hunting flight techniques can be seen in Brown and Amadon (1968), Warner and Rudd (1975), Everett (1977), Tarboton (1978), Wakeley (1978b), Cade (1982), Rudolph (1982), Collopy (1983a), and Col- lopy and Koplin (1983). Recognition of these five techniques seems necessary because there are indi- cations that they facilitate access to different habitats and prey types, and also because their energetic costs differ (j^^ Jaksic and Carothers 1985 for a selective summary). The time allocated to the different hunting techniques by sympatric raptors should be evaluated and, noting the prey captured no Fabian M. Jaksic VoL. 19, No. 4 with each, the ecological consequences of raptor use of differing techniques assessed. 2. The use that sympatric raptors make of dif- ferent habitat types while hunting. — Here, it is necessary to evaluate the time spent by raptors hunting in different habitat types {see Wakeley 1978a; Bechard 1982, for examples), because it is likely that prey availabilities differ among habitats {see USDl 1979 et seq.; Baker and Brooks 1981; Bechard 1982, for such findings). Perhaps only broad categories of habitat use by raptors need to be recognized, depending on the physiognomy and landscape units that characterize the study site. For interesting examples of ad-hoc habitat categoriza- tions USDl (1979 et seq.). 3. The hunting success of sympatric raptors in different hahitat types and in using different hunting techniques. — The hunting success can be estimated as the number of successful prey strikes over the total hunting time spent by the different raptors. Unsuccessful prey strikes also should be counted to determine the hunting effi- ciency (successful strikes/total strikes with known outcome) of raptors using different hunting techniques (Collopy 1983a; Collopy and Koplin {op. cit.)). The prey captured ideally should be iden- tified to the species level with the aid of adequate viewing devices. Direct observations are possible especially during the breeding season, when birds can be tracked to the nest after a successful prey strike, and the prey can be identified there if not at the capture site (e.g., Collopy 1983h). By focusing attention on open-terrain raptors, the prey cap- tured in different parts of the habitat can be iden- tified (e.g., Mendelsohn {op. cit.)). 4. The presumable clues that sympatric raptors use in choosing hunting habitats. — This is unde- niably the most difficult part of the proposed re- search protocol. Judging from recent studies (e.g., Jaksic etal. 1981, 1982; Jaksic and Braker (o/i. cit.)-, Erlinge et al. {op. cit.)), generalist raptors appear to take prey in about the order of their respective availabilities in the field. Within characteristic upper and lower size thresholds scaled to the sizes of the individual raptor (whatever their abundance, hares are unavailable prey for American Kestrels the same way that grasshoppiers are for Golden Eagles). Because prey are taken by raptors on a one-by-one basis, numerical estimates of the abun- dance of individual prey may well serve as a crude estimate of their availability in the different habitat types recognized in the study site {see Baker and Brooks 1981; and Bechard 1982, for cautionary notes). Many techniques exist that can be used (e.g., Giles 1971), and examples of their applicability and relative success can be found in USDl ( 1 979 et seq.). An additional characteristic of the prey species which may be important in affecting their selection by — or vulnerability to — raptors is their mobility (e.g., Huey and Pianka 1981). This feature can be evaluated as the average displacement in meters per activity period, with the specifics of the mea- surement depending on the type of prey. Ideally, a vulnerability index for the different prey species at the study site could perhaps be devised by combin- ing prey characteristics such as density, spatial dis- tribution (clumped, random, regular), micro- habitat use, mobility, size, conspicuousness, etc. How to compute such a complex index I cannot figure out, because vulnerability is not an inherent feature of the prey and should vary relative to rap- tor characteristics (size, hahitat preferences, and hunting mode). Concluding Remarks The study of assemblage-level correlates of hunting behavior in raptors should prove il- luminating for a number of important questions in community ecology: To what extent does the trophic structure of predator assemblages reflect the hunting behaviors of the component species?, and — more specifically — provided that fal- coniforms and strigiforms replace each other dur- ing the daily cycle, is the similar trophic structure of these raptor assemblages (Jaksic 1983) based on behavioral similarities in the hunting modes of their respective constituent species? To what extent do the differing hunting modes of sympatric pre- dators facilitate their coexistence through reduc- tion of co-use of food resources (exploitative com- petition)? What is the influence of interspecific agonistic interactions (interference competition) in the selection of hunting habitats and of hunting modes by sympatric raptors? Autecological studies of raptors are abundant {see Clark et al. 1978 for a bibliography; Bunn et al. 1982, and Watson 1977, for specific studies), and raptor population ecology has long reached its maturity (see Newton 1979; Mikkola 1983, and re- ferences therein). However, community ecology of raptors is still in its infancy (see Jaksic and Braker 1983 for a cursory review). Given that raptors com- Winter 1985 Raptor Community Ecology 111 pare more than favorably to other organisms (pas- serine birds, lizards) as model predators, I think the time is ripe for exploring this much neglected as- pect of raptor ecology. Acknowledgments I thank Keith L. Bildstein, Tom J. Cade, John H. Carothers, Michael W. Collopy, Eduardo R. Fuentes, Harry W. Greene, Jef- frey L. Lincer, David T. Rogers, Jr., Clayton M. White, Stephen A. Nesbitt, and an anonymous reviewer for critically reading dif- ferent versions of the manuscript. 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The choice of prey and modes of hunting of predatory birds with special reference to their selective effect. Oikos 3:200-229. Rudolph, S.G. 1978. Predation ecology of coexisting Great Horned and Barn Owls. Wilson Bull. 90:134- 137. . 1982. Foraging strategies of Ameri- can Kestrels during breeding. Ecology 63:1268-1276. ScHMUTZ, J.K., S.M. ScHMUTZ AND D.A. BoAG. 1980. Coexistence of three species of hawks {Buteo spp.) in the prairie-parkland ecotone. Can J. Zool. 58:1075-1089. ScHNELL, G.D. 1968. Differential habitat utilization by wintering Rough-legged and Red-tailed Hawks. Con- dor 70:373-377. ScHOENER, T.W. 1974. Resource partitioning in ecologi- cal communities. Science 185:27-39. . 1984. Size differences among sympatric, bird- eating hawks: a worldwide survey. Pp. 254-278 In Strong, D.R., D. Simberloff, L.G. Abele and A.B Thistle (Eds) Ecological communities: conceptual is- sues and the evidence. Princeton University Press, Princeton, NJ. Steenhof, K. and M.N. Kochert. 1985. Dietary shifts of sympatric buteos during a prey decline Oecologia: 66:6-16. Storer, R.W. 1966. Sexual dimorphism and food habits in three North American accipiters. Auk 83:423-436. Strong, D.R., D. Simberloff, L.G. Abele and A.B. This- tle. 1984. Ecological communities: conceptual is- sues and the evidence. Princeton Univ. Press, Prince- ton, NJ. Tarboton, W.R. 1978. Hunting and the energy budget of the Black-shouldered Kite. Condor 80:88-91. U.S. Dept, of the Interior. 1979 Et Seq. Snake River Birds of Prey Special Research Report to the Secretary of the Interior. Bureau of Land Mgt., Boise, Idaho. Wakeley, J.S. 1978a. Factors affecting the use of hunt- ing sites by Ferruginous Hawks Condor 80:316-326. , 1978b. Hunting methods and factors affecting their use by Ferruginous Hawks. Condor 80:327-333. Warner, J.S. and R.L. Rudd. 1975. Hunting by the White-tailed Kite {Elanus leucurus). Condor 77:226-230 Watson, D. 1977. The Hen Harrier, T.& A.D. Poyser Limited, Berkhamsted, Hertfordshire. Departamento de Biologia Ambiental, Pontificia Universidad Catolica de Chile, Casilla 114-D, Santiago, Chile. First received 7 March 1984; Accepted 20 April 1985 OWL WEIGHTS IN THE LITERATURE: A REVIEW John B. Dunning, Jr. Abstract - Published mean body weights of 1 8 species of North American owls are presented and reviewed. Adequate data are lacking for virtually all species. A pattern of increased weight lability in small owl species is suggested by several studies of captive and wild birds. One source with large samples of weight data is rejected as its means deviate from virtually all other published sources. Mean body weight is an important descriptive statistic used in many avian studies. Often, how- ever, researchers do not handle large numbers of individual birds, and must rely on published mean weights for the species they are studying. This is especially true in the case of owls, which are difficult to capture and weigh in large numbers. In the course of compiling available weight data for all North American birds, I searched the literature for owl weights and noted some inconsistencies. The purpose of this paper is to review the published data, assess the reliability of different sources, and discuss general trends apparent from the data. Major Sources Most studies reporting owl weights contain very small samples, often only a single weight. Two sources do present weights of all or almost all North American species. Earhart and Johnson (1970) (hereafter, E&J) analyzed patterns of size di- morphism and food habits in owls. They presented weights (Table 1) and wing lengths for all North American owls except the Elf Owl {Micrathene whit- neyi). E&J included 5 subspecies of the Great Horned Owl {Bubo virginianus) and 8 subspecies of fjastern and Western Screech-Owl {Otus asio and O. kennkottii). These weights were compiled from various museum collections. The sample sizes were often the largest reliable weight samples available for each species. E&J used these data to calculate the degree of sexual dimorphism for each species, and examined how various ecological parameters vary with body size. Snyder and Wiley (1976) also used this same data set to examine food stress and female nest defense as factors influencing reversed sexual dimorphism in hawks and owls. The data presented in E&J included sample size, mean and range for both sexes. The second source with a large series of owl weights was Karalus and Eckert (1974) (hereafter, K&E). This is essentially a “coffee table book” with species accounts of all North American owls. It dif- fers from the usual book of this type by including detailed information of species’ and subspecies’ range, weight, linear measurements, voice