Q L

‘eml Florida Field Naturalist

PUBLISHED BY THE FLORIDA ORNITHOLOGICAL SOCIETY

Vol. 15, No. 4 November 1987 Pages 85-112

FLORIDA ORNITHOLOGICAL SOCIETY
Founded 1972

Officers for 1987-1989

President: R. David Goodwin, 2531 64th Ave. S., #287, St. Petersburg, Florida 33712.
Vice-President: Richard T. Paul, National Audubon Society, 410 Ware Blvd., Suite
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Secretary: Bruce D. Neville, 8221 SW 72nd Avenue, Apt. 273, Miami, Florida 33143.
Treasurer: Caroline H. Coleman, 1701 NW 24th Street, Gainesville, Florida 32605.
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bourne, Florida 32901.

Directors 1986-1988

Lyn S. Atherton, 1100 Pinellas Bayway, 1-3, Tierra Verde, Florida 33715.
Joseph V. Marto, Jr., 8545 S. Tropical Trail, Merritt Island, Florida 32952.
John C. Ogden, 144 Mohawk St., Tavernier, Florida 33070.

Directors 1987-1989

William Dowling, 203 Toumblin Cling Rd., Ft. Pierce, Florida 33482.

Roberta Geanangel, 330 E. Swoope St., Lake Alfred, Florida 33850.

Cecil Kilmer, 2931-F W. Ashley Dr., West Palm Beach, Florida 33415.

Honorary Members

Samuel A. Grimes 1979; Helen G. Cruickshank 1980; Oliver L. Austin, Jr. 1982;
Pierce Brodkorb 1982.

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Florida Field Naturalist

PUBLISHED BY THE FLORIDA ORNITHOLOGICAL SOCIETY

Vol. 15, No. 4 November 1987 Pages 85-112

SUMMER CONCENTRATION OF AMERICAN
SWALLOW-TAILED KITES AT LAKE OKEECHOBEE, FLORIDA,
WITH COMMENTS ON POST-BREEDING MOVEMENTS

Brian A. Millsap

Florida Game and Fresh Water Fish Commission, Nongame Wildlife Program,

3900 Drane Field Road, Lakeland, Florida 33811

Abstract. — A large concentration of American Swallow-tailed Kites ( Elanoides for-
ficatus forficatus) was located at the west side of Lake Okeechobee on 26 July 1986. A
minimum of 684 kites was present on 26 July, 202 on 1 August, 100 on 23 August, and 30
on 3 September. Temporal patterns and direction of flights suggest the kites were not
migrating, but entering and departing a communal night roost. A review of historic records
suggests similar concentrations may occur at Lake Okeechobee annually. I speculate that
the site may be a staging area used by Swallow-tailed Kites prior to undertaking a trans-
Caribbean migration to South America. If true, the site offers a unique opportunity to
monitor the status of a sizeable portion of this species’ North American population.

Remarkably little is known about the post-breeding and migration
behavior of North American populations of the American Swallow-tailed
Kite (. Elanoides forficatus forficatus). The species is one of the first
nearctic to neotropical migrants to arrive in spring (late February to
early March) and depart in summer (mid- June to late August) (Sprunt
1954, Oberholser 1974), but the patterns and direction of movements are
imperfectly known. For example, North American breeders spend the
nearctic winter in South America (Brown and Amadon 1968, AOU 1983),
but their migration route is uncertain. Stevenson (1957a) and Blake
(1977) believed the species migrated overland around the Gulf of Mexico,
but Bond (1971) stated that North American kites migrate directly across
the Caribbean Sea through the Greater Antilles. More recently,
Robertson (in press) summarized observations that suggest both routes
are used.

Concentrations of apparent migrant Swallow-tailed Kites have been
reported periodically in summer along the south and west shores of Lake
Okeechobee since 1929 (Sprunt 1954) (Table 1). Although this phenome-
non has received some attention (e.g., Stevenson 1959, 1960; Edscorn

Florida Field Naturalist 15: 85-92, 1987.

85

80

FLORIDA FIELD NATURALIST

Table 1. Summary of historic accounts of summer flocks of American
Swallow-tailed Kites at Lake Okeechobee, Florida.

Date

Number

individuals

Direction

traveled

Location

Reference

7 July 1929

100 +

W

Ritta Island

Collins in Sprunt 1954

27 July 1957

05

s

Clewiston

Stevenson 1957b

27 July 1958

00

S end of lake

Stevenson 1958

10 July 1959
16-20 July 1959

94

237

S end of lake

Stevenson 1959

Horel in Robertson in
press

2 August I960

15 July 1964

50 +

100 +

W side of lake

Stevenson I960
Stevenson 1964

27 July 1904

100 +

w, s

W and S sides of lake

Stevenson 1964

11 July 1976

37

W part of lake

Sykes and White in
Ogden 1976

19 July 1978

6

SE

Moore Haven

Snyder and Ogden in
Ogden 1978

29 July 1978

12 ±

SE

Moore Haven

Snyder and Ogden in
Ogden 1978

3 August 1978

50 +

SE

Moore Haven

Snyder and Ogden in
Ogden 1978

16 August 1982

18

SE

LaBelle

Atherton and Atherton
1982

1980), the magnitude of the flight and factors responsible for the concen-
tration remain a mystery. In July 1986 1 located an unusually large aggre-
gation of Swallow-tailed Kites at the west side of Lake Okeechobee,
Glades County, Florida. Kites were periodically monitored in this area
from 26 July to 3 September 1986. Data gathered provide insights into
the migration of the species and may clarify previous comments on the
importance of western Lake Okeechobee to post-breeding Swallow-tailed
Kites.

Results

Counts and direction of movements. —On 26 July 1986 I repeatedly
drove public roads immediately south and west of Lake Okeechobee
(Buckhead Ridge to Clewiston) in an effort to observe migrating Swal-
low-tailed Kites. Between 1015-1405 h I observed 25 kites, most moving
southeast in groups of two or three. Thunderstorms interrupted observa-
tions from 1430-1645 h, but at 1650 h a soaring flock (kettle) of 102 kites
was observed over the Glades County Landfill moving west-northwest
(Fig. 1). By 1706 h the first kettle disappeared from view, but a second
kettle containing 192 + birds formed between the rim canal and the land-
fill. This kettle also moved west-northwest. Kettles continued to form
and move to the northwest until 1745 h. The total count for this 55 min

Millsap •Swallow-tailed Kite Movement

87

flight was 684 + kites. I believe this was a conservative estimate number
because some kites were undoubtedly beyond my range of vision, and
the pattern of movement made it unlikely birds were counted more than
once.

I returned to the area at 0855 h on 27 July. At 0939 h a loose kettle
of 15 Swallow-tailed Kites appeared on the northwest horizon. This kettle
flew to the southeast until reaching the Herbert Hoover Dike (rim canal)
at the western perimeter of Lake Okeechobee approximately 10 km north
of Moore Haven. The kettle continued moving southeastward along the
rim canal. Several additional groups, ranging in size from 7 to 100 indi-
viduals, passed overhead along the same track between 0945-1100 h. A
total of 147 kites was observed flying to the southeast. The morning
flight was much more dispersed than that of the preceeding evening, and
many kites probably passed beyond my range of vision to the north and
south.

Figure 1. Map of southwestern Lake Okeechobee and western Fisheating Creek, Glades
Co., Florida, showing relative size and direction of travel of American Swallow-tailed
Kite kettles (dark arrows) observed between 1500-1800 h on 26 July, 1 August, 23 Au-
gust, and 3 September 1986. Large arrows represent kettles of >50 kites; small arrows
represent kettles of <50 kites. Hatching denotes cypress swamp on Fisheating Creek,
and broken lines denote dikes.

88

FLORIDA FIELD NATURALIST

I conducted afternoon (1600-1800 h) counts on 1 August, 23 August,
and 3 September. Total Swallow-tailed Kite counts for these days were
202, 100, and 30, respectively. These evening flights were more dispersed
than on 26 July, and the location of the main flight line varied from SR
27 6 km west of Moore Haven to 10 km northeast of Lakeport (Fig. 1).
The direction of movement varied on each day; however, compass bear-
ings taken along flight lines of each kettle intersect in an extensive cyp-
ress swamp on Fisheating Creek (Fig. 1).

Data collected from evening counts and the single morning count re-
vealed a possible temporal pattern in Swallow-tailed Kite movements.
During the single morning observation period, kites did not appear until
0939 h, and the magnitude of the flight peaked between 1030-1045 h.
Large numbers of kites first appeared in the evening about 1530 h, and
counts peaked between 1615-1715 h (Fig. 2).

