Table Of ContentSHORT COMMUNICATIONS 101
fledging associations of adults and offspring LITERATURE CITED
also have been documented in other brood-
parasitic taxa, such as the Brown-headed Daviecshe,atNs.. TB..&20A0.0D..CPuocyksoero,s,Locnodwobni,rdsU,nitaendd Koitnhge-r
Cowbird (Molothrus ater\ Hahn and Fleischer dom.
1995). Indeed, previous reports have docu- Friedmann, H. 1968. The evolutionary history of the
mented male Klaas’s and Diederik cuckoos genus Chrysococcyx. U.S. National Museum Bul-
provisioning both pre-volant young and mul- letin, no. 265, Smithsonian Institution, Washing-
tiple fledglings (Moreau 1944, Friedmann ton, D.C.
1968, Lorenzana and Sealy 1998), thus ex- Hahn, D. C. and R. C. Fleischer. 1995. DNA finger-
print similarity between female and juvenile
cluding misidentification of adult females as
We Brown-headedCowbirdstrappedtogether. Animal
sufficient explanation for this behavior. Behaviour 49:1577-1580.
speculate that not only are females sometimes Irwin, M. P. S. 1988. Order Cuculiformes. Pages 58-
misidentified as fledglings, but perhaps older 104 in Birds of Africa, vol. Ill (C. H. Fry, S.
fledglings being provisioned by males are Keith, and E. K. Urban, Eds.). Academic Press,
sometimes mistaken for females being court- London, United Kingdom.
ed. If earlier reports were correct and provi- Iverson, E. and B. Hill. 1983. DiederikCuckoofeeds
fledgling of same species. Bee-eater 34:47.
tsiivoenliyngcoomfmfolendgilnintghsebAyfraidcualnt Cmharlyessociosccreylxa,- Lorepnazraasniat,esJ.feCe.dainngdnSe.stGl.inSgesalayn.d 1fl9e9d8g.liAndgusltofbrthoeoidr
it raises interesting questions about the genetic own species: a review. Journal ofField Ornithol-
relatedness of the interacting individuals and ogy 69:364-375.
their underlying social system. Millar, H. M. 1926. Golden Cuckoo, C. cupilus.
South AfricanJournalofNatural History6:28-29.
ACKNOWLEDGMENTS Moreau, R. E. 1944. Food-bringing by African
Bronze Cuckoos. Ibis 86:98-100.
We thank M. Muchai and the many additional staff Rowan, M. K. 1983. The doves, parrots, louries, and
members of the Department of Ornithology, National cuckoos of Southern Africa. David Philip, Cape
Museums of Kenya who have greatly facilitated our Town, South Africa.
field research in their country. We similarly acknowl- Sibley, C. G. and B. L. Monroe. 1990. Distribution
edge the Kenya Wildlife Service and the Mpala Re- and taxonomy ofbirds ofthe world. Yale Univer-
search Centre forallowing us toconductthis research. sity Press, New Haven, Connecticut.
The Wilson Journal ofOrnithology 118(1):101-104, 2006
Widespread Cannibalism by Fledglings in a Nesting Colony of
Black-crowned Night-Herons
Christina Riehl12
—
ABSTRACT. I studied the diet and foraging be- enging. Isolated incidents of cannibalism among
havioroffledgling Black-crowned Night-Herons(Nyc- Black-crowned Night-Herons have been reported pre-
ticorax nycticorax) in a mixed-species nesting colony viously, but not on a colony-wide scale. Received 2
of Black-crowned Night-Herons and Snowy Egrets December2004, accepted 19 September2005.