and general behavior. The measurements initially seem attractive since they are based on large samples, sometimes larger than E&J (Table 1). Unfortu- nately, the data in this book appear to be completely unreliable. The acknowledgments imply that most measurements were taken from museum speci- mens, but no sources are cited. K&E also presented sample size, mean and range for at least 1 sub- species of each species, while an “average weight” was given for most other subspecies. Species Accounts Tyto alba — Single weights of the Common Barn-Owl are given in Imler (1937) (475g, unsexed fall bird from Kansas) and Stewart (1952) (457g, unsexed fall bird from Ohio). Jackson and Dakin (1982) gave weights of 2 c? J* from Mississippi (492, 512g). Poole (1938) reported the mean of 2 birds as 505g, while Haverschmidt (1948) listed the weights of 1 c? (485g) and 3 $ 9 (446, 498, 558g) from Surinam. Hartman (1961) collected 4 9 $ (X = 516g) and 4 cf J (X = 439g). His birds were from Panama, Florida and Ohio, so weights cannot be ascribed to any one locality with confidence. Marks and Marti ( 1984) gave the mean of 78 birds as 5 1 1 g. All these weights were within the range given by E&J. Large samples are in Steenhof (1983) and Marti and Wagner (1985) (Table 1). Steenhof (1983) cited unpublished data. Her means were substantially higher, but within the range presented in E&J. Marti and Wagner (1985) presented data for live (Table 1), trauma-killed, and starved owls from northern Utah in winter. Both starved (9 X = 392g, N ^ 25; c? X ^ 335g, N = 28) and trauma- killed (9 X = 434g, N = 14; d' X = 361g, N = 7) birds weighed less than live trapped owls. In addi- tion, the starved birds weighed less than the trauma-killed, demonstrating that the manner in which weight data is collected can affect means re- corded for a sample. K&E’s data were similar to 113 Raptor Research 19 (4):1 13-121 Table 1. Large samples of published weights (g) for North American owls. Data are presented as: X (sample size) range. 114 John B. Dunning, Jr. VoL. 19, No. 4 o c Oi O! Q. E u > (M CD 02 5 Pi C P s: c o ^ !D ID O 00 CD CO ^ ^ 00 ^ ^ on o o d ® ^ -H to ^ 1 > CD iD ID dT CD d CD '-'i ^ r- xD O) CD ID ^ — Tt- 'Ct^ 00 00 02 05 o Q 05 cjj on - ^ ° 05 CD - O c ST o Slf 0, oo" t5T on 05 ID c ID I> ra on ID ^ ^ I-H I-H C CT3 ^ CD on ^ ^ ^ ^ .u _y ^ ^ O la 05 O CD CD CD CD C\r 'tT ^ ot ^ w C^ on 00 t' o ID >D on CM 00 ^ on on CM CM i) V > > > > > CM CM a 03 CC! D D D CD CM CD CD CD CD CD OO o CD on CM CM CM CM < tJi O O oo iD on CD 00 O on CM o o — — CM CM CH ^3 CH ^ 05 o 05 on CD o 00 o oo b^ o 00 O o CD xD 00 O CD CD CM XD 1> o o CM CM cn 05 XD 00 on on o CM. CM XD CM b^ CD XD XD 00 00 on CD xD 05 CD bc o O' CM CD J> xD on CM CM CM ID XD on CM CM CM xD CD CD CM CM CM o xD »D xD XD d CM 05 CD ID ■of CD in iO 05 CM d d d d o6 CD o bc 00 CD CM d o d 00 05 ' CM d CO CM 00 XD on o o on o d 05 OO 00 00 00 CM on CM »D 1—1 05 05 05 QO 1— 1 >— 1 f—f .. , , CD ^ 1> V, CD !0 V. ^ ^ ^ ' ^ ' . . on" CM CM o 05 CM 00 00 on CM 1-H CD s cc 00 o CM CM o 00 XD , — 1 on o o CD OB' CM CM CM CD 00 CM on on on 1-H CM 'Cf CM ' — ' ^ ^ ' — ' CM CM 0 CM XD CD 05 00 00 xn bc CM CM o CM o xD iC CM on CD CM r- CM XD on CD . — 1 in XD CM bc b^ 05 D~‘ on 00 CD cn CM m on CM . — 1 00 XD XD 'Cf XD on CM d XD CM O' on m on 05 Tf XD XD ’—1 — — — — — 05 00 >—1 05 05 CH ^3 Ot o 'b CH ’b o *b Of Of "b Of cb Of bi Of ’b Of »b Of b CH b Of b Of b u S3 asio naeviu mccallii o s S cinerascens o .«o s e ■« s quercinus •a f- -s; .Co e ' virginianu virginianu virginianu occidentals pacificus pallescens § CS 3 "se -ai s s . V. . V. 6 d d 6 d 6 d d 05 =Q cq cq CQ CQ (Table 1 continued) (Continuation of Table 1.) Winter 1985 Owl Weights 115 o X H O X u w z; o z X o ' — } < X ai < W a B X o CJ S o z; H o c tri m cu ^ ^ I If) c o C" CJ ” O ^ ^ O N) ot ’io o o CJ cf 00 CO r-; 00 CJ 0 O) 00 on CJ on CD 00 eft CO CO cd 06 in CO CM CJ J> CJ CM in T 00 00 CO d CM CJ m 4 4 CD 4 in in o CJ o CJ CD CO on 4 on r- If) CO 'j O) 00 s 00" od m CJ on G 74 OS' o G CJ CO □6" 00" CM m CJ 'cD cn t> CO m CJ 4 d ci 06 cd If) 0 CJ CJ 'tD 00 CJ CJ CJ CM OH *10 CH 'b OJ CH CH CH ^ ^ If) o — in C) ^ m m cc y:> ^ m 00 on on nf CM 00 00 — 00 o on on on on m t> »n cf t> O) cSj G on CJ CT) on CJ t> CJ on on o O) O) O CD CJ CJ cf ■ on , 00 m CO ^ ^ CO ^ ‘ ‘ CO , CJ CJ CJ ^ CO CO C) o O) o on in on in on ^ CD _ 00 CJ CJ oo —I CJ ^ ^ CO on 00 CO L' m on 00 CJ on CJ OJ'bcH’boj'boj'bot^ CJ CO S ^ r~ Tf m ^ ■V|Oor-cj)L- § ^ CM CO S f:, CO in CO Tt- co'nmCT)P‘^“^. 0)cocfCT)on'-Hin'-^ rt^onCJT'COJMCO CH-'bcH-'^o+’bot^ in 00 00 CJ -H CJ o ^ to O) o 00 00 m m ^ in m cf nf O -H — L- O 00 ^ CO CO nf CD in CM on ^ CD on GO o on CO m 00 CO 0'bcH-N)CH-^o+’bcH^ CJ Ti- in oc Tf .-H to on on 'T on O C30 t:D CO ^ n- 00 o CJ -H CM CJ 00 OB' O CJ on CJ CJ m 00 m ic cf r~ ^ CM CJ on on Aegoliusfunereus $ 140(4) 121-160 $ 224(23) 199-235 $ 167(96) 126-194 Glutz et al. 1979 d' 102(5) 85-119 c? 211(26) 193-227 d 101(74) 90-1 13 Aegolius acadKus $ 90.8(18) 65-124 $ 107(31) 87.9-124 U 91.2(68) 72-1 12 Mueller & Berger 1967 d 74.9(27) 54-96 d 102(37) 84.3-119 116 John B. Dunning, Jr. VoL. 19, No. 4 E&J for females, but underestimated the male weight by 13%. As is true of most other species, too few data have been published to examine geo- graphical variation. Otus flammeolus — Johnson and Russell (1962) presented mean weights for 13 Flammulated Owls from California and Nevada (Table 1). The mean for 11 c? c? is similar to E&J’s mean for 56 c? . The female mean in Johnson and Russell is substantially higher, but sample sizes are small. K&E’s data are widely divergent from both of the above sources, deviating from E&J by 130 - 140%. Otus asio and O. kennicottii — Eastern and West- ern Screech-Owls contain 16 subspecies combined that are widely divergent in size (A.O.U. 1957, but see Marshall 1967). The only source covering all 16 subspecies is K&E, but as has been shown for most other species, these weights are at odds with virtu- ally all other available sources. E&J provided weights for 2 subspecies of Eastern Screech-Owl {naevius, mccallii) and 5 subspecies of Western Screech-Owl {inyoensis, cinerascens, kennicottii, ben- direi, quercinus). A large degree of geographic vari- ation is apparent from this data set. Other sources of screech-owl weights are few. I found no data for aikeni, asio, brewsteri, hasbroucki, maxwelliae, and Johnson and Russell (1962) collected 1 9 macfarlanei in California weighing 177g. Miller and Miller (1951) presented data from Arizona and California for 3 southwestern sub- species: yumanensis (6 c?cf, X = 103g± 1 1 .4S.D.), inyoensis (2 9 9 , X = 157g); 8 o o Q. o > UJ Metabolism Chamber Tempi C) Figure 1 : Water loss (mg H20/g-h) of 6 captive barn owls. Eighty-five measurements from 6 captive barn owls showed that water loss (mg H20/g-h) increased significantly (P < 0.001) as ambient temp increased (Fig. 1). Recent studies by Wunder (1979), Weath- ers (1979, 1981), and Dawson (1982) have examined climatic adaptation, physiological ther- moregulation and water loss from birds and the data exhibited by the barn owl does not deviate from established patterns. Water loss of barn owls at ambient temp from 0-20°C is not different than data for non-incubating pigeons (Lophophops fer- ruginea) (Dawson and Bennett 1973) or Burrowing Owls {Athene cunicularia) (Coulombe 1970). Coulombe (1970), Dawson and Bennett (1973) and Weathers (1981) have shown that the pattern of evaporative water loss of birds is an exponential function. However, water loss is essentially linear until approximately 35-40°C at which time birds become heat-stressed (Dawson 1982) and the water loss increased exponentially. This is also seen in Figure 1 ; at temp that mimics incubation temp (up to 30°C) water loss of barn owls is fairly linear and not very substantial. However, barn owls in Utah do not experience nestbox temp greater than 32°C during incubation (Hamilton 1982); therefore, the barn owl in Utah may be able to conduct incubation without an apparent heat stress. In summary, birds must contend with numerous environmental stresses during incubation, one of which is heat stress. Some birds utilize roost sites with low heat loads (Barrows 1981), while other incubating birds use postural thermoregulatory behavior to reduce heat stress (Lustick et al. 1978, 1979; Bartholomew and Dawson 1979). The barn owl may escape heat stress problems during incu- bation by using nestboxes and by choosing a loca- tion where high ambient temp does not occur. Acknowledgments This paper is part of a dissertation submitted to the Department of Biology at Utah State University in partial fulfillment of the requirements for the Ph.D. degree. I thank members of my graduate committee: Drs. J.A. Gessaman, K.L. Dixon, R.T. San- ders, R.P. Sharma and L.C. Ellis, I also thank Dr. A.B. Hamilton for her help and support through the years. Thanks to Drs. H.E. Dziuk, J.A. Mosher and one anonymous referee for reviewing an earlier version of this manuscript. Thanks to Ms. P. Hornbeck and Ms. J. Thorp for secretarial assistance. This study was funded in part by an Edwards H. and Winnie H. Smith Fellowship from the Welder Wildlife Foundation (Dr. J.G. Teer, Director), a Sigma Xi Grant-in-Aid of Research award, and the Ecology Center, Utah State University (Dr. F. Wagner, Director). This is Welder Wildlife Foundation Contribution No. 282. 124 Kirk L. Hamilton VoL. 19, No. 4 Literature Cited Barrows, C.W. 1981. Roost selection by Spotted Owls: an adaptation to heat stress. Condor 83:302-309. Bartholomew, G.A. and W.R. Dawson. 1979. Ther- moregulatory behavior during incubation in Heer- mann’s Gulls. Physiol. Zool. 52:422-437. Bartholomew, G.A., R.C. Lasiewski and E.C. Craw- ford. 1968. Patterns of panting and gular flutter in Cormorants, Pelicans, Owls, and Doves. Condor 70:31-34. CouLOMBE, H.N. 1970. Physiological and physical as- fiectsof temperature regulation in the Burrowing Owl Speotyto cunkularia. Comp. Biochem. Physiol. 35:307-337. Dawson, W.R. 1982. Evaporative losses of water by birds. Comp. Biochem. Physiol. 71 A:495-509. Dawson, W.R. and A.F. Bennett. 1973. Roles of metabolic level and temperature regulation in the ad- justment of Western Plumed Pigeons (Lophophops fer- ruginea) to desert conditions. Comp. Biochem. Physiol. 44A:249-266. Hamilton, K.L. 1982. The energetic cost of incubation and bioenergetics of the Bam Owl. Ph.D. Thesis. Utah State University, Logan, 122 pp. Lustick, S., B. Battersby and M. Kelty. 1978. Be- havioral thermoregulation: orientation towards the sun in Herring Gulls. Science 200:81-83. . 1979. Effectsof insulation on juvenile Herring Gull energetics and behavior. Ecology 60:673-678. Marti, C.D., P.W. Wagner and K.W. Denne. 1979. Nest boxes for the management of Barn Owls. Wildl. Soc. Bull. 7:145-148. Otteni, L.C., E.G. Bolen and C. Cottam. 