Behavior.— The kettling behavior of Swallow-tailed Kites was similar
to that of other soaring falconiforms (Heintzelman 1975). During evening
flights, individuals tended to gather in loose flocks 10-30 m above ground
level (agl) over the rim canal. These loose flocks appeared to move paral-
lel to the canal until a thermal or suitable updraft was encountered,
whereupon the flock would rapidly gain height. Additional birds usually
joined such rising flocks from below and above, eventually forming a
compact kettle. Occasionally kettles ascended out of sight, but more
commonly small groups would leave the kettle as they approached the
upper limits of visibility (about 1000 m agl). Departing groups typically
formed loose lines, gliding in a gentle descent in the direction of travel.
Three groups that were followed after leaving a kettle glided for 8.5-10.0
km before soaring to regain altitude.

Discussion

The periodic accounts of large flights of Swallow-tailed Kites around
Lake Okeechobee in summer have led to speculation that the lake lies
along a major migration route for the species (Stevenson 1958, 1959,
1960, 1964). There is little doubt that large numbers of kites migrate
through south Florida (Stevenson 1964, Ogden and Stevenson 1965,
Robertson in press). Stevenson (1964) felt that perhaps all Swallow-tailed
Kites in the southeastern United States used this pathway. Presumably,
these birds continue south across the Caribbean Sea to South America
(Bond 1971, Robertson in press).

My observations support arguments that a major Swallow-tailed Kite
migration route passes through south Florida. Although the size of the
United States breeding population is not known, Robertson {in Cely
1979) estimated that 250-400 pairs nested in south Florida. J. Cely (pers.
comm.) estimated that 50-60 pairs occur on the Francis Marion National

Millsap- Swallow-tailed Kite Movement

89

Forest in South Carolina. A few nesting pairs occur in the Okefenokee
Swamp, Georgia; northwestern Florida; Mobile River Delta, Alabama;
and Atchafalaya River Basin, Louisiana (Parker 1984). Given the gener-
ous assumption that a minimum of 50 pairs breed annually in each of the
latter areas, and each pair fledges 2.0 young, the population size in the
southeast in summer could be as large as 2,600 individuals. Thus, a
minimum of 26% of this estimated population was present at Lake
Okeechobee on 26 July 1986. The actual size of the population is likely
smaller; average fledging success and the number of adults in some sub-
populations are probably lower. Additionally, kites from northwestern
Florida, Alabama, and Louisiana may follow a more western migration
route through Texas and eastern Mexico (Stevenson 1957a, Robertson in
press).

The direction of Swallow-tailed Kite movements in the late afternoon
at Lake Okeechobee was the reverse of the expected southward orienta-
tion of migrants in south Florida. Whereas it is possible kites were mig-
rating north following a route that would take them around the northern
Gulf of Mexico, I believe another explanation is more plausible. The
reversal in the direction of movements between morning and afternoon
flights, convergence of evening flight lines, and the timing of flights
suggest birds were moving to and from a communal night roost. I was
unable to verify the presence of such a roost due to access and logistic
constraints; nevertheless, this hypothesis best explains all observations.
Swallow-tailed Kites are typically gregarious during migration (Bent
1937, Sprunt 1954, Snyder 1975), and communal roosting has been ob-
served previously at Corkscrew Swamp, Florida (J. Hansen and T.
Below in Ogden 1977) and in South Carolina (J. Cely, pers. comm.).

NO. KITES/
HOUR

OBSERVATION

Figure 2. Plot of number of American Swallow-tailed Kites observed per hour of obser-
vation at western Lake Okeechobee, Florida. Data for 0900-1100 h are based only on
27 July 1986. Data for 1500-1800 h were collected on 26 July, 1 August, 23 August, and

3 September 1986.

90

FLORIDA FIELD NATURALIST

The question of why Swallow-tailed Kites concentrated at this site
cannot be answered with available data, but speculation is possible. As-
suming kites do follow a trans-Caribbean migration route to South
America, there is little evidence the birds stop to forage in either the
Greater or Lesser Antilles; migrant flocks only have been reported from
Cuba and Jamaica, and the species does not appear to occur regularly on
either island (Barbour 1943, Bond 1971). This suggests kites may make
the crossing in one flight at high altitude. Many birds that undertake
such long-distance migratory flights, including some falconiforms that
breed in North America but “winter” in the neotropics, accumulate de-
posits of peritoneal and subcutaneous fat shortly before departing (Welty
1975, Smith 1985). I suggest that Swallow-tailed Kites may pause during
(e.g., in the case of more northern birds) or before their southward mig-
ration in south Florida to build-up fat reserves. Given the species" gre-
garious nature, concentrations in the vicinity of large expanses of suitable
foraging habitat would be expected. J. Cely (pers. comm.) noted that
radio-tagged Swallow-tailed Kites in South Carolina foraged extensively
over freshwater marshes. This community is abundant on the south and
west sides of Lake Okeechobee, and this may in part explain the presence
of the observed kite concentration. However, large expanses of freshwa-
ter marsh exist further south in Florida in the Everglades, but few Swal-
low-tailed Kites are observed there in summer (W. Roberson, pers.
comm.). It seems likely the concentration at Lake Okeechobee is in part
food determined, although the important prey species are unknown. A
second contributing factor may be the juxtaposition of marshes and ex-
tensive cypress swamp, which affords suitable roosting habitat, on the
west side of Lake Okeechobee at Fisheating Creek.

More than a single season of observations are needed to determine
whether Swallow-tailed Kites concentrate annually at Lake Okeechobee.
Despite numerous reports that suggest concentrations occur regularly
(Table 1), Edscorn (1980) searched for migrating kites from the Big Cyp-
ress Indian Reservation to Lake Okeechobee on 14 July 1980 but saw
only nine birds. The question of regularity is of more than academic
importance. The Swallow-tailed Kite has declined drastically in abun-
dance and range in North America since the late 18O0"s (Cely 1979, Parker
1984, Robertson in press), and the species is currently a Category 2
candidate for federal listing as a threatened or endangered species
(TJSFWS 1985). Information on current population status and trend is
required to accurately assess the need for management. If western Lake
Okeechobee is an annual staging area for migrant Swallow-tailed Kites,
it offers a unique opportunity to monitor the status of the southeastern
population.

Millsap •Swallow -tailed Kite Movement

91

Postscript

At 1730 h on 4 August 1987, Lance Ham and I located the communal
Swallow-tailed Kite roost by helicopter. The roost was in the general
area suspected in Fig. 1, but its exact location is being withheld to insure
the security of the site. Photographs taken from the air revealed 882
perched kites, and an additional 200 or so kites were observed flying
toward the site. I returned and counted 1,339 kites leaving the roost
between 0824 h and 0904 h on the morning of 7 August 1987. If the
estimated population size generated in this paper is correct, approxi-
mately 50% of the United States population was using the site on this
day. The number of kites at the site had declined to 523 by 17 August
1987. The roost was located in an insular, open stand of small (< 10 m
tall) cypress trees about 1 ha in size. Roosting kites crowded into the
tops of about half of the trees in the stand, with some trees supporting
over 100 birds. Water depth under the roost was about 1 m on 6 August.
A deep, densely vegetated freshwater marsh surrounded the roost site,
and isolated it from more extensive cypress stands 0.3 km to the north-
west and south. The closest uplands were 0.5 km to the west.

Acknowledgments

I thank N. F. R. Snyder for calling my attention to Swallow-tailed Kites at Lake
Okeechobee. W. B. Robertson, Jr., graciously allowed me to cite portions of his unpublished
manuscript on the American Swallow-tailed Kite for the Handbook of North American
Birds. J. E. Cely provided useful information on post-breeding activities of kites in South
Carolina. R. T. Paul and F. E. Lohrer kindly brought several important references to my
attention. J. E. Cely, J. A. Gore, F. E. Lohrer, K. D. Meyer, W. B. Robertson, Jr., and
J. A. Rodgers, Jr. made many helpful comments on the manuscript.

Literature Cited

AOU. 1983. Check-list of North American birds. Sixth ed. Washington, D.C.: American
Ornithologists’ Union.

Atherton, L. S., and B. H. Atherton. 1982. The nesting season— -Florida region.
Amer. Birds 36: 168-171.

Barbour, T. 1943. Cuban ornithology. Cambridge, Massachusetts: Memoirs of the Nuttall
Ornithol. Club No. 9.

Bent, A. C. 1937. Life histories of North American birds of prey. Vol. 1. Washington, D.
C.: U. S. Nat. Mus. Bull. 167.

Blake, E. R. 1977. Manual of neotropical birds. Vol. 1. Chicago, Illinois: Univ. Chicago
Press.

Bond, J. 1971. Birds of the West Indies. Second ed. Boston, Massachusetts: Houghton
Mifflin.

Brown, L., and D. Amadon. 1968. Eagles, hawks and falcons of the world. Vol. 1.
London: Country Life Books.