(Egretta thula) in New Orleans, Louisiana. In 1 of 5
years, cannibalism of nestlings that had fallen or
climbed out of nests was common, accounting for 66
of94(70.2%)preyitemstakenbyfledglings.Juveniles Many researchers have studied the diets of
took youngerconspecifics by both predation and scav- adult and nestling Black-crowned Night-Her-
ons (Nycticorax nycticorax; Bent 1926, Palm-
1 5500 Camp St., New Orleans, LA 70115, USA. er 1962, Wolford and Boag 1971), but there
2Current address: Dept, of Ecology and Evolution- are few data on the diet and foraging behavior
ary Biology, Princeton Univ., Princeton, NJ 08544, of juveniles immediately after leaving the
USA; e-mail: [email protected] nest. Here, I provide the first report of wide-
n n
102 THE WILSON JOURNAL OF ORNITHOLOGY • Vol. 1/8, No. 1, March 2006
spread cannibalism and scavenging ofconspe- er fledglings (see Noble et al. 1938 for a full
cifics among fledglings in a nesting colony of description of territoriality in juvenile night-
Black-crowned Night-Herons. herons). Fledglings rarely ventured into the
water to hunt; rather, they spent most of their
METHODS
time foraging on the ground under active
From 1 February to 18 July 2000, I moni- nests. Of 94 prey items that I saw juvenile
tored a colony of Black-crowned Night-Her- night-herons consume, 66 (70.2%) were youn-
ons on Ochsner Island, Audubon Park, New ger fledgling or nestling night-herons. I ob-
Orleans, Fouisiana (29° 56' N, 90° 8' W) as served juveniles feeding on both chicks that
=
part of a long-term (1997-2001) study on re- they killed (n 20) and chicks that were al-
productive success. Ochsner Island is a small ready dead when I began observations ( =
(600 m2) island in a man-made lagoon; the 46). Other prey items included fish (10.6%),
distance between the island and the shore of frogs (8.5%), brown rats (Rattus norvegicus\
the mainland is approximately 6 m. The is- 4.3%), carrion dropped from active nests
land’s vegetation is dominated by Chinese tal- (3.2%), Wood Duck chicks (Aix sponsa;
lowtree (Sapium sebiferum) and live oak 2.1%), and a dead Snowy Egret nestling
(Quercus spp.). In 2000, 143 pairs of Black- (1.1%).
crowned Night-Herons and 10 pairs ofSnowy Fledglings did not prey on chicks in nests
Egrets (Egretta thula) nested on the island. or chicks perched in vegetation; they limited
Nest height ranged from 1 to 7 m above their attacks to nestlings on the ground that
ground. I recorded the diet and foraging be- had fallen or climbed out of nests. Adults de-
havior ofapproximately 70juvenile night-her- fended chicks in nests, but I never observed
ons from fledging until the end ofthe breeding adults interfering with fledglings that were
season, when the members of the nesting col- preying on chicks on the ground. Since older
ony dispersed. Night-herons were considered night-heron nestlings often left the nest to
to have fledged when they left the nest per- perch on nearby vegetation before fledging
manently and were no longer fed by adults, at permanently, it was not always clear whether
which point most were capable of clumsy victims were nestlings that had fallen from
flight. Prey items were identified by direct ob- nests or younger fledglings that had just left
servation of foraging night-herons. Observa- the nest. It is probable, however, that preda-
tions were made from the mainland, from tion by fledgling night-herons increased mor-
which approximately half of the nests in the tality rates of chicks that had climbed out of
colony could be observed. observed foraging the nest and would have otherwise been able
I
juveniles for 546 hr. to climb to safety. Older nestlings in low nests
(<1.5 m above ground) often climbed out of
RESUFTS
the nest onto the ground before fledging, and
Juvenile Black-crowned Night-Herons were were therefore more vulnerable to attacks than
fed by parents until 45 ± 3 (SD) days after nestlings in high nests.
hatching ( = 23). However, juveniles were Small, weak, and moribund chicks were at-
able to climb out of the nest and onto sur- tacked more frequently than healthy-looking
rounding vegetation as early as 30 days after nestlings near the age of fledging. The victims
hatching, returning to the nest when a parent were approximately 50-70% of the size of
approached with food. At 35 days, juveniles fledglings and appeared difficult to kill and
readily left their nests, often climbing out of consume. Fledglings killed younger conspe-
the nest to solicit food from a nearby parent cifics by striking them with their bills for up
or unrelated adult night-heron. to 1 hr or more, and then consumed them by
Juveniles remained on the island for 1—3 repeatedly striking the carcasses and labori-
weeks after leaving the nest permanently, ously tugging small pieces ofmeat from them.
forming small groups of one to four individ- Older fledglings were particularly skilled at
uals from the same nest, or neighboring nests. preying on nestlings and appeared to focus
Each group or lone individual occupied a their foraging attempts on nestlings to the ex-
small (7—9 m2) territory on the ground and clusion of other prey. When a fledgling found
defended the areafrom passing adults and oth- an undefended nestling and began to attack it.