1972. Pre- dator-prey relationships and reproduction of the Barn Owl in southern Texas. Wilson Bull. 84:434-448. Weathers, W.W. 1972. Thermal panting in domestic pigeons, Columba livia, and the Barn Owl, Tyto alba J. Comp. Physiol. 79:79-84. . 1979. Climatic adaptation in avian standard metabolic rate. Oecologica (Berl.) 42:81-89. , . 1981. Physiological thermoregula- tion in heat-stressed birds: consequences of body size Physiol. Zool. 54:345-361. Wunder, B.A. 1979. Evaporative water loss from birds: effects of artificial radiation. Comp. Biochem Physiol. 63 A: 493-494. Dept, of Biology and the Ecology Center, UMC 53, Utah State Univ., Logan, UT 84322. Current Address: Dept, of Physiology and Biophysics, Univ. of Texas Medical Branch, Galveston, TX 77550. Received 18 December 1984; Accepted 20 March 1985 PEREGRINE FALCON SEMEN: A QUANTITATIVE AND QUALITATIVE EXAMINATION John Hoolihan and William Burnham Abstract — Collection frequencies and certain characteristics of Peregrine Falcon {Falco peregrinus) semen were investigated using semen from a falcon trained to copulate on a specially designed hat. Semen volume increased significantly when collections were increased from two to three times/day, but cells/ejaculate decreased. No significant difference in number cells/ ejaculate or cells/microliter was detected between morning and evening samples with two collections/day. Three collections/day resulted in decreasing total cell numbers/collections and numbers/microliter with the most cells collected during the initial morning collection. Semen showed a high motility, with estimated 80- 100% of sperm cells alive. The Peregrine Falcon {Falco peregrinus) conimnes, to be a focal point of captive propagation efforts (Cade and Dague 1981). An important technique used in captive propagation is artificial insemina- tion, since many captive falcon's do not copulate (Boyd 1978). The technique of artificial insemina- tion has been described by Boyd et al. (1977), but little attention has been directed toward quantita- tive or qualitative examination of falcon semen. We report here the affect of increasing frequency of semen collection upon semen volume and upon certain characteristics of peregrine semen, includ- ing concentration of sperm cells, total cells/ejacu- late, motility and percent of viable sperm cells. Materials and Methods We wished to know if daily semen volume could be increased significantly by collecting semen 3 times/d vs 2 times/d. Two periods were designated near the midpoint of the semen production cycle (Table 1). Period I com- prised 9 d when semen was collected 2 times/d, between 0800 H and 1015 H, and between 1715 H and 1745 H. A third collection was accomplished between 1300 H and 1345 H in Period II. Three days separated the two 9-day collection periods. All semen in this study was collected from a 10-year-old peregrine. The falcon was behaviorally imprinted to humans and copulated on a specially constructed hat (Cade and Dague 1981). The falcon was handled and raised as described by Boyd and Schwartz (1981). The falcon was given the opportunity to copulate on the hat only during the period when semen was needed for artifi- Table 1. Means (ranges in parentheses) of semen volume and sperm counts of a 10-year-old Peregrine Falcon. Time VoiVDay Cells//u,1 X 1 0^ Cells/Ejaculate x 10^ Period I 150 (116 - 185) 52.86 (38.12 - 81.12) 4.46 (2.55 - 5.84) (n=9) (n = 8) (n = 8) 0800- 1015 H 59.06 (45.62 - 81.12) 4.97 (3.51 - 5.84) (n=4) (n = 4) 1715 - 1745 H 46.66 (38.12 - 55.88) 3.95 (2,55 - 4.97) (n=4) (n=4) Period II 192 (175 - 208) 37.12 (26.25 - 60.62) 2.46 (1.27 - 3.88) (n = ll) (n = 15) (n = 15) 0800- 1015 H 47.54 (40.00 - 60.62) 3.32 (2.76 - 3.88) (n = 3) (n = 3) 1300 - 1345 H 36.47 (30.38 - 39.88) 2.61 (1.77 - 3.23) (n = 7) (n = 7) 1715 - 1745 H 31.78 (26.25 - 37.38) 1.72 (1.27 - 1.90) (n=5) (n=5) 125 Raptor Research 19 (4):125-127 126 Hoolihan and Burnham VoL. 19, No. 4 Figure 1. Semen production of a 10-year-old Peregrine Falcon. cial insemination. The semen was retrieved from the hat by use of blood capillary tubes. The capillary tubes were initially calibrated for volume by using a micropipette. Each millimeter (mm) of tube length represented 1 micro- liter (/U.1) of semen. Volume was therefore easily calcu- lated by measuring the length of semen in the tube with a metric rule. Concentration of spermatazoa per sample was calcu- lated by the use of a phase contrast hemocytometer. Sepa- rate means were calculated for the morning and evening collections since the collections were not evenly spaced over each 24 hr period. Standard poultry science methods for determining the percent of viable sperm were inadequate for peregrine semen quantification. Use of a live-dead stain was not helpful in determining fertilization capacity. The nigro- sin, eosin blue stain (Ernst 1970) which is intended to darken only dead cells, permeated both live and dead cells of the falcon semen. This technique needs to be perfected for falcons. Motility score of the semen was judged qualitatively. Samples were taken immediately to the laboratory once collected and mixed thoroughly in small vials pre-warmed to 37° C. Semen samples were then placed on pre-warmed slides which were kept at 37° C in a microscope stage incubator and viewed through a phase contrast micro- scope. Motility was judged qualitatively by the progressive motion and speed of the sperm cells, as well as the esti- mated percent of moving cells. Results and Discussion The 10-year-old male peregrine commenced copu- lation on 5 March and continued on a daily basis through 1 June when the opportunity to copulate was no longer made available to him, thus representing a semen production period of 95 d. Semen produced per copulation ranged from 0 (copulation, but no ejaculation) to 93 ml. Figure 1 compares the volume produced/ ejaculate with frequency of ejaculation for periods of both 2 and 3 collections/d. Semen volume rose significantly (28%, P < 0.001, Mann-Whitney U-test) when collections were increased from 2 to 3 times/d, but cells/ejaculate decreased significantly (P < 0.01) when collection frequency was increased (Table 1). During Period I, no significant difference (P = 0.20) in number of cells/jul or cells/ejaculate be- tween morning or evening samples was observed (Table 1). In contrast, in Period II a significant differ- ence (P < 0.025) existed in number of cells//al and cells/ejaculate between the 3 collection times. The mean number of cells//Ltl for the morning collection of Period II of 47.54 X 10^ shows a decrease of 19% compared Winter 1985 Peregrine Falcon Semen 127 with the same time in Period I (Table 1). The midday and evening collections for Period II had mean values of 36.47 X lO'"^ and 31.78 x 10^ cells//al, respectively, the latter showing a decrease for the evening collection times. Total sperm cells/ejaculate (in the morning col- lections of Period I) averaged 4.97 x 10^ (Table I), and evening collections averaged 3.95 x lO*' cells/ejaculate. Together, these figures represent a daily total average of 4.46 X 10® spermatazoa/ejaculate for Period I. In contrast, the mean for the morning, midday and even- ing collections of Period II were 3.32 x 10®, 2.61 x 10® and 1.72 x 10®, respectively (Table 1). We initially pre- sumed that Period II would show a decrease in spermatazoa/ejaculate and an overall daily total greater than Period I. However, fewer total cells were pro- duced in Period II. The semen collected showed a high motility value for more than 92% of the samples (n = 41) analyzed with an estimated 80 - 100% of the sperm cells alive and moving in a progressive motion. The speed with which the sperm cells move is difficult to evaluate with respect to their apparent fitness. It should be possible to correct this problem through the examination of samples from other captive and wild falcons. In this way, comparisons could be made and the normal speed could be ascer- tained. Semen from the peregrine tested fertilized eggs at a level equal to other donors of varying ages. Acknowledgments Tliis research was conducted at The Peregrine Fund’s Western Facility located near Fort Collins, Colorado. Financial support was provided by The Peregrine Fund, Inc. (T.J. Cade, President). Technical advice was supplied by R. Amen, Colorado State University Animal Reproduction Laboratory. D. Konkel, W. Heinrich and C. Sandfort trained the semen donor and performed most collections. J. Enderson and T. Cade re- viewed the manuscript and provided statistical assistance. Literature Cited Boyd, L.L., N.S. Boyd and F.C. Dobler. 1977. Repro- duction of prairie falcons by artificial insemination. /. WiUl Mgt. 4 1(2): 266-271. Boyd, L.L. 1978. Artificial insemination of falcons. Symp. Zool. Soc. London, No. 43, 73-80. Boyd, L.L, and C.H. Schwartz. 1981. Training im- printed semen donors. N. Am. Falconers’ Assoc. J. 20:65-69. Cade, T.J. and P.R. Dague. Eds. 1978. The Peregrine Fund Newsletter, No. 6, 12 pp. , Eds. 1981. The Peregrine Fund Newsletter, No. 9, 16 pp. Ernst, R.A. and F.X. Ogasawara. 1970. A live-dead stain to test poultry semen quality. Univ. of Calif. Ex- tension Service Bulletin OS A, No. 193. The University of Texas System Cancer Center, Science Park, Research Division, P.O. Box 389, Smithville, TX 78957. Address of Second author: The Peregrine Fund, World Center for Birds of Prey, 5666 West Flying Hawk Lane, Boise, ID 83709. First Received 1 April 1982; Accepted 22 April 1985 128 Douglas A. Boyce, Jr. VoL. 19, No. 4 Adult male Prairie Falcon and young at a typical Mojave Desert nest-site. Artwork by N. John Schmitt. PRAIRIE FALCON PREY IN THE MOJAVE DESERT, CALIFORNIA Douglas A. Boyce, Jr. Abstract — Twenty-five species of birds, 9 species of mammals, 5 species of reptiles and 1 species of insect were represented in prey remains and castings from 19 Prairie Falcon (Falco mexkanus) nests in the Mojave Desert, California, during 1977 and 1978. Reptiles represented a greater proportion in the diet than is reported in most other Prairie Falcon food studies in the western United States. The Horned Lark (Eremophila alpestris), Mourning Dove {Zenaidura macroura), Valley Pocket Gopher {Thomomys bottae) and Desert Woodrat {Neotoma lepida) were found in over 50% of the nests. Eighty-four percent of the prey weighed less than 1 50 g. The male Prairie Falcons. The Prairie Falcon {Falco mexicanus) is considered a generalist in prey selection (Bent 1938: Part 2). Mammals and birds are the most common prey taken, with specific prey frequencies varying re- gionally (Tyler 1923; Fowler 1931; Enderson 1964; Brown and Amadon 1968; Leedy 1972; Ogden 1973; Denton 1975; Haak 1982). Reptiles and in- sects are rarely recorded as prey (Table 1), although Snyder and Wiley (1976) reported an unusual re- liance on insects for food. T ypes of prey selection by Prairie Falcons nesting in the Mojave Desert con- trast sharply with prey previously recorded for this area. Pierce (1935) and Fowler (1935) reported a nest in the Mojave Desert where young Prairie Fal- cons were raised entirely on a diet of reptiles — mainly Chuckwalla {Sauromalus ohesus) and occa- mean prey weight was 107 gand equals 20% oftheweightof sionally Collared Lizard {Crotaphytus collaris), while Bond (1936) reported exclusively mammalian prey in 41 castings at another Mojave Desert nest. Be- cause little is known about food habits of Prairie Falcons in the Mojave Desert, I studied this aspect of their biology. Methods Prey remains and castings were collected from 19 falcon nests throughout the Mojave Desert (34° N 1 1 6° W) between March and June 1977 and 1978 in order to provide a qualitative summary of Prairie Falcon food habits. Prey remains and castings were also collected from immediately below the nest site when known to have come from no other raptor. Prey remains were identified in the field or compared with specimens at Humboldt State Univer- sity, Areata, California. Fresh weights for prey items were ob- tained from the Museum of Vertebrate Zoology, University of California, Berkeley, California. 