Cely, J. E. 1979. Status of the Swallow-tailed Kite and factors affecting its distribution.
Pages 144-150 in Proc. of the First South Carolina Endangered Species Symposium (D.
M. Forsythe and W. B. Ezell, Jr., eds.). Columbia, South Carolina: South Carolina
Wildlife and Marine Resour. Department.

92

FLORIDA FIELD NATURALIST

Edscorn, J. B. 1980. The nesting season — Florida region. Amer. Birds 34: 887-889.
Heintzelman, D. 1975. Autumn hawk flights. New Brunswick, New Jersey: Rutgers
Press.

Oberholser, H. C. 1974. The bird life of Texas. Austin, Texas: Univ. Texas Press.
Ogden, J. C. 1976. The nesting season — Florida region. Amer. Birds 30: 945-948.

Ogden, J. C. 1977. The nesting season — Florida region. Amer. Birds 31: 1128-1130.

Ogden, J. C. 1978. The nesting season — Florida region. Amer. Birds 32: 1151-1153.

Ogden, J. C., and H. M. Stevenson. 1965. The nesting season — Florida region. Audu-

bon Field Notes 19: 534-537.

Parker, J. W., Jr. 1984. Status reports: the American Swallow-tailed Kite. Eyas 7: 12-13.
Robertson, W. B., Jr. In press. American Swallow-tailed Kite. Elanoides forficatus. In
Handbook of North American birds, Vol. 4 (R. S. Palmer, ed.). Washington, D. C.:

Smithsonian Inst. Press.

Smith, N. G. 1985. The path between North America and limbo: the “wintering grounds”
syndrome and future research on migratory raptors. Pages 387-393 in Proc. Hawk
Migration Conf. IV (M. Harwood, ed.). Salem, Virginia: Hawk Migration Assoc, of
North America.

Snyder, N. F. R. 1975. Breeding biology of Swallow-tailed Kites in Florida. Living Bird
13: 73-97.

Sprunt, A., Jr. 1954. Florida bird life. New York: Coward-McCann.

Stevenson, H. M. 1957a. The relative magnitude of the trans-gulf and circum-gulf spring
migration. Wilson Bull. 69: 39-77.

Stevenson, H. M. 1957b. The nesting season— Florida region. Audubon Field Notes 11:
399-402.

Stevenson, H. M. 1958. The nesting season— Florida region. Audubon Field Notes 12:
405-408.

Stevenson, H. M. 1959. The nesting season — Florida region. Audubon Field Notes 13:
426-429.

Stevenson, H. M. 1960. The nesting season — Florida region. Audubon Field Notes 14:
444-446.

Stevenson, H. M. 1964. The nesting season — Florida region. Audubon Field Notes 18:
503-505.

USFWS. 1985. Endangered and threatened wildlife and plants; review of vertebrate wild-
life; notice of review. Fed. Reg. 50: 37958-37967.

Welty, J. C. 1975. The life of birds. Second ed. Philadelphia, Pennsylvania: W. B. Saun-
ders.

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ROOSTING BEHAVIOR OF THE
YELLOW-SHOULDERED BLACKBIRD

William Post and Kathleen W. Post

The Charleston Museum, 360 Meeting Street,

Charleston, South Carolina 29403

Abstract.— -In southwestern Puerto Rico, Yellow-shouldered Blackbirds ( Agelaius
xanthomus), Shiny Cowbirds ( Molothrus bonariensis), and Greater Antillean Grackles
( Quiscalus niger) use communal secondary (diurnal) and primary (nocturnal) roosts
throughout the year. Secondary roosts usually are located in the subcanopy of trees near
food sources, and may act as centers for integration of flock activity, particularly exchange
of information about predator location. Roosting in shaded sites allows these dark-plumaged
birds to avoid hyperthermia. Primary roosts are located in predator-free sites like small
islands, electric power stations, or coconut palms (Cocos nucifera) with rat guards. Primary
roosts of Yellow-shoulders were largest during the summer and fall, which reflects the
concentration of the population around breeding colonies. Shiny Cowbirds used the same
roosts, mainly from early summer through early fall (May-September). Yellow-shoulders
do not stay in the nesting colonies at night unless they are incubating or brooding, but
return to the communal roosts. During the non-breeding season (October-March) the pop-
ulation was more dispersed and used many roosts. Yellow-shoulders and Greater Antillean
Grackles have similar roost-entering patterns, but Shiny Cowbirds arrive later, and their
arrival is more synchronized. All three species apparently use the rapid light changes
occurring around sunset as cues for roost-entering. All species were sensitive to distur-
bances in the roosts, and readily relocated to new sites when disturbed. Predator mobbing
was common. For all three species roost-leaving is more synchronized than roost-entering.

The Yellow-shouldered Blackbird (. Agelaius xanthomus) is endemic
to Puerto Rico and Mona Island. The species decreased precipitously
between 1940 and 1975 (Post and Wiley 1976), and this trend toward
extinction has continued. In 1975 the main population center was in
southwestern Puerto Rico. During the winter of 1974-1975, there were
about 1,663 individuals using roosts around La Parquera (Post and Wiley
1977a). In 1981-1982 this number had decreased to 266 birds (pers. obs.).
Censuses conducted in 1985-1986 indicate that the population may now
be stabilizing around the latter figure (Silander 1986). The causes for the
species’ decline are discussed elsewhere (Post and Wiley 1976, 1977a,
1977b; Post 1981a, 1981b). The main factor affecting its status is brood
parasitism by the Shiny Cowbird (. Molothrus bonariensis) (Post and
Wiley 1977b; Wiley 1985; Cruz et al. 1985).

Roosting is an important aspect of the Yellow-shouldered Blackbird’s
biology, especially as it shares roosts with its parasite, the Shiny Cow-
bird. In the nesting season the species leave roosts together, so cowbirds
may follow Yellow-shoulders to their nest sites. In addition, prolonged
association between host and parasite in roosts increases the probability

Florida Field Naturalist 15: 93-105, 1987.

93

94

FLORIDA FIELD NATURALIST

of their synchronizing breeding seasons (Post and Wiley 1977b). Under-
standing the roosting patterns of both species will enable us to determine
more effective ways of improving the status of the endangered blackbird.

Study Area and Methods

The study was conducted from 14 January 1973 to 15 February 1976. The study area
extended along the southwestern coast of Puerto Rico from Bahia Montalva to Boca Prieta
(Buye) (Fig. 1). We also visited inland roosts at Lajas and San German. The vegetation
and climate of the region are described elsewhere (Post 1981b). To census roosts on offshore
cays, we anchored a boat so that all flight-lines could be seen simultaneously. If this was
not possible, we counted all flights on one side of the island, and returned the next day to
cover the other side. One or two persons counted the birds, while another recorded. All
birds were recorded at one-minute intervals as they entered the roost. Evening counts
were conducted from 120 min before sunset to 40 min after sunset. We made morning
counts from 30 min before sunrise until all birds had left the roost. To census birds using
power station roosts, we counted birds after they had settled. All roost occupants could be
seen, because they sat on exposed wires and superstructures. We used standard deviation
as the measure of statistical dispersion.

Figure 1. Study site in southwestern Puerto Rico. Key to numbered localities: 1 =
Pitahaya, 2 = Salinas Arcelay, 3 = Punta Tocon, 4 = Isla Guayacan, 5 = Isla La
Cueva, 6 = Collao, 7 = Lajas Experimental Station, 8 = Caballo Blanco, 9 = Cayo
Enrique, 10 = Isla Magueyes, and 11 = Salinas Carlo.

Post and Post® Blackbird Roosting Behavior

95

Results and Discussion

Secondary Roosts.— In Puerto Rico icterines use nocturnal and diur-
nal communal roosts throughout the year. Diurnal or secondary roosts
(Ward and Zahavi 1973) were close to feeding grounds. For example,
Yellow-shouldered Blackbirds, Greater Antillean Grackles ( Quiscalus
niger) and Shiny Cowbirds that fed in monkey enclosures on La Oueva
Island roosted in a shoreline section of red mangrove ( Rhizophora man-
gle) canopy, 20-40 m from the nearest feeding sites. The number of birds
using this roost varied, but usually 25-100 birds, spread over about 600
m2, were present at midday. Birds altered foraging bouts with variable
lengths of stay in the secondary roosts, where they rested, preened and
vocalized. Yellow-shoulders also occasionally carried food such as pieces
of monkey biscuit into the secondary roost. Periodically groups of up to
20 birds would fly out to feed. Secondary roosts were used regularly only
during the non-breeding season (Gctober-April), When nesting, birds
visiting the communal feeding sites usually returned immediately to their
nests.