-
SHORT COMMUNICATIONS 103
other fledglings usually came to fight over the found that juveniles sometimes climbed back
victim. In one case, I observed five fledglings to the nest in the first 2-3 days after fledging,
attack and consume a 15-day-old nestling that and were usually fed by the parents. After 3
had fallen from its nest. days post-fledging, fledglings on the ground
often grabbed the bills of passing adults in an
DISCUSSION
attempt to stimulate them to regurgitate food,
Black-crowned Night-Herons are among but were almost always unsuccessful.
the most opportunistic ofNorth American her- Fledglings also seemed unable to fish effi-
ons. They employ several different foraging ciently in the deep water surrounding the is-
behaviors (Kushlan 1976) and consume a land, at least for the first 7 or 8 days after
wide variety ofprey, including fish, mollusks, fledging. I frequently observed fledglings in
insects, reptiles, amphibians, rodents, birds, the water striking at floating sticks and pieces
eggs, carrion, refuse, and plants (Hancock and of leaves, but they rarely captured live prey.
Kushlan 1984, Davis 1993). Night-herons will Fledglings occasionally picked up prey
alter their foraging methods to concentrate on dropped by nestlings in active nests; on one
locally abundant resources, including mice occasion, a fledgling climbed into a low nest
(Allen and Mangels 1940), fish (Spanier and pulled a fish from the bill ofthe fledgling
1980), and amphibians (Wetmore 1920). They to which it hadjust been delivered. Adults, by
have also been reported to systematically ex- contrast, were never observed feeding on dead
ploit rookeries of other colonially nesting nestlings or other carrion, suggesting that they
birds, including Common Terns {Sterna hirun- were more skilled at catching higher-quality,
do\ Marshall 1942, Collins 1970, Shealer and
live prey.
Kress 1991) and Franklin’s Gulls {Larus pi- Although spent similar amounts of time
pixcan\ Wolford and Boag 1971). Kale (1965) observing theI same rookery each year (1997-
reported an instance of adult night-herons in 2001), cannibalism among Black-crowned
a colony preying opportunistically on White
Night-Heron fledglings was prevalent only in
dIbeiasa(lEbuad)occhiimcukss farlobumst)heansdamGeremaitxeEdg-rseptec(Aiers 2000. I observed night-heron fledglings feed-
ing on dead night-heron and egret chicks only
rookery, noting that ibis and egret chicks from
twice in 1998 and once in 2001. The species
neighboring nests constituted a major food
composition of the nesting colony was fairly
source for night-heron chicks. Published re-
constant across years, comprising 120-150
ports of night-herons feeding on conspecifics,
pairs of Black-crowned Night-Herons and 5—
however, are limited to Wolford and Boag’s
10 pairs of Great Egrets and Snowy Egrets;
(1971) report of a night-heron nestling that
was regurgitated by anothernestling. Williams thus, the level of competition for food among
fledglings on the island should not have been
and Nicholson (1977) reported a suspected in-
stance of brood reduction in the Black- elevated in 2000. In other years, fledgling di-
crowned Night-Heron, but did not find evi- ets were dominated by fish and frogs. How-
dence of cannibalism. ever, it is difficult to compare prey composi-
There is virtually no information on the for- tion across years because I observed far fewer
aging behavior of night-heron fledglings dur- prey captures in other years, possibly because
ing t—he period immediately afterthey leave the juvenile Black-crowned Night-Herons may
nest after the adults have stopped feeding forage mostly at night.
them but before they become adept atcatching It is possible that cannibalism rates were
their own prey. Lorenz (1938) and Palmer exceptionally high in 2000 because local
(1962) reported that fledglings move through shortages of fish or other live prey forced
the colony and are able to beg food from any fledglings to seek alternate food resources, but
adult; however, Finley (1906) and Noble et al. I was unable to document such a shortage. A
(1938) found that adults do not feedjuveniles food shortage would have affected the diet
on the ground. Data on the composition of and foraging patterns of fledglings more than
fledgling diet are scarce, possibly because re- adults and nestlings, since adults often left the
cently fledged juveniles may forage at night nesting colony to forage while fledglings re-
(Rockwell 1910, Davis 1993). In this study, I mained on the island.
3
104 THE WILSON JOURNAL OF ORNITHOLOGY • Vol. 118, No. 1, March 2006
ACKNOWLEDGMENTS
of the International Ornithological Congress 8:
207-218.
I am grateful to W. E. Davis, Jr., J. A. Kushlan, and Marshall, N. 1942. Night desertion by nesting Com-
an anonymous reviewerfortheirhelpful commentson mon Terns. Wilson Bulletin 54:27-31.
the manuscript. Noble, G. K., M. Wurm, and A. Schmidt. 1938. So-
cial behavior of the Black-crowned Night Heron.