1 used an adjusted weight Table 1. Frequency {%) of birds, mammals, reptiles and insect prey remains in Prairie Falcon nests in the western United States. Source LoCATiON Mammals Birds Reihiles Insects Fowler (1931) California 3QC 70 0 0 McKinley unpubl.^ Colorado 55 45 0 0 Marti and Braun (1975) Colorado 39 61 0 0 Ogden (1973) Idaho 53 33 14 trace S.R.B.P.b (1979) Idaho 22 72 6 0 Platt (1974) New Mexico 37 54 9 0 Voelker unpubl.^ Oklahoma 8 92 0 0 Porter and White (1973) Utah 8 92 0 0 Smith and Murphy (1973) Utah 31 50 0 19 This Study Mojave Desert 52 38 10 trace Mata from Sherrod (1978:96, 97) ^Snake River Birds of Prey annual report 1979 ‘'rounded to nearest 1 % 129 Raptor Research 19 (4):128-134 130 Douglas A, Boyce, Jr. VoL. 19, No. 4 of 500 g for rabbit species in Table 2 because, from the available information, it is unlikely Prairie Falcons are capable of carrying anything heavier (see discussion below). Quantifying prey remains and castings collected from hawk nests duringthe nestingseason is biased and unreliable (Errington 1932; Craighead and Craighead 1956). Some castings and prey remains may be deposited by falcons before nesting begins and persist until collection during the nesting season. Furthermore, Fowler (1931) reported that adult Prairie Falcons remove uneaten prey and castings from nests. Haak (1982) reported that a larger variety of prey was found at nests than was hunted, suggesting over-representation of uncommonly used prey at nests; however, observations of encounters with some prey species may be difficult to make. Prey remains may also underestimate the numbers of small rodents and birds actually captured (Cade 1960). Because of numerous potential biases, food habits reported here are qualita- tive not quantitative. Delineation of the Mojave Desert boundaries closely parallels the outer distributional limits of the Joshua Tree {Yucca brevifolia) (Jaeger 1957). Cresote {Larrea divaricata) and Burro Bush {Fanseria dumosa) are also characteristic desert flora. Alkali sinks, creosote bush scrub, shadscale scrub, Joshua Tree woodland, and Pinyon- Juniper woodland form the major Mojave Desert floral com- munities (Munz and Keck 1959). Table 2. Prey items identified at Prairie Falcon nests in the Mojave Desert. No.^ Estimated Species Nests Nests Weight (g) MAMMALS California Ground Squirrel {Spermophilus beecheyi) Mojave Ground Squirrel {Spermophilus mohavensis) Whitetail Antelope Squirrel {Ammospermophilus leucurus) Valley Pocket Gopher {Thomomys bottae) Pocket Mouse {Perognathus sp.) Kangaroo Rat {Dipodomy sp.) Deseret Woodrat {Neotoma lepida) Black-tailed Jack Rabbit {Lepus californicus) Desert Cottontail {Sylvilagus auduhonii) BIRDS Chukar {Alectoris chukar) Western Sandpiper* 3 15.8 500 {Calidris mauri) Rock Dove 1 5.3 27 [Columba livia) Mourning Dove 2 10.5 393 (Zenaida macroura) White-throateed Swift 8 42.1 109 {Aeronaut.es saxatalis) Western Kingbird 1 5.3 36 {Tyrannus verticalis) (Table 2 continued) 2 10.5 41 2 10.5 565 5 26.0 177 4 21.0 113 12 63.0 88 5 26.0 19 5 26.0 41 11 58.0 105 2 10.5 500 2 10.5 500 Winter 1985 Prairie Falcon Prey in California 131 (Continuation of Table 2) BIRDS (cont’d) Say’s Pheobe* {Sayornis saya) Horned Lark 1 5.3 25 {Eremophila alpestris) Cactus Wren* 12 63.2 28 {Campy lorhynchus brunneicapillus) Rock Wren 1 5.3 37 {Salpinctes obsoletus) 3 15.8 11 Sage Thraasher* {Oreoscoptes montanus) LeCont’s Thrasher* 1 5.3 44 (Toxostoma lacontei) Mountain Bluebird 1 5.3 62 {Sialia currucoides) 1 5.3 2.7 Loggerhead Shrike {Lanius ludovicianus) 1 5.3 45 European Starling (Sturnus vulgaris) Black-headed Grosbeak* 2 10.5 77 {Pheucticus melanocephalus) White-crowned Sparrow 3 15.8 46 {Zonotrichia leucophrys) Western Meadowlark 1 5.3 2 {Sturnella neglecta) 5 26.3 103 Red-winged Blackbird {Age lams phoeniceus) Brewer’s Blackbird 2 10.5 56 {Euphagus cyanocephalus) Scott’s Oriole* 3 15.8 58 {Icterus parisorum) Northern Oriole* 2 10.5 38 {Icterus galbula) 1 5.3 27 Western Tanager {Piranga ludoviciana) 4 21.1 31 House Sparrow {Passer dornesticus) House Finch 4 21.1 27 {Carpodacus mexicanus) 1 5.3 20 REPTILES Desert Iguana* {Dipsosaurus dorsalis) 1 5,3 56 Chuckwalla {Sauromalus obesus) 4 21.0 235 Zebra-tailed Lizard* {Callisaurus draconides) Desert Horned Lizard 1 5.3 2 (Phrynosoma platyrhinos) Western Whiptail 4 21.0 22 {Cnemidophorus tigris) 2 10.5 1 ^The number of nests in which a species was recorded. ^The number of nests in which a species was found divided by the number of nests examined (N = 19); times 100 and reported percentage. *Species not previously recorded in the literature as Prairie Falcon prey. 132 Douglas A. Boyce, Jr. VoL. 19, No. 4 Results and Discussion Thirty-nine species representing 3 vertebrate classes were present in prey collections from 19 nests (Table 2). Twenty-five species of birds, 9 species of mammals and 5 species of reptiles were identified. Insect parts were rarely noted and only 1 spiecies, Armored Stink Beetle {Eleodes armata) was identified. The Horned Lark, Valley Pocket Gopher and Desert Woodrat were present in over 50% of the nests. The Mourning Dove was present in 48% of the nests. Although the number of avian species captured outnumbered mammals by almost 3 to 1, the mean weight for birds (76 g) was half of the mean weight for mammals (179 g) suggesting greatest energetic return results from capturing mammals. Analysis of 214 pellets provides further evidence that mammals might be captured more often than birds or reptiles. Mammals were present in 72%, birds in 24% and reptiles in 4% of the pellets examined. In contrast to Pierce (1935) and Bond (1936) I found no instance where all or nearly all prey items were from just one vertebrate class. No single species appears as primary prey on a desert-wide basis (Table 2). Some species were infrequent in prey remains desert-wide but were locally frequent. For example, the Black-headed Grosbeak (Pheiic- ticus melanocephalus) was collected from 3 nests lo- cated along the east side of the Sierra Nevada Mountains but nowhere else in the desert. One nest had 8 grosbeaks present. Mammals. The Valley Pocket Gopher and De- sert Woodrat were found in over 50% of the nests. They were seldom seen except very early in the morning or late in the evening when temperatures were cooler. Their high abundance in the prey re- mains suggests that they were captured at these times. Harmataet al. (1978) found that Prairie Fal- cons forage primarily during early morning and late afternoon in the Mojave Desert. Blacktailed Jackrabbit {Lepus californicus) and De- sert Cottontail (Sylvilagus audubonii) feet were found in falcon nests. Adult Blacktailed Jackrabbit (2,590 g) and Desert Cottontail (1,700 g) weigh 3 to 5 times as much as adult male Prairie Falcons (554 g, Enderson 1964), making it unlikely that they car- ried them to their nests. It is probable that only very young rabbits or portions of them were carried to nests. Porter and White (1973) noted that Prairie Falcons prey on White-faced Ibis {Plegadis chihi, 519 g) in Utah. However, since White-faced Ibis were not found at Utah nests, they concluded that White-faced Ibis were too heavy for Prairie Falcons to carry. Adult Chukar {Alectoris chukar) and California Ground Squirrel {Spermophilus beecheyi) weigh between 500-565 g and were the next largest prey items found in eyrie samples and may have been brought to the nest by the female (863 g, Enderson 1964). Birds. The Horned Lark and Mourning Dove were found in 63 and 42% of the nests, respect- tively. The presence of a Western Sandpiper (Calidris mauri) (Table 2) demonstrates the oppor- tunistic hunting nature of Prairie Falcons. The Mojave River flows through the desert but is sub- terranean for much of its length. Sandpiper re- mains were found at a falcon nest 3.2 km from one of the few points where the river surfaces. The sandpiper was the only prey item not observed in the field. Reptiles. Most Prairie Falcon food studies show that reptiles are infrequently reported as prey (Table 1); however, reptiles did constitute a rela- tively high proportion of the prey in this study (9.5%). Desert Horned Lizard {Phrynosoma platyrhinos) and Chuckwalla were found at 20% of the nests. Reptile remains, however, were recorded in only 4% of the pellets. Reptile scales were found mixed with mammal hair in castings but no castings contained both scales and feathers. It seems likely most reptile scales are so thin that they are digested and not cast. Usually, the only indication that rep- tiles were being used was the presence of heads and tails found around the margin of the nest. Although only lizards were represented in prey remains I did observe a male falcon leave its perch on a power pole and capture a snake. The 20% Rule. Male falcons usually hunt for family groups during the nesting season (Newton 1979). Harmata et al. (1978) found that male Prairie Falcons hunted more frequently than females in the Mojave Desert. In this study 84% of prey cap- tured weighed less than 150 g and the mean weight was 107 g, or 20% of the weight of male Prairie Falcons. A mean prey weight 20% of mean adult male falcon weight is also common in other species of falcons. I noted a high correlation (r = 0.98) between mean prey weight during the breeding season and male falcon body weight for 5 species of falcons (Table 3). Because male falcons are re- stricted to a definite nesting territory during the breeding season, and are less restricted in move- ment during the remainder of the year, it seems Winter 1985 