In secondary roosts icterines responded in concert to predators, in-
cluding humans. When Turkey' Vultures ( Cathartes aura) or American
Kestrels (. Falco sparverius) flew over a secondary roost, all three species
of icterines reacted by immediately becoming quiet and often diving as
a group into denser vegetation. All three species jointly mobbed terrest-
rial predators. For example, we netted birds 25 m from a secondary
roost on La Gueva, and when a captured Yellow-shouldered Blackbird
screamed while being handled, grackles, cowbirds and Yellow-shoulders
rapidly left the roost, flying within 5-10 m to mob us.

At the Lajas Experimental Station icterines utilized the upper canopy
of several large oxhorn bucida ( Bucida buceras) for secondary roosts. On
El Guayacan Island flocks of Yellow-shoulders feeding in the monkey
enclosures used stands of black mangroves (. Avicennia germinans ), 3-4
m high and 15 m distant, for secondary roosts. These trees did not pro-
vide as much shade as the red mangrove or oxhorn bucida roosts, but
the birds found additional shade under the monkey shade structures in
the enclosures where they fed.

On 15 February 1976, we recorded inter-individual distances for Yel-
low-shoulders perched next to each other on the cross-bars of shade
structures in some monkey enclosures. The average distance between 21
birds was 12.4 ±4.0 cm. Throughout the period of the study, in addition
to allopreening, we observed occasional physical contact between Yellow-
shoulders in secondary roosts.

Wetmore (1927) commented on the diurnal roosting of Yellow-shoul-
ders, and pointed to its significance as a means of escaping the effects of
midday insolation. Mist-netted Yellow-shoulders that were exposed to

96

FLORIDA FIELD NATURALIST

more than 3 min of midday sun usually died. The use of daytime roosts
may be crucial for dark-plumaged birds in the subtropics, especially when
they forage in the open in the middle of the day.

Primary Roosts.— Yellow-shouldered Blackbirds, Shiny Cowbirds
and Greater Antillean Grackles used nocturnal or primary communal
roosts all year (Table 1). About the same numbers of Yellow-shoulders
and grackles used the roosts throughout the year, but the number of
Shiny Cowbirds varied with season. The largest numbers of cowbirds
were in the communal roosts in the summer and fall, which corresponds
to the breeding season of the Yellow-shoulder (Post 1981b). During the
dry season (October-March) the Shiny Cowbirds probably move to mois-
ter areas outside the arid coastal zone. For example, the largest number
of cowbirds recorded at any winter roost (3,525) was in San German on
12 February (Appendix).

Unlike secondary roosts, primary roosts were isolated; most were on
small cays or mangrove peninsulas (Fig. 1). Icterines also roosted in
electric transformer stations and in palm plantations. All of these sites
were inaccessible to predators. Offshore mangrove cays and peninsulas
were protected by water. Transformers were surrounded by chain-link
fences, and the wires and steel beams of the structures were too smooth
for climbing predators. These stations also were floodlit at night. Coconut
palms ( Cocos nucifera) that blackbirds used for roosting had metal rat
guards.

Yellow-shouldered Blackbirds and other icterines roosted with other
species like Gray Kingbirds {Tyr annus dominicensis) (Post 1982) and
Mourning Doves ( Zenaida macroura). Larger birds such as Cattle Eg-
rets ( Bubulcus ibis), Brown Pelicans (. Pelecanus occidentalis ) and Mag-
nificent Frigatebirds ( Fregata magnificens) often roosted on the same
mangrove cays, but blackbirds did not roost in areas occupied by these
species.

Yellow-shouldered Blackbirds and other icterines commonly flew to-
gether to their roosts. Along the coast, the final gathering points for
roost flights were in the canopy of mangroves on the mainland opposite,
and usually closest to the roost. The size of roost-bound flocks varied,
and depended perhaps on the number of birds using the roost (Table 2),
as well as nearness to sunset. Shiny Cowbirds formed larger flocks (x =
42) than did either Yellow-shouldered Blackbirds or Greater Antillean
Grackles, although the largest Yellow-shoulder flock (150) was the same
size as the largest cowbird flock. The average flock size of Yellow-shoul-
ders (x = 32) was larger than the grackle’s (x = 15).

Flight paths to the roosts varied according to the roosts’ distances
from the mainland gathering points and the wind conditions. Roosts close
to the gathering point, and not separated by a wide stretch of water,
were entered by flights 1-2 m above water. In departing for a roost far

Table 1. Seasonal variation in species composition of primary roosts on the southwest coast of Puerto Rico, 1973-1975.

Post and Post* Blackbird Roosting Behavior

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lLa Parquera Harbor.

JCollao, adjacent to La Cueva.

98

FLORIDA FIELD NATURALIST

offshore (over 250 m), birds at the gathering point flew up in mass, and
continued to fly together at a height of 20-30 m. As the flock approached
the roost, it gradually lowered altitude until it was 30-50 m off the roost
cay, at which time it had reached a height of 0.5-1. 5 m. When the head-
wind was too strong, the departing flocks would turn back repeatedly to
the departure point.

When Yellow-shouldered Blackbirds flew low over the water and the
wind was strong, they risked being engulfed by a wave. On 7 September
1973, we saw three Yellow-shoulders fall in the water as they flew to
roost on Collao, with winds 25-33 km/h. When the birds were a short
distance above the water, one bird fell in, about 40 m from Collao. It
swam to the cay in 6 min 40 sec, against a strong southeast wind. A
second bird fell in 30 m from Collao. It initially scampered, gallinule-like,
over the water until its wings were wet and it sank, but it was able to
swim to the island in 2 min 31 sec. A third bird fell in 20 m offshore, and
was in the water 2 min 13 sec. All three swam strongly, with only their
necks and backs out of the water. On 3 August 1975, we saw a Yellow-
shoulder chase another into the roost, and about 5 m offshore, the pur-
suer attempted to grab the tail of the other bird, and knocked it into the
water. These occurrences of adult Yellow-shoulders falling in the water
may be related to their molting during August-September; with remiges
missing overwater flight against a wind becomes hazardous.

The temporal behavior of Yellow-shouldered Blackbirds and Greater
Antillean Grackles arriving at primary roost was similar (Table 3; Fig.
2). The average time of first arrival of both species was 104-105 min
before sunset; 90% of the population were in the roost by 14 min before
sunset, and the average last arrival in the roost was 1-2 min after sunset.
The Shiny Cowbird arrived later (79 min before sunset) and completed
its roosting movements in a shorter period (76 min vs. 102 min for each
of the other species). The average light intensity for Yellow-shoulders
arriving at five roosts was 5,768 foot-candles (fc). The average light in-
tensity at the time that 90% of the Yellow-shoulders had arrived was 313
fc, and the average intensity on termination of flight was 79 fc. Tropical
icterines, like temperate zone species, apparently use the rapid light
changes taking place after sunset as cues for their roosting movements
(Krantz and Gauthreaux 1975).

Because of the latitude, the seasonal variation in the time of sunset
is slight (i.e., 1 h-25 min from 25 June to 16 November). This small
difference is reflected in a lack of pronounced seasonal variation in the
temporal pattern of roosting behavior (Fig. 3).

In the fall fewer and larger roosts were used than in other seasons;
for example, the Collao roost apparently served the whole area from
Pitahaya to La Parguera (Fig. 1). This roost began forming during the
breeding season, and it was closest to the main breeding grounds on the

Post and Post •Blackbird Roosting Behavior

99

adjacent mainland (Salinas Carlo and Salinas Arcelay) and feeding areas
on La Cueva and El Guayacan. Collao was not occupied in the winter or
spring and at those times blackbirds used several smaller roosts such as
Pitahaya, Bahia Montalva, Punta Tocon, Caballo Blanco, or Magueyes
(Fig. 1). The use of many smaller roosts in the winter reflects more
dispersed feeding patterns than in the summer, although individual birds
flew long distances to certain preferred roosts. For example, during
March and April 1974 male “OXOA” and female “AGOY” fed during the
day in La Parquera, but flew 5 km nightly to roost at Bahia Montalva,
rather than using the Caballo Blanco roost, 1 km from their feeding
grounds.

Around La Parquera at least one roost was active all year: Magueyes,
Caballo Blanco, or Cayo Enrique. Similarly, Bahia Sucia was a year-
round roost, although like the roosts in La Parquera, numbers of birds
using it varied with the season. The relative representation of each
species is probably important in determining the permanence of a roost:
although one species might abandon a roost, it could be maintained by
the others. Yellow-shoulders use communal roosts even during the nest-
ing season; males do not roost in the nest vicinity, and females stay only
about 20 days, when they are incubating and brooding (Post 1981b).

TIME (MIN) IN RELATION TO SUNSET (O)

Figure 2. Roost-entering pattern of three species of icterines at Collao, 3 August 1975.
Sunset at 1905 h. Numbers of birds entering roost were: Yellow-shouldered Blackbird
(YSBB), 1044; Greater Antillean Grackle (GAG), 1107; Shiny Cowbird (SC), 1867.