LITERATURE CITED
Auk 55:7-40.
Allen, R. P. and F. P. Mangels. 1940. Studies ofthe Palmer, R. S. 1962. Handbook of North American
nesting behaviorofthe Black-crowned NightHer- birds, vol. I: loons through flamingos. Yale Uni-
on. Proceedings of the Linnean Society of New versity Press, New Haven, Connecticut.
York 50-51:1-28. Rockwell, R. B. 1910. Some Colorado night heron
Bent, A. C. 1926. Life histories of North American notes. Condor 12:113-121.
marsh birds. U.S. National Museum Bulletin, no. Shealer, D. A. and S. W. Kress. 1991. Nocturnal
135, Smithsonian Institution, Washington, D.C. abandonment response to Black-crowned Night-
Collins, C. T. 1970. The Black-crowned Night Heron Heron disturbance in aCommon Terncolony. Co-
as a predator oftern chicks. Auk 87:584-586. lonial Waterbirds 14:51-56.
Davis, W. E., Jr. 1993. Black-crowned Night-Heron Spanier, E. 1980. The use of distress calls to rep2el
(Nycticorax nycticorax). The Birds of North night herons (Nycticorax nycticorax) from fish
America, no. 74. ponds. Journal of Applied Ecology 17:287-294.
Finley, W. L. 1906. Herons athome. Condor8:35-40. Wetmore, A. 1920. Observations on the habits of
Hancock, J. and J. A. Kushlan. 1984. The herons birds atLake Burford, New Mexico. Auk37:393-
handbook. Harper and Row, New York. 412.
Kale, H. W., II. 1965. Nestling predation by herons in Williams, M. D. and C. P. Nicholson. 1977. Obser-
a Georgia heronry. Oriole 30(March):69-70. vations at a Black-crowned Night-Heron nesting
Kushlan, J. A. 1976. Feeding behavior of North colony. Migrant 48:1-7.
American herons. Auk 93:86-94. Wolford, J. W. and D. A. Boag. 1971. Food habits
Lorenz, K. 1938. A contribution to the comparative of Black-crowned Night Herons in southern Al-
sociology of colonial-nesting birds. Proceedings berta. Auk 88:435-437.
The Wilson Journal ofOrnithology 1 18(1):104-106, 2006
First Report of Black Terns Breeding on a Coastal Barrier Island
Shawn R. Craik,1 Rodger D. Titman,1 Amelie Rousseau,1 and Michael J. Richardson
—
ABSTRACT. Black Terns (Chlidonias niger suri- neitherchicksurvivedbeyond4days.Received15De-
namensis) breed locally in freshwater wetlands across cember 2004, accepted5 October2005.
the northern United States and central Canada, often
building their nests over shallow water on a floating
substrate of matted marsh vegetation. Here, we report
the first nesting record ofthis species on a coastal bar- The North American subspecies of Black
rier island. The nest, which consisted oftwo eggs laid Tern (Chlidonias niger surinamensis) breeds
in a slight scrape ofsand, was located on 6 July 2004 locally across the northern United States and
in a large breeding colony of Common Terns (Sterna central Canada. Black Terns are semicolonial,
hPiarrku.ndNo)ewonBKreulnlsyw’iscIks,laCnadnaatdaK.ouTchheiboobusgeuravcatNiaotnioanlaslo typically nesting in productive, shallow fresh-
water marshes, semipermanent ponds, prairie
represents the current northeastern breeding limit for
this species in North America. Both eggs hatched, but sloughs, and along margins of lakes and rivers
(Stewart and Kantrud 1984, Dunn and Agro
1995, Schummer and Eddleman 2003). Nests
' Dept, ofNatural Resource Sciences, McGill Univ., are generally placed in areas of calm water
Ste-Anne-de-Bellevue, QC H9X 3V9, Canada.
within stands of emergent bulrush Scirpus
2 Dept, ofBiological Sciences, Bishop's Univ., Len- (
noxville, QC JIM 1Z7, Canada. spp.), cattail (Typha spp.), bur-reed (Spargan-
3Corresponding author; e-mail: ium spp.), or pickerelweed (Pontederia corda-
[email protected] ta\ Cuthbert 1954, Dunn 1979, Mazzocchi et