Prairie Falcon Prey in California 133 Table 3. Mean weight (g) of male falcons selected to show a weight range and the mean weight of their prey captured during the nesting season. Species Male Weight Prey Weight (X) Source Fako columbarius 187 26 Laing 1984 Falco eleonorae 350 62 Walter 1979 Fako mexicanus 554 143 This Study Fako peregrinus peaki 750 199 White 1973 Fako rusticolus 1,170 475 Roseneau 1972 probable that characteristics of prey vulnerability and density (during the breeding season) have evolutionarily dictated male falcon size. To test this hypothesis one needs to compare weight of prey captured by females when they begin to hunt after brooding is completed with that caught by males. An alternative hypothesis is that selection pressure is highest during winter months and not during the breeding season. If this were true male and female falcons should show significant differences in the weight of prey captured during winter. Acknowledgments This manuscript benefited from comments by J. Enderson, S. England, B. Haak, A. Harmata, J. Hodges, K. Kertell, D. Mindell, S. Platt, J. Sedinger and C. White. Anne Jacoberger, assistant curator for the Museum of Vertebrate Zoology, Berkeley, California and T. Lawler, Humboldt State University, Areata, California provided specimens. Bill Lehman and B. Hipp assisted in the field and J. Schmitt helped in identification of prey remains. Lhe study was supported partially by the U.S. Bureau of Land Management and U.S. Fish and Wildlife Service. Literature Cited Bent, A.C. 1938. Life histories of North American birds of prey. Part 2. U.S. Natl. Mus. Bull. 167. Dover Publi- cations, New York. Bond, R.M. 1936. Some observations on the food of the Prairie Falcon. Condor 38:169-170. Brown, L.H. and D. Amadon. 1968. Eagles, hawks and falcons of the world. McGraw-Hill, New York, NY. Cade, T.J . 1 960. Ecology of the peregrine and gyrfalcon in Alaska. Univ. of Calif. Publ. Zool. 63:151-290. Craighead, J.J. and F.C. Craighead, Jr. 1956. Hawks, owls and wildlife. The Stackpole Co., Harrisburg, PA., and Wildl. Manag. Inst., Washington, D.C. Denton, S.J. 1975. Status of the prairie falcons breeding in Oregon. M.S. thesis, Oregon State Univ., Oregon. 56 pp. Enderson, J.H. 1964. A study of the prairie falcon in the central Rocky Mountain region. AmA 81:332-352. Errington, P.L. 1932. Technique of raptor food habits study. Condor 34:75-86. Fowler, F.H. 1931. Studies of food and growth of the Prairie Falcon. Condor 33:193-201. . 1935. Week-ends with the Prairie Fal- con. NaL Geog. Mag. 67:610-626. Haak, B. A. 1982. Foragingecology of Prairie Falcons in northern California. Unpubl. M.S. Thesis, Oregon State University, 64 pp. Harmata, A.R., J.E. Durr and H. Geduldig. 1978. Home range, activity patterns and habitat use of Prairie Falcons nesting in the Mojave Desert. Unpubl report U.S. Bureau of Land Management contract No YA-512-CT8-43. 89 pp. Laing, K. 1985. Food habits and breeding biology of merlins in Denali National Park, Alaska. Raptor Res. 19(2/3):42-51. Leedy, R.R. 1972. The status of the Prairie Falcon in western Montana: Special emphasis on possible ef- fects of chlorinated hydrocarbon insecticides. M.S. Thesis, Univ. of Montana. 96 pp. Marti, C.P., and C.E. Braun. 1975. Use of tundra habitats by Prairie Falcons in Colorado. Condor :21S- 214. Newton, I. 1979. Population ecology of raptors. Buteo Books, Vermillion, South Dakota. Ogden, V.T. 1973. Nesting density and reproductive success of the Prairie Falcon in southwestern Idaho M.S. thesis, Univ. Idaho. 43 pp. Pierce, W.M. 1935. Experiences with Prairie Falcons Condor 37:225. Platt, S.W. 1974. Breeding status and distribution of the Prairie Falcon in northern New Mexico. Unpubl. Manus. 68 pp. Porter, R.D. and C.M. White. 1973. The Peregrine Falcon in Utah, emphasizing ecology and competition with the Prairie Falcon. Brigham Young Univ. Sci. Bull., Bio. Ser. 18:1-74. Roseneau, D.G. 1972. Summer distribution, numbers 134 Douglas A. Boyce, Jr. VoL. 19, No. 4 and food habits of the Gyrfalcon (Falco rusticolus) on the Seward Peninsula, Alaska. Unpubl. M.S. thesis, Univ. Alaska. 124 pp. Sherrod, S.K. 1978. Diets of North American Fal- coniformes. Raptor Research 12:49-121. Smith, D.G. AND J.R. Murphy. 1973. Breeding ecology of raptors in the eastern Great Basin of Utah. Brigham Young Univ. Sci. Bull., Bio Ser. 28:1-76. Snyder, N.F.R. and J.W. Wiley. 1976. Sexual size di- morphism in hawks and owls of North America. A.O.U. Ornithological Monographs 20:1-96. Tyler, J.G. 1923. Observations on the habits of the Prairie Falcon. Condor 25:90-97. U.S. Dept. OF Interior. 1979. Snake River Birds of Prey Research Project Annual Report. U.S. Bureau of Land Management, Boise District, Boise, Idaho. VoELKER, W.G. 1978. Food habits data for Ferruginous Hawk, Red-tailed Hawk, Swainson’s Hawk, Broad- winged Hawk, Golden Eagle and Prairie Falcons. Un- publ. manuscript. In: Sherrod, S.K. 1978. Diets of North American Falconiformes. Raptor Research 12:49-121. Walter, H. 1979. Eleonora’s Falcon. Univ. of Chicago Press, Chicago, 111. White, C.M., W.B. Emison and F.S.L. William- son. 1973. DDE in a resident Aleutian Island pere- grine population. Condor 75:306-311. Zoology Dept., Brigham Yoimg University, Provo, Utah 84602. Received 15 March 1985; Accepted 1 June 1985 PERCHING AND ROOSTING PATTERNS OF RAPTORS ON POWER TRANSMISSION TOWERS IN SOUTHEAST IDAHO AND SOUTHWEST WYOMING John C. Smith Abstract — As part of an ongoing raptor management program, 45 km of 345 kilovolt (kv) transmission lines were surveyed from 5 June to 31 September 1983 to determine diurnal and nocturnal raptor use patterns. The Golden Eagle {Aquila chrysaetos) and Red-tailed Hawk {Buteo jamaicensis) perched mostly on upper, outer sections of transmission towers during the day and roosted on lower, inner sections at night. Daytime surveys alone may not accurately represent raptor use of these structures. In many treeless areas where availability of nest, perch and roost sites may limit raptor populations, electrical powerline structures are readily utilized by many raptor species (Stahlecker 1979; Olen- dorff et al. 1981). In recent years utility companies have become more aware that the raptor/ powerline association is sometimes detrimental to both man and bird, and have initiated studies to examine raptor use of powerlines. The most commonly used technique is daytime aerial surveying (e.g., Wilder 1981; Hansen 1982). Relatively little information has been gathered concerning raptor roosting be- havior on powerlines and how it may compare to perching behavior (Craig and Craig 1984). This paper presents results of a study funded by Idaho Power Company in spring and summer of 1983 (Smith 1983), which was designed to collect infor- mation on nocturnal and diurnal behavior of rap- tors on electrical transmission towers in southeast Idaho and southwest Wyoming. Study Area and Methods The study area is located 30 km north of the convergence of the Idaho/Wyoming/Utah borders (Fig. 1). Three 345 kv transmission lines transmit electrical power through the study area from a coal-fired generating plant near Rock Springs, Wyoming to 3 separate substations bordering the Snake River plain in southern Idaho. The 45 km study section is situated on the Idaho/Wyoming border and traverses mostly rolling, arid, treeless terrain 1800-2100 m in Figure 1. Transmission line route and study area. 135 Raptor Research 19(4):135-138 136 John C. Smith VoL. 19, No. 4 |« 10m H FRONT VIEW SIDE VIEW Figure 2. Configuration of 345kv transmission tower. elevation. Three lines in the study area contain a total of 348 guyed aluminum towers, 25-32 m b height (Fig. 2). Dommant plant species for most of the area is big sagebrush (Artemesia tridentcUa). Raptors most commonly sighted on towers were the Red-tailed Hawk {Bvteo jamaicensis) and Golden Eagle (Aqidla chrysaetos). During the post-fledgmg period (10 July to 31 September), an observed maximum of 28 fledglmg and adult Red-tailed Hawks and 8 fledglmg and adult Golden Eagles used the towers b this area for roost and/or perch sites. Seven Red-tailed Hawk nests and 2 Golden Eagle nests were the only occupied raptor nests present on transmission towers withm the study area b 1983. The study area was surveyed from a vehicle on 45 nights be- tween 5 June and 31 September 1983. Surveys began at dusk and usually termbated 1-2 h before dawn. Each tower was exambed usmg a hand-held spotlight and bboculars. The reflective property of the raptors’ retbae aided b locatbg birds at night. A light amplification device, or nightscope, was found to be unsuitable for this task due to badequate magnification when used alone and poor resolution when used b conjunction with bboculars or spottbg scope. Observatbns of birds at specific roost sites were made on 24 nights between 24 June and 9 September, to determbe if movement to and from roost sites took place during the night. In all cases. Golden Eagles (n = 19 nights at 14 locations) and Red-tailed Hawks (N=5 nights at 5 locations) did not move from their roost towers at any time during the night. Lines were also surveyed from the ground on 15 d between 21 July and 31 September. Day surveys began at 0700 H and were completed by 1400 H. Perching/roosting observations were classified according to time of day, species, and position on tower. “Inside” refers to any position on the tower that is surrounded on at least 4 sides by tower members (referring to the 6 sides of a cube). Upper/lower position designation used in data analysis (fig. 2) was chosen because very little perching/ roosting occurred in the slanted portions of the towers (Red-tailed Hawks — less than 10% of all observations, Golden Eagles — zero observations). Birds were observed perched mably b 2 regions of the transmission towers, the uppermost horizontal crossbridge area and the lower horizontal crossarm area (Eig. 2). Results and Discussion Most significant observed differences between diurnal and nocturnal use patterns were as follows: 1. Eagles and hawks showed a significant shift from using outer tower sections during the day to using inner tower sections at night. 