100

FLORIDA FIELD NATURALIST

Table 3. Comparisons between the evening roosting behavior of three species of
icterines using primary roosts on the southwestern coast of Puerto Rico.

Variable

Y ellow-shouldered
Blackbird

Greater Antillean
Grackle

Shiny Cowbird

Time of first
arrival at roost1

-105 ± 19(15)2'3

-104 ±15(16)

-79 ± 24(15)

Time by which 90% of
birds had entered roost1

-14 ± 18(21)

-14 ± 16(20)

-18 ± 10(14)

Time of last arrival1

-1± 20(16)

2 ± 18(16)

-4 ± 13(15)

Average duration of
roost flight (min)

102 ± 20(14)

107 ± 22(16)

76 ± 17(10)

Average rate of entry
(bird/min)

6 ± 4(14)

7 ± 4(14)

17 ± 16(10)

Minutes in relation to sunset.

2 Values represent mean ± 1 SD.

3Values in parentheses are sample sizes.

The three icterine species were sensitive to disturbances at their
roosts and switched to alternate sites, of which there were many nearby.
For example, we found five roost sites within 3 km of La Parquera, each
used only one at a time. The rapidity of response of blackbirds to distur-
bances in their roosts is shown by the following occurrence. On the even-
ing of 8 May 1974, we gave distress squeaks and clapped our hands in
the Magueyes roost. Many birds, mainly Greater Antillean Grackles,
responded by flying overhead in mass, scolding and hovering above, then
landing in nearby treetops to continue mobbing. At 12 min before sunset
we started our boat motor and the noise again disturbed the birds, as
flocks of 50-100 grackles and Yellow-shouldered Blackbirds flew out of
the roost to Caballo Blanco, 440 m away. We then went to Caballo
Blanco, where birds were still arriving from Magueyes. The roost-switch-
ing of these birds lasted until 3 min after sunset. Some flocks landed on
Caballo Blanco only to fly up again, returning to the original roost on
Magueyes, although most of the newly arrived flocks stayed.

Yellow-shouldered Blackbirds and other icterines roosting in man-
groves occupied the lower and middle canopies, a height which varied
from site to site. For example, on Collao Yellow-shoulders and Shiny
Cowbirds roosted at 4. 5-7. 5 m where the mangroves were about 9 m
high, whereas on Caballo Blanco, these two species roosted at 6-9 m in
12 m high mangroves. Roosting icterines used the inner parts of roosting
cays, usually 5-10 m away from the water’s edge. In tall mangroves,
such as on Caballo Blanco, the subcanopy had few leaves and twigs and
was little used by roosting icterines. Before dark roosting birds mainly
rested and preened. Intense calling bouts by icterines were often alter-

Post and Post* Blackbird Roosting Behavior

101

nated with periods of silence. Roosting Yellow-shoulders used most of
their vocalizations, and no special displays were associated with roosting.

In the morning, Yellow-shouldered Blackbirds and other icterines
left the roosts during a shorter time compared to entering the roost (Fig.
4). Before leaving the roost, birds moved up to the tops of the mangroves
and called continuously. Departing flocks flew up over the roost to an
altitude of 20-30 m, often circled, then flew toward the mainland. After
reaching the mainland, flocks of individuals moved toward their main
feeding grounds, frequently stopping along the way to feed or rest. Dur-
ing December 1972- January 1973 the average time of arrival of the first
birds on the feeding grounds on La Cueva was 27.9 ±7.3 min after
sunrise, or 39.9 ±7.3 min after the birds left the roost on Caballo Blanco
(N = 14 days). The average rate of travel over the 4.5 km distance
between the roost and La Cueva was 117 ± 20 m/min.

Conclusions

The daily roosting movements of the subtropical Yellow-shouldered
Blackbird are examples of diel migrational responses (Gauthreaux 1980).
Daily periodicity in communal roosting is evident throughout the year.

Because Yellow-shouldered Blackbirds often feed in groups during
the day, but also are subject to nocturnal predation, it is not possible to
use this species to test Ward and Zahavi’s (1973) hypothesis regarding
the information transfer function of communal assemblages. However, it

Figure 3. Seasonal changes in roost-entering behavior of Yellow-shouldered Blackbirds
based on data summarized in Table 3. Solid line represents time of sunset.

102

FLORIDA FIELD NATURALIST

is likely that predator avoidance is a significant factor in determining the
location of nocturnal roosts of the Yellow-shoulder. This is deduced from:
(1) their use of traditional predator-free roost sites that are often reached
by long flights; (2) the blackbirds’ sensitivity to predators in the roosts,
and their readiness to mob intruders and to desert disturbed roosts; and
(3) their sharing roosts with Gray Kingbirds, a species whose communal
roosting appears to aid mainly in predator avoidance (Post 1982).

The secondary roosts used by Yellow-shoulders provide essential
shade for these dark-plumaged birds. They also serve as refuges from
raptors. Large shade trees near appropriate foraging areas may be im-
portant factors in determining the diurnal distribution of Yellow-shoul-
ders and other icterines in the subtropics. Management plans for the
Yellow-shoulder should consider the distribution of secondary and pri-
mary roosts, in relation to major communal feeding and nesting areas.

The relationship between the Yellow-shouldered Blackbird and the
Shiny Cowbird in the communal roosts deserves further study. During
the breeding season Shiny Cowbirds do not closely associate with forag-
ing Yellow-shoulders. Yellow-shoulders are usually solitary feeders at

60-

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TIME (MIN) IN RELATION TO SUNRISE (0)

Figure 4. Roost-leaving pattern of three species of icterines at Caballo Blanco, 15
December 1974. Number of birds: Yellow-shouldered Blackbird (YSBB), 147; Greater
Antillean Grackle (GAG), 506; Shiny Cowbird (SC), 45.

Post and Post •Blackbird Roosting Behavior

103

this time, and use arboreal, oriole-like foraging tactics (Post 1981b). Cow-
birds usually feed on the ground and are more closely associated with
Greater Antillean Grackles. Further, most Shiny Cowbirds (>90% of the
population) leave the southwestern coastal zone in the winter. When the
bulk of cowbird population returns to the Yellow-shoulder breeding areas
in the spring, communal roosting may allow rapid synchronization of the
two species’ breeding behavior. The communal roosts may be especially
advantageous to any cowbirds that arrive after the blackbirds have al-
ready switched from communal to solitary foraging sites.

Acknowledgments

We gratefully acknowledge the logistic support of the Caribbean Primate Research
Center, John Herbert and Eric Phoebus, scientists in charge. While working in La Parqu-
era, we were supported by U.S. Health Service Grant DA-0070, principal investigator, J.
G. Vandenbergh. We are especially grateful to Vandenbergh for his encouragement of
Yellow-shouldered Blackbird research. Micou Brown helped to conduct many of the roost
counts. Michael Gochfeld provided roost data for 1965. The manuscript benefited greatly
from the critical comments of James W. Wiley and an anonymous reviewer.

Literature Cited

Cruz, A., T. Manolis, and J. W. Wiley. 1985. The Shiny Cowbird, a brood parasite
expanding its range in the Caribbean region. A.O.U. Ornithological Monograph No. 36:
607-620.

Gauthreaux, S. A., Jr. 1980. The influences of long-term and short-term climatic
changes on the dispersal and migration of organisms. Pages 103-174 in S. A. Gauth-
reaux, Jr. (ed.), Animal migration, orientation and navigation. New York: Academic
Press.

Krantz, P. E., and S. A. Gauthreaux, Jr. 1975. Solar radiation, light intensity, and
roosting behavior in birds. Wilson Bull. 87: 91-95.

Post, W. 1981a. The prevalence of some ectoparasites, diseases, and abnormalities in the
Yellow-shouldered Blackbird. J. Field Ornith. 52: 16-22.

Post, W. 1981b. Biology of the Yellow-shouldered Blackbird— Ageisms on a tropical is-
land. Bull. Florida State Museum 26: 125-262.

Post, W. 1982. Why do Grey Kingbirds roost communally? Bird Behaviour 4: 46-49.
Post, W., and J. W. Wiley. 1976. The Yellow-shouldered Blackbird — present and future.
Amer. Birds 30: 13-20.

Post, W., and J. W. Wiley. 1977a. The Shiny Cowbird in the West Indies. Condor 79:
119-121.

Post, W., and J. W. Wiley. 1977b. Reproductive interactions of the Shiny Cowbird and
the Yellow-shouldered Blackbird. Condor 79: 176-184.

Silander, S. 1986. Revised minutes, First Annual Yellow-shouldered Blackbird Meeting,
13 January 1986 (revised 9 July 1986). Unpubl. rept.

Ward, P., and A. Zahavi. 1973. The importance of certain assemblages of birds as
‘information-centres’ for food-finding. Ibis 115: 517-534.

