SHORT COMMUNICATIONS 
607 
development to androgen levels develop more 
aggressive behaviors towards conspecific chicks 
and adults. This has been demonstrated in the 
N'azcaBooby (Sula granti) (Anderson et al. 2004. 
Muller et al. 2008) and the Black-headed Gull 
I Chroicocephalus ridibundus ) (Ros el al. 2002), 
both colonially-nesting seabird species. 
There are many reports in the literature ol 
egression and cannibalism by adults consuming 
eggs, chicks or body parts of other individuals 
fStanback and Koenig 1992). but little is known 
about the occurrence of these behaviors by 
fledglings and young birds. To our knowledge, 
our observations constitute the first report of 
aggression and cannibalism in Peruvian Pelican 
fledglings. 
ACKNOWLEDGMENTS 
We thunk D. W. Mock and M. T. Stanback for help with 
literature. Funding was provided by research grant DI-4S- 
10 from the Vicerrectoria de Investigacion y Doetorado. 
Universidud Andres Bello (Chile), The Milwaukee County 
Zoo. and the Zoological Society of Milwaukee (USA). We 
are also grateful toConsejo de Monumentos Naeionalcs and 
Cofradia Nautica del Paeifico (especially to F Carlicr) for 
granting access to the island. R. S, Wallace kindly corrected 
early versions of the manuscript. We thank Christina Riehl 
and an anonymous reviewer for their comments on the 
manuscript. 
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