SHORT COMMUNICATIONS 
603 
The Wilson Journal of Ornithology 124(3):603-607, 2012 
Fledgling Peruvian Pelicans (.Pelecanus thagus) Attack and Consume Younger 
Unrelated Conspecifics 
Maximiliano Daigre , 1 Paulina Arce,' and Alejandro Simeone 12 
ABSTRACT.—Aggression between chicks and fledg- 
lings. at limes ending in siblicide and cannibalism, has 
been mostly studied among nest mates. It is Frequent 
among colonial-nesting birds and is usually related to 
competition for limiting resources (e.g.. food and space) 
and competitive disparities between siblings, among 
other factors. We report three observations of fully- 
grown Peruvian Pelican l Pelecanus thagus t fledglings 
attacking unrelated eonspecitlc nestlings at a breeding 
colony in central Chile. One case ended in cannibalism. 
Five elements were common in all three cases: (I) 
nestlings that were attacked were left unattended by their 
parents in the nest. (2) nestlings that were attacked were 
newlv hatched (up to 5 days of age). (3) aggressors were 
fully-grown fledglings (60-75 days of age). (4) aggres¬ 
sive fledglings always attacked nestlings in groups, and 
(5) all cases were observed late in the breeding season. 
We suggest aggression toward and cannibalism of 
nestlings by fledglings arc opportunistic behaviors, based 
on the opportunity of finding unattended nests and arc 
triggered by food deprivation, although hormonal 
mechanisms may also be involved. Our observations 
constitute the first report of aggression and cannibalism 
hy Peruvian Pelican fledglings. Received 20 January 
2012. Accepted IS April 2012. 
Aggression in chicks and fledglings has been 
typically studied in the context of sibling rivalry 
'Gill 2007). Aggression may positively relate to 
food limitation; nest mates compete for food and 
aggressive interactions may end in siblicide 
(Mock 1984. Mock and Parker 1997) and even 
cannibalism (Stanback and Koenig 1992). Mock 
cl al. (2009) suggested besides competition for 
food, the way in which food is provisioned to 
chicks, weaponry, competitive disparities between 
siblings, and spatial confinement are also impor¬ 
tant factors driving siblicide. These conflicts are 
most frequent in dense breeding colonies, where 
there is competition lor limited resources such as 
food and nesting space (Mock 1984. Stanback and 
Koenig 1992). 
1 Departamento de Ecologia y Biodiversidad, Facultad de 
Ecolugia y Recursos Naturales. IJniversidad Andres Bello. 
Republica 470. Santiago. Chile. 
Corresponding author; e-mail; asimeone@unab.cl 
Aggressive acts among seabirds and between 
siblings involving siblicide (Drummond 1987; 
Anderson 1990a. b) and cannibalism (Stanback 
and Koenig 1992), have been well documented in 
Pclccaniformes, particularly boobies (Sitla spp.) and 
pelicans (Pelecanus spp.). Sachs and Jodice (2009) 
observed aggression among sibling Brown Pelicans 
(P. occidentalism and Nelson (2005) reported 
siblicide as consequence of fights for food by this 
species. Smith and Munro (2008) observed canni¬ 
balism by Australian Pelicans (P. conspicillatus) of 
small chicks hy young from the same season. We 
report the first observations of aggression and 
cannibalism among unrelated Peruvian Pelican (P. 
tlutgus) chicks at a breeding site in central Chile. 
METHODS 
We conducted observations at Pajaro Nino 
Island (33 21' S; 71 41 1 W ) in Algarrobo, central 
Chile. Pajaro Nino is a 3-ha island that was joined 
to the mainland in 1977 lo build a marina. The site 
regularly supports colonies of Humboldt Penguins 
(Spheniscus luunholdti). Neotropic Cormorants, 
(Phalacrocorax hrasilianus). Kelp Gulls (Lams 
dominicanus), ancl Peruvian Pelicans (Simeone 
and Bernal 2000, Simeone et al. 2003). Peruvian 
Pelicans in the area breed asynchronously, laying 
from mid-December throughout mid-April with the 
last chicks fledging in June. Breeding numbers 
ranged from 4.000 pairs in 2009/2010 to 7,000 
pairs in 2010/2011 (pers. obs.). 
Two observers visited and observed the pelican 
colony every' 15 days from December to June (each 
time from 1200 lo 1600 hrs) during the 2009/2010 
and 2010/2011 breeding seasons using 10 X 42 
binoculars. Canon SX10 IS and Canon SX20 IS 
digital cameras were used to collect photographic 
data. We documented at each aggression event: 
number and age of birds involved, duration of the 
event, and outcome ot the aggression (attacked bird 
injured, survived and left alone, killed, or bird 
predated). The ages of involved chicks followed 
the description of Schreiber (1976) for Brown 
Pelicans and our own observations. 