Wetmore, A. 1927. The birds of Porto Rico and the Virgin Islands. New York Acad. Sci.

Survey of Porto Rico and the Virgin Islands 9: 409-571.

Wiley, J. W. 1985. Shiny Cowbird parasitism in two avian communities in Puerto Rico.
Condor 87: 165-176.

Appendix. Summary of blackbird roost counts in southwestern Puerto Rico, 1965-1975.

104

FLORIDA FIELD NATURALIST

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Post and Post* Blackbird Roosting Behavior

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NOTES

Successful nesting of Black-shouldered Kites in the Everglades of Broward County,
Florida. — Since the late 1960’s the Black-shouldered Kite ( Elanus caeruleus) has expanded
its range in Arizona, California, New Mexico, and Oklahoma (Gatz et al. 1986). Toups et
al. (1985) documented the first appearance and nesting of this kite in Mississippi in 1983.
Due to the kite’s regular fall and winter sightings in Florida, Hoffman (1985) suggested its
eventual recolonization. Kale (1974) reported 11 observations from 1961 to 1973, including
one immature bird. Stevenson (pers. comm.) recorded 14 observations since 1974. From
21 September to 25 October 1984 an adult kite frequented ranch land west of Ft. Lauderdale
(Atherton and Atherton 1985). A kite was observed over Margate during the 1985 Ft.
Lauderdale Christman Bird Count (Bolte 1986). Although there are three records of previ-
ous nesting attempts in Florida, the last on 4 February 1910, none were successful (Sprunt
1954).

On 27 March 1986, I discovered a pair of nesting Black-shouldered Kites in the north
end of Water Conservation Area 3A (CA3A), Broward County. Two more nesting pairs
were located in the same vicinity on 5 and 30 April. By mid-June seven kites had fledged
from these three nests. A photograph of one of these nestlings will be deposited in the
Florida State Museum.

All three nests consisted of small twigs and were built in living wax myrtles {Myrica
cerifera). The first nest was located 3.08 m high in a 3.50 m tall wax myrtle. The nest was
constructed of sticks and was 30-35 cm in diameter and 7-10 cm deep. On 27 March 1986
the water level near this nest was at natural ground level and continually decreased during
the nesting period. During the first inspection (2 April) the nest contained three young and
one egg. By 14 April there were two young and one egg. On 19 April three young kites
were in the nest. By 26 April one nestling remained; on 28 April it fledged. On 5 May five
kites were observed in the vicinity of the nest. These were assumed to be the three
immatures and two adults from this nest. The last egg did not hatch.

The second and third nests were 4.0 and 1.9 km east of the first nest. They also were
constructed of sticks in wax myrtles; 4.9 and 3.2 m above the ground, respectively. The
second nest was 30.5-38.1 cm in diameter; the third was more oblong, 50.8 cm long and
30.5 cm wide. On 12 April the second nest contained one egg. Two young were seen in this
nest on 16 May. On 24 May each adult was seen flying to the nest, and on 26 May both
adults were seen in the area. A grackle ( Quiscalus sp.) was seen on the nest tree on 30
May; two adult kites were seen 0.8 km from the nest. On 31 May no kites were seen in
this area. One adult was seen south of the nest on 1 June, and on 2 June it was found to
be abandoned. The third nest was located on 30 April; it contained at least four eggs on 1
May. On 15 May it contained five nestlings, three birds in the natal down stage and two
in the early stages of juvenal plummage. On 28 May at least one (possibly two) of the five
nestlings was on the verge of leaving the nest. Only one nestling was still in the natal down
stage, and I believe it died sometime later. On 4 June a nestling was perched on a dead
branch above the nest, and two more (in juvenal plummage) remained in the nest. On the
final visit to this nest (10 June), one nestling was seen. Five other kites were seen perching
and flying in the vicinity of the nest. Kites were seen in the area until mid-July.

Habitat in the vicinity of these nests is generally described as open and brushy. As the
ground elevation increases in the north end of CA3A, there is a transition from a typical
Everglades sawgrass ( Cladium jamaicensis)/ tree island association to a wax myrtle/salt
bush ( Baccharis halimifolia)/s2LWgrass association.

Hair samples from prey remains in the first nest were later identified as hispid cotton
rat ( Sigmodon hispidus) and rabbit ( Sylvilagus spp.). My observations indicate that marsh

106

Notes

107

rabbits (S. palustris ) and cotton rats are common in CASA. Brown and Amadon (1968)
state that Black-shouldered Kites select areas of heavy rodent concentration in which to
nest.

Because there were three nests, I believe one or more of these breeding pairs may have
nested here in the recent past. Anticipating their return I began to “glass” the area period-
ically with a spotting scope. As of 25 January 1987 I had not seen any returning kites. On
20 and 23 February Lance McLellan and myself observed a kite perched on dead wax
myrtles separated by approximately 2,0 1cm. Because only one kite was seen on each day,
I believe it was the first potential nesting bird of the season. Brown and Amadon (1968)
reported that in California the onset of the breeding season is shown when a male selects
a perch where he sits daily at certain hours. On 9 and 20 April I did not see any kites in
the area.

I thank the following people for assisting me in field work, writing or editing: John Ault,
Bill Bolte, Mike Brown, Jim Cox, George Eddie, Wally George, Vic Heller, Howard Lan-
gridge, Lance McLellan, Brian Millsap, Grace Neumann, Mark Robson, James Rodgers,
Eddie Rosenberg, Henry Stevenson, and Roy Teitelbaum. The Florida Game and Fresh
Water Fish Commission supported this work.

Literature Cited

Atherton, B. H., and L. S. Atherton. 1985. Florida region. Amer. Birds 39: 43.
Bolte, W. 1986. Christmas bird count. Amer. Birds 40: 764.

Brown, L., and D. Amadon. 1968. Eagles, hawks and falcons of the world. Vol. 1. New
York, New York: McGraw-Hill Book Co.

Gatz, T. A., D. L. Base, A. S. Mgorhouse, J. D. Tyler, and B. C. Thompson. 1986.
Status of the Black-shouldered Kite in the southwest region. Phoenix, Arizona: U. S.
Department of Interior, U. S. Bureau of Reclamation Rept.

Hoffman, W. 1985. Florida region. Amer. Birds 39: 159.

Kale, H. W., II. 1974. The status of the White-tailed Kite in Florida. Fla. Field Nat. 2:
4-7.

Sprunt, A., Jr. 1952. Florida bird life. New York, New York: Coward-MeCann.

To ups, J. A., J. A. Jackson, and E. Johnson. 1985. Black-shouldered Kite: range
expansion into Mississippi. Amer. Birds 39: 865-867,

Robert L. King, Florida Game and Fresh Water Fish Commission, P. O. Box 840337,
Pembroke Pines, Florida 33084.

Florida Field Naturalist 15: 106-107, 1987.

Great Blue Heron eats gray squirrel.-— -The Great Blue Heron ( Ardea herodias ) is
known to capture and eat a wide variety of prey including fish, reptiles, amphibians,
insects, birds and rodents (R. S. Palmer 1962, Handbook of North American birds, Vol. I,
New Haven, Connecticut: Yale Univ. Press). However, we have found no reference in the
literature to the Great Blue Heron killing and eating adult gray squirrels ( Sciurus
carolinemis).

On 31 March 1987, Brooks heard the scream of a gray squirrel in her backyard, which
is on a brackish lagoon in Ponte Vedra Beach, St. Johns County, Florida. When she looked

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FLORIDA FIELD NATURALIST

out, she saw a Great Blue Heron holding the struggling adult squirrel by the head. At her
approach, the heron flew, carrying the squirrel to the lagoon where it perched on rocks in
the water. The heron alternately submerged the squirrel, then took it out of the water and
vigorously shook it. After about 5 min of alternately shaking and wetting, the heron swal-
lowed the squirrel head first. Apparently the squirrel was still barely alive at this point,
though greatly weakened. After swallowing the animal and drinking a quantity of water,
the heron flew away. Whether the bird was deliberately trying to drown the squirrel by
wetting it or merely lubricating it to ease swallowing is not known.

Great Blue Herons have been known to choke on prey too large to swallow (Palmer
1962). Weights of adult gray squirrels range from 338 to 750 g (J. A. Chapman and G. A.
Feldhamer 1982, Wild mammals of North America, Baltimore, Maryland: Johns Hopkins
Univ.), but the smaller individuals are found in the southern parts of the species’ range.

Since girth is probably more critical than weight as a limitation on prey size for any
predator that swallows prey whole, we measured the girth of a sample of intact road-killed
gray squirrels (n=3) in Duval Co., Florida in June 1987. Maximum girth was surprisingly
uniform at about 15.25 cm, measured at 3 places along the body (forequarters, middle,
hindquarters).