2. Both species exhibited a shift from using upper sections of the towers during the day to using lower sections at night. Data for Red-tailed Hawks consisted of 99 perch and 236 roost observations. Data for Golden Eagles consisted of 46 perch and 124 roost observations. Erequencies of observations in each category were used to generate 2x2 chi-square contingency tables to test the null hypothesis that time of day was independent of observed perch/roost location on the towers. Chi-square values (Eig. 3) indicate that Winter 1985 Raptors and Power Transmission Towers 137 X^=100.6 (p<.001) 124.2 (p<.001) n=l70 n=170 X"=27.4 (p<.001) X'' = 13.9 (p<.001) Figure 3. Relative frequencies of perch and roost observations on transmission towers in southeast Idaho and southwest Wyoming for the period 5 June to 31 September 1983. Chi-square (x^) values were generated from observed frequencies in each category. Day = 0700-1959 H. Night = 2000-0659 H. diurnal use patterns differed significantly from nocturnal use patterns for both species. Results in- dicate that daytime surveys alone may not accu- rately represent overall use of towers as perch/roost structures, and should be supplemented by noctur- nal observations. Red-tailed Hawks exhibited larger day-outside/ night-inside differences than did Golden Eagles 90% of red-tail sightings were of birds in immature plumage. Adult red-tail sightings were con- fined to small meadows and clear-cuts surrounding the main flats, Adults may have limited themselves to peripheral areas to avoid harassment from immatures who often congregated around kills. Once we observed up to 11 immature red-tails fighting over a single prey. The Ferruginous Hawk (Buteo regalis) was the next most fre- quently sighted raptor, averaging 31.4 birds/survey (Table 1) with a range of 7 - 67. Most Ferruginous Hawks sighted were also in immature plumage. Except for 2 birds perched on the edge of a clear-cut in 1983, all Ferruginous Hawks were sighted on the main flats. The observation bluff was a particularly good concentration spot, with less vegetation, allowing excellent views from ground level. Ferruginous Hawks have been known to move to Henrys Lake Flats from the Raft River Valley along the Utah-Idaho border, about 250 km to the southeast (Thurow et al. 1980. Raptor Ecol- ogy of Raft River Valley, Idaho, E.G. and G., Inc., Idaho Falls, Idaho, and pers. obs.). In late summer food availability becomes limited in Raft River Valley since Black-tailed Jackrabbits (Lepus califomicus) become less diurnal to avoid heat (Thurow et al. 1 980). The Ferruginous Hawks apparently respond by drifting on pre- vailing wind currents, which move primarily towards the Henrys Lake area. The Swainson’s Hawk (Buteo mainsoni) sightings averaged 13.2 birds/survey for the 10-yr period (Table 1) with a peak of 34 in 1980. Unidentified buteos and 9 other diurnal raptors sighted accounted for an average of 23.9 more sightings/survey. The heavy concentration of raptors at Henrys Lake Flats is probably due to the abundance of Richardson’s Ground Squirrels (Spermophilus richardsoni) . Ground squirrels at lower elevations are known to estivate in late summer and fall, when hot, dry weather eliminates or drastically reduces succulent vegetation (Ingles, L.G. 1965. Mammals of the Pacific States. Stanford University Press, California). The high elevation of Henrys Lake Flats keeps vege- tation green, and the ground squirrels are active and available as prey. There may be a general tendency for raptors to move up- slope as ground squirrels estivate and rabbits become more noc- turnal. We have observed similar concentrations of buteos in early fall from 2,000 to 3,000 m elevation on Steens Mountain in south- east Oregon, where Belding’s Ground Squirrels (Spermophilus bel- dingi) were still active. In addition to an abundant food supply, the Henrys Lake area lies just west of the Continental Divide and may act as a corridor for migrating birds in general (Larrison, E. 1981. Birds of the Pacific Northwest: Washington, Oregon, Idaho and British Columbia. University Press of Idaho, Moscow). Our automobile surveys indicate that high mountain meadows are important late summer concentration areas for buteos, especially those in immature plumage. The Henrys Lake Flats and other high meadows of the intermountain west have become increasingly popular recreation areas. Recreation and other forms of land use may affect high meadow ground squirrel populations, which in turn may affect raptor concentrations in those areas. Acknowledgments M. DeLate, T. Reynolds, M. Reynolds, S. Trost and C. Webb helped to conduct surveys. Earlier drafts of this paper were im- proved by comments from M. Collopy and J. Gessaman. Department of Biology, Idaho State University, Pocatello, Idaho 83209. Received 6 March 1984; Accepted 22 April 1985 Winter 1985 Short Communications 145 Bald Eagle {Haliaeetus leucocephalns) Consumption of Harbor Seal {Phoca vitulina) Placenta in Glacier Bay, Alaska John Calambokidis and Gretchen H. Steiger This note reports on the frequent consumption of Harbor Seal {Phoca vitulina) placenta by the Bald Eagle {Haliaeetus leucocephalus) and a fluctuation in numbers of Bald Eagles in Muir Inlet, Alaska, in relation to the availability of this food source. From 30 May to 23 August 1982 and 8 to 13 June 1984, we spent 41 d in our study area in the northern portion of Muir Inlet, located in the northeast corner of Glacier Bay in southeast Alaska. This recently (within the last 20 yr) deglaciated area is about 20 km long and an average of 2 km wide. The shoreline rises steeply on both sides of the inlet and consists of loose rock and glacial debris. There are no trees and vegetation is extremely sparse. Up to 1 ,000 Harbor Seals rest and give birth to youngon small icebergs formed by an active tidewater glacier at the head of Muir Inlet. Our research was focused on the biology and behavior of Harbor Seals m this area. Our regular censuses and observations of seals re- quired us to scan the entire inlet with binoculars and spotting scopes and consequently observe eagles and their interactions with seals. On 9 occasions in early June, we observed Bald Eagles feeding on Harbor Seal placenta; these were the only times we saw eagles feeding in our study area. In one instance we saw 6 eagles either feeding on the placenta, chasing after an eagle with placenta, or perching near a feeding eagle. At each of 3 Bald Eagle perches visited inearlyjune 1982, we found from 2 to 15 clumps of lanugo hair (the fetal coat of Harbor Seal pups that is shed before birth and is expelled with the placenta). Bald Eagle numbers in our study area changed through the season and corresponded to the time of Harbor Seal pupping. We saw a minimum of 4-7 eagles on 5 d between 31 May to 17 June 1982 and a minimum of 5 on 2 d between 8 and 13 June 1984. We saw fewer eagles during visits later in the season. During the latter part of June we saw up to 2 eagles. In 16 d of observation in July and August 1982, we had only one eagle sighting. Bald Eagles in Muir Inlet consisted about equally of mature and immature birds, 4 of the 7 seen at one time in June 1982 and 3 of the 5 seen at one time in June 1984 were mature. The majority of Harbor Seal pups m Muir Inlet are born in late May and early June, the same period we saw the largest numbers of Bald Eagles. In both 1982 and 1984, over 300 Harbor Seal pups were born in this portion of Muir Inlet. Given a minimum weight of 1 kg for a Harbor Seal placenta, this would mean an excess of 300 kg of food available to eagles. We concluded that Bald Eagles in this area during late May and early June subsist largely or entirely on placenta of Harbor Seals because: 1) our frequent observations of eagles feeding on placenta and not on other food, 2) the abundance of this food source and the scarcity of other food sources in this deglaciated area, 3) the presence of seal lanugo hair found at eagle perches, and 4) the close parallel between the number of eagles in our study area and the Harbor Seal pupping season. Eagles appear to use this area for only a short period; we found no evidence of eagle nesting. Sherrod et al. (Living Bird 15:143-182, 1976) reported that Bald Eagles on Amchitka Island, Alaska consume northern Sea Lion {Emetopias jubatus) afterbirth. It is the only other report we know that mentions Bald Eagles feeding on placenta of pinnipeds. We have observed Bald Eagles feeding on seal placenta and scavenging on dead seal pups in other parts of Glacier Bay and Puget Sound, Washington. Acknowledgments Funding was by the School for Field Studies, Cambridge, MA. The National Park Service provided permits and Gary VeQuist was instrumental in this regard. Staff and students with the School for Field Studies aided in data collection. Sue Carter and Robin Butler made additional contributions. Al Harmata and Jon Ger- rard critically reviewed the manuscript. Cascadia Research Collective, Waterstreet Bldg., Suite 201, 218>/2 W. 4th Ave., Olympia, WA 98501, Received 22 January 1985; Accepted 1 May 1985 Barred Owl Hunting Insects Arnold Devine, Dwight G. Smith and Mark Szantyr Although the Barred Owl {Strix varia) is partially insectivorous (Bent, U.S. Natl. Mus. Bull. 170, 1938) its methods of hunting and capturing insects have not been described. From 1924-2000 H we observed a Barred Owl hunting insects on 4 April 1984 at Blue Springs Stake Park, Orange City, Florida. The Barred Owl was apparently hunting noctuid moths (Lepidoptera) and large vein- winged insects on the lawn of an historic house in the park. The owl hunted these insects from a small stump or on a sandy stretch of lawn beneath a lighted area. In hunting, the owl sat motionless except for slight head movements to watch the insects. Captures were attempted only after the insects landed. Capture attempts were a combination of 3 movements; 1) a bound initiated from a partially forward leaning position, 2) a single wing flap and 3) a short glide. Attempts covered 1-2 m di.stances and the owl was twice observed to follow mfssed attempts with 2 or 3 immediate additional pounces. Insects were captured with the talons and consumed by bringing the head down to pick the insect from the talons. One insect not immediately consumed was transferred to the beak before the owl flew to a nearby tree. At 1 949 H the Barred Owl returned to its hunting perch on the lawn where it unsuccess- fully attempted two more captures before leaving the area at 2000 H. During the time observed, the Barred Owl was successful in 2 of 18 capture attempts. Forsman et al., (Wildl. Mongr 87, 1984) reported that the Spot- ted Owl {Strix occidentalis) diet also includes insects and that these owls used pounces to capture insects on the ground or on tree limbs. Also, mid-air captures of flying insects were not observed. Biology Department, Southern Connecticut State University, New Haven, CT 06515. Received 22 March, 1985; Accepted 20 May 1985 146 Short Communications VoL. 19, No. 4 Northern Harrier Predation on Greater Prairie Chickens in Southwest Missouri Brian Toland Although habitat preferences of the Northern Harrier (Circus cyaneus) and the Greater Prairie Chicken (Tympanuchus cupido) are quite similar (Berger et al. 1963), harriers are rarely reported to prey upon these galliformes (Yeatter 1943; Schwartz 1945; Grange 1948; Weller et al. 1955; Ammann 1957; Berger et al. 1963). Other similar-sized avian prey such as Ring-necked Pheas- ant (Phasianus colchicus), Sharp-tailed Grouse (T. phasianellus), American Bittern (Botaurus lentiginosus), ducks and the Domestic Chicken (Gallus spp.) are, however, not infrequently taken (Fisher 1893; Peabody 1900; Errington and Breckenridge 1936; Bent 1937; Brown and Amadon 1968) although usually as juveniles (Peabody cit.; Saunders 1913;Randall 1940; Hecht 1951). This note reports harrier predation on adult and young Greater Prairie Chickens in the tail-grass prairie region of southwest Mis- souri during spring and summer 1984. The study area of 850 ha consisted of Prairie State Park and surrounding private lands. Prairie State Park is 1 mi southwest of Liberal, Missouri, in Barton County. Vegetation consists of bluestem grasses (Andropogon spp.), Indian grass (Sorghastrum nutans) and other native grasses and forbs, as well as invading cool season grasses such as fescue (Festuca sp.). Old and reclaimed strip mines and deciduous woody growth are scattered throughout the area. Neighboring lands are mostly crops and fescue (Larson 1982). A total of 325 h were spent observing harriers and prairie chickens from 7 April - 7 August 1984. Using techniques de- scribed by Hamerstrom (1969), I found 7 harrier nests (density of Tpair/121 ha) clumped in 3 loose aggregations in undisturbed grasslands. Approximately 150 prairie chickens were concentrated around 4 booming grounds on the study area during early spring (April-May) and later scattered throughout the area during nest- ing (May-July). At least 2 prairie chicken nests were located within 200 m of 2 harrier nests. Visits to Northern Harrier nests during the nestling stage were made to collect prey remains and/or pellets. 1 calculated frequency of occurrence of prey types from fresh pellets and identified prey remains. Percent composition of each prey species was calculated from the number of each type divided by the total. Percent biomass was estimated by weights given in Schwartz and Schwartz (1959), Terres (1980) and Steenhof (1983). Analysis of food items revealed a catholic diet (Table 1). The diet of nesting Northern Harriers in other regions has been of a similar euryphagus composition (Randal op. cit.-, Hecht op. cit , Craighead and Craighead 1956; Brown and Amadon 1968; Smith Table 1. Prey of nesting Northern Harriers at Prairie State Park in southwest Missouri, 1984. Frequency Average OF % WEIGHT (g) Estimated Prey OCCURRENCE COMPOSITION % BIOMASS BIRDS Greater Prairie Chicken (Tympanuchus cupido) 8 6.6 624 22.6 Adults 3 908 12.3 Juveniles 5 454 10.3 Mourning Dove (Zenaida macroura) 3 2.5 134 1.8 Eastern Meadowlark (Sturnella magna) 6 4.9 95 2.6 Common Crackle (Quiscalus quiscala) 2 1.6 112 1.0 Red-winged Blackbird (Agelaius phoeniceus) 6 4.9 50 1.4 Brown-headed Cowbird (Molothrus ater) 3 2.5 41 0.5 Unidentified passerines 11 9.0 75 3.7 Total birds 39 32.0 33.6 (Table 1 continued) Winter 1985 Short Communications 147 (Continuation of Table 1) MAMMALS Prairie vole {Microtus ochrogaster) 24 20.0 8 4.1 Fulvous harvest mouse {Reithrodontomys fulvescens ) 6 4.9 21 0.5 Deer Mouse {Peromyscus maniculatus) 2 1.6 20 0.2 Cotton rat {Sigmodon hispidus) 1 0.8 120 0.5 Eastern wood rat (Neotoma floridana) 1 0.8 255 1.2 Unidentified rodents 7 5.8 30 0.9 Eastern cottontail {Sylvilagus floridanus) 9 7.4 1200 49.0 Total mammals 50 41.3 56.4 REPTILES Plains garter snake {Thamnophis radix) 1 0.8 109 0.5 Unidentified snakes 11 9.1 190 9.5 Total reptiles 12 9.9 10.0 INSECTS Coleopterans 12 9.9 0.5 tr‘ Orthopterans 8 6.6 1 tr Total insects 20 16.5 tr TOTAL PREY ITEMS 121 100.0 100.0 Hr = trace. and Murphy 1973; Snyder and Wiley 1976). A total of 7 prairie chicken remains were collected from the 2 harrier nests closest to prairie chicken nests. Of these 7 remains, 5 represented half- grown juveniles and 2 represented adults. An eighth prairie chicken was captured by an adult female harrier on 25 July at 0700 H. The hawk hovered briefly 4 m above a dense stand of bluestem grasses and fescue, before diving into the vegetation. After waiting about 10 min, I approached the site and the hawk flushed when I was about 20 m away. I discovered a dead adult female prairie chicken that was partly deplumed and still warm. 1 was unable to find a prairie chicken nest in the immediate vicinity, but numerous droppings and matted vegeta- tion (form) indicated that the prairie chicken had been on its roost. 1 left the site and watched from a distance of ca 300 m until the harrier returned to her kill after nearly 20 min. Berger et al. (1963) observed prairie chickens being captured by raptors (in- cluding 1 female Northern Harrier) early in the morning. Campbell (1950) reported an unsuccessful capture attempt of a Lesser Prairie Chicken (T. paUidicinctus) during evening hours. Poor light during early morning and late evening hours may make approaching raptors more difficult for prairie chickens (or other quarry) to spot (Berger et al. 1963). All prairie chicken prey was brought to harrier nests during the last half of the nestling stage. During this time female harriers spent as much time hunting for their young as did males. It is probable that the larger females (50% heavier than adult males) caught the adult prairie chickens (Berger et al. 1963). I observed several adult male harriers feeding on mammalian prey among 148 Short Communications VoL. 19, No 4 displaying prairie chickens at booming grounds just prior to the nesting season. The prairie chickens seemed oblivious of these male harriers. Female harriers, however, usually evoked a re- sponse from prairie chickens, ranging from a brief squat to an all out flush. Berger et al. (1963) reported that over a 4-year sample of harrier-prairie chicken reactions, prairie chickens flushed nearly 70% of the times female harriers approached, but only 30% of the times males approached. Of the 33 times that prairie chick- ens completely ignored approaching harriers, 94% were male hawks and 6% were females. Female Hen Harriers (C. c. cyaneus) take significantly more Red Grouse {Lagopus lagopus) and other gamebirds than do males (Marquiss 1980). I have found no evidence of Northern Harriers preying on Greater Prairie Chickens during winter or on booming grounds in early spring. However, prairie chickens did comprise a significant proportion of Northern Harrier diets (22.6% biomass; Table 1) during the nesting season when female and juvenile prairie chick- ens in close proximity to harrier nests may be more vulnerable to raptor predation. Acknowledgments Toney Chiles contributed invaluable field assistance. The Mis- souri Department of Natural Resources provided funding and technical assistance for this study through a state park research grant. Nancy Thompson-Toland helped with expenses and field work. Keith Bildstein, Clayton White and an anonymous referee made editorial suggestions which improved the manuscript. Literature Cited Ammann, G.A. 1957. The prairie grouse of Michigan. Michigan Dept. Conserv. Tech. Bull. 200 pp. Berger, D.D., F. Hamerstrom and F.N. Hamer- STROM. 1963. The effect of raptors on prairie chic- kens on booming grounds./. Wildl. Manag. 27:778- 791. Bent, A. C. 1937. Life histories of North American birds of prey (order Falconiformes). Part 1. U.S. Natl. Mus. Bull. 167. Dover Publ., New York. Brown, L.H. and D. Amadon. 1968. Eagles, hawks and falcons of the world. McGraw-Hill, New York. Campbell, H. 1950. Note on the behavior of Marsh Hawks toward Lesser Prairie Chickens. J. Wildl. Manag. 14:477-478. Craighead, J.J. and F.C. Craighead, Jr. 1956. Hawks, owls and wildlife. Stackpole Co., Harrisburg, PA. Errington, P.L. and W.J. Breckenridge. 1936. Food habits of Marsh Hawks in the glaciated prairie region of north-central United States. Am. Midi. Nat. 7:831- 848. Fisher, A.K. 1893. The hawks and owls of the United States and their relation to agriculture. U.S. Dept. Agr. Bull. 3, Washington, D.C. Grange, W.B. 1948. Wisconsin grouse problems. Wis- consin Conserv. Dept. 318 pp. Hamerstrom, F. 1969. A harrier population study. Pages 367-383. In J.J. Hickey (Ed.), Peregrine Falcon populations: their biology and decline. Univ. Wiscon- sin Press, Madison. Hecht, W.R. 1951. Nesting of the Marsh Hawk at Delta, Manitoba. Wilson Bull. 63:167-175. Larson, L. 1982. Prairie State Park: an introduction to one of Missouri’s public prairies. Missouri Prairie J. 3:4-11. Marquiss, M. 1980. Habitat and diet of male and female Hen Harriers in Scotland in winter. British Birds 73:555-560. Peabody, P.B. 1900. How a Marsh Hawk grows. Bird Lore 2:43-49. Randall, P.E. 1940. Seasonal food habits of the Marsh Hawk in Pennsylvania. Wilson Bull. 52:165-172. Saunders, A. A. 1913. A study of the nesting of the Marsh Hawk. Condor 15:99-104. Schwartz, C.W. 1945. The ecology of the prairie chicken in Missouri. Univ. Missouri Studies 20: 1-99. AND E.R. Schwartz. 1959. The wild mammals of Missouri. Univ. Missouri Press and Mis- souri Dept. Conserv. Smith, D.G. and J.R. Murphy. 1973. Breeding ecology of raptors in the eastern Great Basin of Utah. Brigham Young Univ. Sci. Bull., Biol. Ser., Vol. 28(3). Snyder, N.F.R, and J.W. Wiley. 1976. Sexual size di- morphism in hawks and owls of North America. AOU Monogr. 20. Steenhof, K. 1983. Prey weights for computing percent biomass in raptor diets. Raptor Res. 1 7 : 15-27. Terres, J.K. 1980. The Audubon Soc. encyclopedia of North American birds. Alfred A. Knoopf, Inc., New York. Weller, M.W., I.C. Adams, Jr. and B.J. Rose. 1955. Winter roosts of Marsh Hawks and Short-eared Owls in central Missouri. Wilson Bull. 67:189-192. Yeatter, R.E. 1943. The prairie chicken in Illinois. //- linois Nat. Hist. Surv. Bull. 22:377-416. Missouri Department of Natural Resources, Natural History Program, P.O. Box 176, Jefferson City, MO 65102. Current address: Route 4, Box 165, Columbia, MO 65201. Received 8 April 1985; Accepted 15 July 1985. Winter 1985 News and Reviews 149 The Migration of Birds of Prey in the Northern Red Sea Area: Report of the 1982 Suez Study by David Wimpfheimer, Bertel Bruun, Sherif M. Bahael Din and Michael C. Jennings with contributions by William S. Clark, Carstenjensen, Donald Parr and Ib Petersen, and forward by Dean Amadon. Arabic summary by Assad Serhal. 