Since Great Blue Herons have been observed swallowing prey as large as an Anhinga
(. Anhinga anhinga ) (C. L. Abercrombie, pers. comm.), gray squirrels are probably well
below the maximum size prey for this predator. However, the handling behavior of the
heron was not appropriate to drown the squirrel, which would tend to indicate that the
taking of air breathing animals by the Florida population of this heron is purely opportunis-
tic and without evolved behavior to maximize success.

We thank James A. Rodgers, Jr. and an anonymous referee for helpful comments on
the manuscript. — Jeanette Brooks, 8 Pablo Road, P. 0. Box 561, Ponte Vedra Beach,
Florida 32082 and Robert W. Loftin, Dept, of History and Philosophy, University of North
Florida, 4567 St. Johns Bluff Road, S., Jacksonville, Florida 32216.

Florida Field Naturalist 15: 107-108, 1987.

REVIEWS

The fall of a sparrow. — Salim Ali. 1985. Oxford, Oxford Univ. Press. 265 pp. + 71
black and white photographs. Rs.110 ($16.95).- — In writing this review, I am at once hesit-
ant because I know how little Salim Ali enjoys public attention. In his own words “it took
considerable persuasion from friends and ‘fans’ to evoke in me the courage to write an
autobiography ...” which would let “ curious (my italics) people know how and whence I
contracted the germs of ornithology . . . .” So, at the risk of incurring his displeasure, I
am going to recommend this autobiography to anyone with a love of nature, a sense of
humor and a curiosity about the progress of ornithology in India. This book has humor in
good measure while it tells the extraordinary story of a man who followed his ornithological
dream with scant regard for material gain at a time when ornithology was little known and
scarcely regarded as a “respectable” profession among his peers. Consequently, Salim Ali
is one of those rare individuals who has lived life to the fullest and still continues to do so.

Scientific ornithology in India was initiated and pursued by the British, mostly by
officers in Her Majesty’s service. Originating as a “hobby” for many officers stationed in
remote areas, it developed into a serious occupation in such pioneers as E. C. Stuart Baker
who authored the second edition of the volumes on birds in the “Fauna of British India”
series, and Hugh Whistler. Then, into this British dominated sphere came Salim Ali. He
had his appetite for ornithology whetted by a compulsory and nearly continuous stay in the

Reviews

109

Tavoy district of Burma from 1914 to 1923 where he was attending to a family business.
He went to Berlin to train under Erwin Stresemann whom he regards as his “guru” and
came back equipped to make his own important scientific contributions to Indian ornithol-
ogy.

Salim All tells the story of Ms association with the Bombay Natural History Society
(BNHS), the foremost organization of its kind in India today. He traces this relationship
from the time he was directed to its collections in the offices of Phipson and Co. , Wine
Merchants (!) after the “fall of the sparrow” to the present when he is president of the
BNHS. He was twelve years old when the sparrow fell. He tells of Ms breaking into a
virtually all-British stronghold, rarely resisting a chuckle at the sahibs.

He has interesting accounts of the ornithological surveys he conducted in association
with the BNHS, in various Princely States of India, under the patronage of the Maharajahs.
His sense of fun, adventure, capacity for hard work and striving for perfection come
through at all times. Those surveys were the basis for several books on regional ornithology
published by Oxford University Press, like “Birds of Kerala” and the “Field Guide to the
Birds of the Eastern Himalayas.” These culminated in his magnum, opus, “The Handbook
of the Birds of India and Pakistan” (in ten volumes), written in collaboration with S. Dillon
Ripley. The Handbook was written to fully update Stuart Baker's work in the “Fauna of
British India” series and to include original information on the ecology of the species. He
also wrote a popular field guide, “The Book of Indian Birds,” which is widely used today.
He writes only briefly about his fascinating seminal study on the breeding biology of baya
weaver birds. It is obvious, however, that Salim Ali enjoys behavior and ecology much
more than systematics.

He writes of his friendship (to cite only a few) with Hugh Whistler who gave him much
useful practical advice in Ms salad ornithological days; with Richard Meinertzhagen,
D.S.O., the intrepid Colonel of “A Kenya Diary” fame with whom he expeditioned to
Afghanistan and shared other good times; with Loke Wan Tho, the “quiet and scholastic”
businessman with an “eye for beauty” who became a world renowned bird photographer
during his exile in India from Singapore; with J. B. S. Haldane and with Dillon Ripley with
whom he still shares an uncommon rapport.

He writes with deep affection about his interesting and large family, some of whom
were deeply committed to social or political causes. Though Salim Ali is himself not political,
he obviously has strong feelings about the role of the British in India and the role of Indians
themselves. These feelings flash through occasionally.

Salim Ali, unlike virtually all of us, was present at a time when Indian wildlife was
“plentiful” and Indian forests were relatively well preserved. From Ms book one gets the
flavor of what it must have been like then. The last tiger on the outskirts of Bombay was
shot in 1929! Days and times, a whole period gone by. One detects regret and nostalgia in
the book but only fleetingly for the “young” man of ninety years is optimistically passionate
about conserving what is left. As a nominated member of the Indian Rajya Sabha (the
country’s highest governing council), Salim Ali is actively fighting today for his own special
part of the planet.

The book has many events and personalities condensed into its pages, snatches from a
much larger wealth of experiences. However, it captures the essence of a great man whose
example is worth savoring. The seventy-one excellent photographs are of memorable times
and places (Editor’s note: Salim Ali passed away on June 20, 1987 after a long illness which
he fought with tenacity. He will be missed by fellow ornithologists, conservationists, and
friends throughout the world.).— Renee M. Borges, Department of Biology, University of
Miami, Coral Gables, Florida 33124 and 104/C Aradhana, G. D. Ambekar Road, Naigaum,
Bombay 400 014, India.

Florida Field Naturalist 15: 103-109, 1987.

110

FLORIDA FIELD NATURALIST

Birder’s life list & diary. — Ron and Betty Dietert, revised and edited by S. C. Sibley.
1986. Cornell Laboratory of Ornithology, Ithaca, New York. 213 pp. Soft covers, spiral
bound; $6.95.-— This book, first published by the Dieterts in 1959, provides birders a means
to record the field notes of their first sightings of North American and Hawaiian birds.
Steven C. Sibley revised and updated this edition to reflect changes in names and classifi-
cations as introduced in the 6th edition of the “Check-list of North American birds” (Amer-
ican Ornithologists’ Union 1983, Lawrence, Kansas: Allen Press) and the “Thirty-fifth sup-
plement to the A.O.U. check-list of North American birds” (1985, Auk 102: 680-686).

The Species Listing section presents in taxonomic order 690 species of birds regularly
occurring in North America north of Mexico plus 22 birds, formerly given full species
status, now considered subspecies, color forms or color morphs. Space is available for
recording date, location and field notes for each entry. English and scientific names are
given for each species. Species are grouped by order. Blank spaces are provided for adding
accidentals at the end of most orders and, in the case of some of the larger orders (e.g.,
Charadriiformes and Passeriformes), within the order.

Appendix A lists 72 species of birds which occur regularly in the Hawaiian Islands.
Again, space is provided for recording information on sightings. Appendix B lists 156
species that the A.O.U. recognizes as occurring accidentally in North America. Five small
check spaces are provided after each entry for recording a sighting or indicating a page
reference number. Appendix C is a blank list of 828 spaces for recording sightings in the
order in which they are made. Finally, the Index is an alphabetical list of birds by English
names with references to page numbers in the Species Listing section or in Appendices A
and B. Twelve check spaces are provided for each species.

The “Birder’s life list & diary” is easy to use and a versatile aid for organizing first
sightings. These may be recorded in taxonomic, alphabetic or temporal order. Ample space
is available for entering information in the first two sections. A Quick Finder Guide is
provided to facilitate location of orders or certain groupings within orders in the Species
Listing section.

The soft cover of the diary may not prove durable for field use. Within the Species
Listing section the orders could well have been subdivided into families and, where appro-
priate, into subfamilies, particularly within the Passeriformes. Such further division would
indicate relationships within orders and within mega-families such as the Emberizidae.
Additional blank spaces for recording sightings of accidental species would be useful at the
end of the family or subfamily divisions; here they would be more meaningful and logical.
It would have been useful if Appendix A, the listing of Hawaiian birds, had been subdivided
into orders, families and subfamilies. There might have been some justification for including
the accidentals listed in Appendix C within the main body of the diary. This would have
enabled the user to see the relationship of accidentals to regularly occurring North Amer-
ican birds and would have facilitated the recording of data for these species.

Intermediate and advanced birders, who have already recorded data on first sightings
in personal notebooks or other record forms, might find transcribing this information into
the the format of the diary laborious. Beginning and early intermediate birders, however,
should find this book very worthwhile. The diary provides a format for recording and
organizing information on species; it can be maintained as skills improve and life lists
lengthen. As beginners become advanced birders, they will have a continuing record of
memories and increasing proficiency. — Mary Catherine Wheeler, 11700 SW 104 Avenue,
Miami, Florida 33176.