80 pp., 6 Tables, 24 Figures, 2 Appendices, 10 plates. Available from the Holy Land Conservation Fund, 1825 Eye Street Northwest, Suite 400, Washington, DC 20006. $20.00 U.S. Whenever the nation of Egypt is mentioned, thoughts come to mind of the pharaohs, the great pyramids and the sphinx. One also remembers Egypt’s biblical and more recent history, both closely tied to the nation of Israel. Thoughts of migrating raptors do not immediately come to mind. Yet this report has made it apparent that a spring migration of raptors does occur over the lands of Egypt, and undoubtedly has done so since before the great pyramids were built. The report describes the initial results of the Holy Land Con- servation Fund’s expedition to Suez, Egypt, in the springof 1982. As a result of many individual efforts and outstanding support from numerous individuals and agencies, both in the United States and Egypt, the authors have provided students of raptor migration with a data base for reference and future comparison for the Middle East. All of the authors except one have previous experience with Eurasian raptors. Observational data are re- ported for 124,996 raptors, representing 28 species, sighted dur- ing the period 23 February - 16 May 1982. The primary goal of the study was to learn more about the spring migration of raptors at or near Suez, Egypt, and towards that goal the authors have a good start. However, there is some question as to whether the report effectively establishes the Suez area as a concentration point as stated. Certainly there is a substantial spring overfly in the region, but the evidence supports the idea that raptors do not initiate migrations in the immediate vicinity of the city of Suez, and thus do not concentrate themselves in the area. A species by species account of sightings by time period and a seasonal total is provided for each of the 28 species tallied. Com- parisons by species are made with other regions, particularly Eliat, Israel. Six species, Buteo b. vulpinus, Aquila nipalerisis. A pomarina, Mtlvus migrans, Circaetus gallkus and Neophron percnopterus ac- counted for 90% of total sightings. Sightings oiB.b. vulpinus alone accounted for almost 65% of total numbers, hut the vulpinus tally is biased by the inclusion of all B. buteo sightings with the vulpinus totals, as pointed out by the authors. Less than 10 individuals were tallied for 12 species. Observational data for 214 non-raptors are provided in Appendix A, which includes 3 new sightings for Egypt. Histograms of related species are provided depicting total numbers versus date. The Figures could have been combined in many cases, especially Figures 14 and 15 and Figures 17 and 18. Analysis by 5-day interval would have been most helpful and welcome, but such was provided only for accipiters, which rep- resented 0.2% of total sightings. At least 2 observers were present on most days, and there was a gap in continuous coverage during early April when no observa- tions were made. In order to compensate for these gaps, the authors extrapolated data for observations both before and after periods of no coverage. On this basis, adjustments were calculated for selected species, including Aquila sp., A. pomarina and A. mpaknsis. Adjustments were made with the assumption that the proportions of identified A^iuTa is the same as unidentified, which is confusing. However, these adjustment figures do not appear in final tallies and conclusions. Virtually every individual raptor sighted was identified at least to genus, and no “unidentified” category appears in the final tallies. As one who has observed North American migrations over the years, it is simply not possible to always pinpoint an individual, though worthy a goal such iden- tification may represent. Intermittent observations made in areas adjacent to Suez were also accomplished. Brief summaries are provided for Hurghada and surrounding area, for northern Sinai between El Arish and Nakhl, for Ismalia north of Suez (all observations accomplished by one or more of the authors), and summaries of previous reports in the literature for the region and for Eliat, Israel. Previous reports and more recent studies indicate the migration at Eliat is substan- tially greater than reported for Suez and surrounding areas (W.S. Clark, pers. comm.). Also included is a chapter on raptor migra- tion in the Middle East which provides the reader with a nice comparison as well as a substantial reference list. As the authors point out, their attempts to correlate meteorological factors with their observations needs further study. Purely qualitative evaluations of wind direction, wind strength)?) (only for surface winds), and cloud cover are provided with species tallies. Qualitative assessment carries over into obser- vations, where individuals are grouped under the heading of being either an “active” or “passive” migrant based upon convec- tion current utilization (Table 6) (after studies of raptor migration in Denmark by B. Bruun and O. Schelde, 1957, Efterarstraekker pa Stigsnaes, S.V. Sjaelland, D.O.F.T. 51:149-167). The useful- ness of such categorization seems questionable, since any indi- vidual of any species may either actively or passively utilize con- vection currents at any given time. Appendix B summarizes human threats to migrating raptors. Although there is little evidence of direct persecution such as shooting (Plate 4 of a “hunter” displaying 2 recently shot Steppe Eagles notwithstanding), potential for harm from chemical dumping and industrial pollution does exist in the Suez area. No mass kills have been reported, but as with most chemical contam- inants, raptors that feed, bathe, or drink while enroute through the region probably pick up harmful compounds which would be transported back to breeding territories. Overall, the report provides valuable data to the ever-growing worldwide raptor migration picture. Sherif Ben el Din’s illustra- tions evidence a keen familiarity with migrant raptors enroute through Suez. A more comprehensive assessment of observations would have been a welcome addition. Nevertheless, an 82-item literature section is provided which helps to substantiate the re- port as a basis for comparison with future raptor migration studies in the Middle East. — Jimmie R. Parrish. ERRATUM — Volume 18(4), page 159. Paul Springier should be Paul Springer. The Editorial Staff apologizes to Paul for failing to catch the misspelling before final printing. 150 News AND Reviews VoL. 19, No. 4 Announcement LIT — a Literature Retrieval System Using dBASE II — is a literature cataloguing system for use with personal computers. While the LIT System ($30.00) can be used for literature on any subject, a prepared Keyworded Data Base is available including all publications (783 items) of the Raptor Research Foundation, Inc. ($20.00 on disk or hard copy) New Data Bases are being prepared for all raptor references in Auk, Condor, Wilson Bulletin, etc. Also available is the LIT Ornithological Keyword List of nearly 900 Keywords ($15.00 on disk or hard copy for use with other systems). The following is a summary of LIT features and computer requirements: • Very quick and easy start-up, maintenance and expansion in dBASE II on most MS-DOS computers. • Rapid menu-driven data base creation, data entry and Keyword management. • Permanent, efficient and cost-effective generation of Keyworded bibliographies selected by author, title, citation, subject (Keywords), geographic location, etc. • Computer must have dBASE II software, but operator need not know how to use dBASE. • Computer must have a printer and at least two floppy disk drives (or one floppy and a hard disk) capable of reading 360K discs. RAM size must accommodate dBASE. • All source code is included for dBASE programmers. • Thorough documentation, sample data entry sheets, suggested data entry formats, and a sample Keyword List are all included. • LIT is far more than a computer program; it is also an easy to follow concept for small library/reprint file management. Eor more information and a free brochure, write Richard R. Olendorff, 6009 Viceroy Way, Citrus Heights, California U.S.A. Complete documentation (37 pp.) is available for $5.00, which will be deducted from the LIT System purchase price at the time of purchase. Proceedings of the Southeastern United States and Caribbean Osprey Symposium — published by The International Osprey Eoundation, Inc., edited by Mark A. Westall. Eleven papers, 132 pages. Copies can be ordered from The International Osprey Foundation, Inc., P.O. Box 250, Sanibel, FL 33957 USA. Price: $16.00 U.S. The Southwestern Raptor Management Symposium and Workshop will be held on the University of Arizona Campus, Tucson, 22-25 May, 1986. The Symposium will focus on raptors in the southwestern United States and adjacent Mexico. Sessions will cover raptor biology, management and research techniques, impact mitigation, and population status. There will also be a workshop on research and management priorities. For more information, or if you are interested in presenting a paper, contact Brian A. Millsap, Raptor Information Center, Institute for Wildlife Research, National Wildlife Federation, 1412 16th Street, N.W., Washington, D.C. 20036. Bird Banding by Elliott McClure, The Boxwood Press, Pacific Grove, California. 341 pp., 5!4 x 8 V 2 , paper: $15.00. — While this is a general book on bird banding there are several sections concerning raptors. McClure spent a large portion of his active professional life in Southeast Asia and much of the material is drawn from his experiences there There are 13 distinct sections varying from the geological background of migration routes (the example is from Southeast Asia), nets and snares, banding nestlings, to the art of record keeping. There are 35 index entries for birds of prey (1 1 of those are for owls). Under the section, “The Bird and its Banding Idiosyncrasies,” there is a page and a half devoted to owls and 2 pages to falconiforms. Most of the standard trapping methods used on hawks are discussed (many variations of the Bal-chatri). An interesting method of snaring the buzzard (Butastur) is discussed at some length. This book has some valuable tips for raptor banders and it is well worth looking at. — C.M. White. RAPTOR RESEARCH A Quarterly Publication of The Raptor Research Foundation, Inc. EDITOR: Clayton M. White, Department of Zoology, 161 Widtsoe Building, Brigham Young University, Provo, Utah 84602 ASSISTANT EDITOR: Jimmie R. Parrish, Department of Zoology, 159 Widtsoe Building, Brigham Young Univer- sity, Provo, Utah 84602 ASSOCIATE EDITORS Jeffrey L. Lincer - Environmental Chemistry and Toxicology Richard Clark - Order Strigiformes Ed Henckel - Family Cathartidae Gary E. Duke - Anatomy and Physiology Patrick T. Redig - Pathology, Rehabilitation and Reintroduction Jim Mosher - General Ecology and Habitat Analysis INTERNATIONAL CORRESPONDENT: Richard Clark, York College of Pennsylvania, Country Club Road, York, Pennsylvania 17405 Raptor Research (ISSN 0099-9059) welcomes original manuscripts dealing with all aspects of general ecology, natural history, management and conservation of diurnal and nocturnal predatory birds. Send all manuscripts for considera- tion and books for review to the Editor. Contributions are welcomed from throughout the world, but must be written in English. 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