Florida Field Naturalist 15: 110, 1987.

Reports

111

EDITORIAL

Acknowledgments. — This concludes my first volume as editor of the Florida Field
Naturalist. Both Jim Kushlan and Fred Lohrer were always willing to answer my questions
or requests for assistance. I appreciate the help of the Associate Editors, especially Richard
Paul and Oscar Owre. I also thank the officers and members of the Florida Ornithological
Society for support of the journal and the E. 0. Painter Co. for their fine work. I appreciate
the encouragement and support from the Florida Game and Fresh Water Fish Commission.
The following individuals accepted the arduous challenge of reviewing manuscripts during
this volume: L. Atherton, T. Bancroft, T. Below, R. Bennett, J. Brady, D. Buden, J.
Burger, M. Callopy, D. Carlock, S. Clark, J. Cox, T. Edwards, D. Freeman, S. Furniss,
J. Gore, L. Banners, W. Hardy, L. Harris, J. Iverson, D. Jackson, F. James, F. Johnson,
H. Kale, L. Kilham, W. Koenig, H. Langridge, J. Layne, P. Moler, J. Ogden, T. O’Meara,
S. Patton, R. Paul, A. Poole, G. Powell, W. Robertson, D. Runde, H. Stevenson, P. Sykes,
D. White, and J. Wiley.

REPORTS

Summary of the 1987 spring meeting.— The spring meeting of the Florida Ornitholog-
ical Society was held at the Episcopal Camp and Conference Center near Live Oak, Florida.
Pete Southall and the Four Rivers Audubon Society were our hosts from 5-7 June. Presi-
dent Bob Brown thanked the local committee for their efforts and announced that the fall
meeting will be in Clearwater from 2-4 October 1987.

The meeting was designed as a blockbusting party for the Breeding Bird Atlas Project.
An organizational meeting was held on Friday evening and blockbusting parties went out
on Saturday and Sunday mornings. A brief roundup of the first day’s results was held in
place of the paper session on Saturday afternoon.

No skin quiz or song quiz were prepared. The Atlas staff, however, came through with
the prizes. Joe Ondrejko of Key West received a copy of Jim Lane’s “Birder’s Guide to
Florida” for having travelled the farthest distance. Pete Southall and Brenda Rhodes were
given BBA T-shirts for organizing the blockbusting. Richard Slater received a copy of the
newly revised National Geographic field guide for helping to confirm the most breeding
bird species. The Atlas staff presented a framed Ray Harms print' to Buck Cooper for
“Most Valuable Coordinator.”

Two slide shows on the Suwannee River were presented during the Initial Flocking on
Friday evening. The banquet speaker was Dr. Bob Loftin, who presented a program on
“Birds of the Arctic Tundra,” where he participated in a research program.

During the membership meeting, new officers were elected. Their names appear else-
where in this issue. It was announced that this year’s Helen G. and Allan D. Cruickshank
Research Award will go to Bonnie J. Ploger of the University of Florida for her dissertation
work on “Do parent Cattle Egrets manipulate hatch intervals?”— Bruce Neville, 8221 SW
72 Avenue, Apt. 273, Miami, Florida 33143.

112

FLORIDA FIELD NATURALIST

FLORIDA ORNITHOLOGICAL SOCIETY, INC.
TREASURER S REPORT 1986

TOTAL FUND BALANCE, Cash in banks at year-end

1985

1986

Checking accounts

$9,368.76

$10,728.16

Research certificate, #1

1,986.85

2,227.55

Research certificate, #2

1,400.00

1,520.77

Research certificate, #3

2,000.00

Endowment certificate

3,234.47

3,626.30

$15,990.08

$20,102.78

1986 CASH RECEIPTS AND DISBURSEMENTS
TOTAL FUND BALANCE, 1 January 1986 $15,990.08

Cash receipts Cash disbursements

Membership dues ....

$6,843.00

Membership ...........

.. $629.87

Meetings

3,294.70

Meetings

.. 2,641.14

FFN

867.50

FFN

.. 5,295.17

Special Publ. Fund ..

188.00

Special Publ. Fund ..

39.15

Special Projects ......

31.50

Special Projects

50.00

Research Fund .......

1,312.50

Research Fund

300.00

Interest earned

1,472.25

Operating

497.44

$14,009.45

Newsletter

443.98

$9,896.75

TOTAL FUND BALANCE, 31 December

1986

$20,102.78

ANALYSIS OF FUND BALANCE

$20,102.78

Less 1987 dues paid during 1986

1,743.00

Less balances in special funds

16,877.34

Research Fund

$6,499.63

Special Publ. Fund

4,135.53

FFN Fund

2,615.88

Endowment Fund

3,626.30

$16,877.34

ACTUAL GENERAL FUND BALANCE ,

, 31 December 1986 ......

............. $1,482.44

Caroline H. Coleman, Treasurer, 1701 NW 24th Street, Gainesville, Florida 32605.

Florida Field Naturalist

ISSN 0738-999X

PUBLISHED BY THE FLORIDA ORNITHOLOGICAL SOCIETY

Editor: James A. Rodgers, Jr., Wildlife Research Laboratory, 4005 South Main Street,
Gainesville, Florida 32601.

Associate Editor (for bird distribution): Howard P. Langridge, 1421 West Ocean Av-
enue, Lantana, Florida 33462.

Associate Editor (for reviews): Oscar T. Owre, Department of Biology, University of
Miami, Coral Gables, Florida 33124.

Associate Editor (for technical papers): Richard T. Paul, National Audubon Society,
410 Ware Blvd., Suite 500, Tampa, Florida 33619.

Special Editor (for periodical literature): Fred E. Lohrer, Archbold Biological Station,
P. 0. Box 2057, Lake Placid, Florida 33852.

Editorial Advisory Board: Oscar T. Owre; G. Thomas Bancroft; Henry M.
Stevenson; and Fred E. Lohrer (Chairman).

FOS Bird Records Committee: Noel Wamer; Larry Hopkins; Rebecca L. Payne;
Oron L. Bass; and Helen Dowling (Secretary), 203 Toumblin Cling Rd., Ft.
Pierce, Florida 33482.

Editor of Special Publications: John William Hardy, Florida State Museum, Gaines-
ville, Florida 32611.

Editor of the Ornithological Newsletter: Herbert W. Kale, II, Florida Audubon So-
ciety, 1101 Audubon Way, Maitland, Florida 32751.

INFORMATION FOR CONTRIBUTORS

The Florida Field Naturalist is a fully refereed journal emphasizing biological field
studies and observations of vertebrates, especially birds, in and near Florida and the
nearby West Indies. It welcomes submission of manuscripts containing new information
from these areas. Please consult recent issues for style, and Vol. 15, No. 1 for detailed
information. Submit manuscripts for consideration to the editor James A. Rodgers. Mono-
graph-length manuscripts may be submitted for consideration to the Editor of Special
Publications John William Hardy. Send books and other materials for review to Associate
Editor Oscar T. Owre. Send copies of recent literature on Florida birds to Special Editor
Fred E. Lohrer. For preliminary assistance regarding submission of manuscripts dealing
with bird distribution and rarities contact Associate Editor Howard P. Langridge. Reports
of rare birds in Florida should also be submitted to the FOS Records Committee Secretary
Dorothy Freeman. For preliminary assistance regarding submission of scientific, technical,
or behavioral contributions contact Associate Editor Richard T. Paul.

SMITHSONIAN LIBRARIES

III II 111 1 11

111 II II

3 9088 0192

>1 5159

Florida Field Naturalist

PUBLISHED BY THE FLORIDA ORNITHOLOGICAL SOCIETY

Vol. 15, No. 4 November 1987 Pages 85-112

CONTENTS

ARTICLE

Summer concentration of American Swallow-tailed Kites at Lake Okeechobee,

Florida, with comments on post-breeding movements .. Brian A. Millsap 85-92

Roosting behavior of the Yellow-shouldered Blackbird

William Post and Kathleen W. Post 93-105

NOTES

Successful nesting of Black-shouldered Kites in the Everglades of

Broward County, Florida Robert L. King 106-107

Great Blue Heron eats gray squirrel . Jeanette Brooks and Robert W. Loftin 107-108

REVIEW

The fall of a sparrow Renee M. Borges 108-109

Birder’s life list & diary Mary Catherine Wheeler 110

EDITORIAL

Acknowledgments James A. Rodgers, Jr. Ill

REPORTS

Summary of the 1987 spring meeting Bruce Neville 111

Florida Ornithological Society, Inc. Treasurer’s Report 1986

Caroline H. Coleman

112