SHORT COMMUNICATIONS 
405 
FIG. 3. (A) The resident female vocalizing in the 
direction of the site where the intruder disappeared, while 
swimming toward the bank. (B) The resident female 
vocalizing in the direction of the pond. 
leaves no doubt the calls were uttered within a 
territorial context. Thus, defense of an unusually 
rewarding foraging site is the most parsimonious 
explanation we have for the agonistic encounters 
between the two females. 
Agonistic interactions between Anhinga fe¬ 
males seem uncommon at foraging areas, and 
this behavior merits further observation to ascer¬ 
tain if it is restricted to particular individuals and/ 
or periods, or if these interactions have gone 
unnoticed due to the secretive habits of these 
FIG. 4. Sound spectrogram of a territorial call (# 
11888. Fonoteca Neotropical ‘Jacques Vielliard', Universi- 
dade Estadual de Campinas) uttered by the resident female 
while perched on a dead branch near the bank. 
birds (Haverschmidt 1971. Orta 1992, Sick 1997, 
Frederick and Siegel-Causey 2000). 
ACKNOWLEDGMENTS 
We are most grateful to Milena Corbo and Arthur 
Macarrao for recording the vocalizations with us (MC also 
for the resulting sound spectrograms and help with their 
description), Celso L. D'Angelo for expert advice about the 
aerial image of the park. Micael Nagai for company in the 
field. CNPq for earlier financial support to JS and CAPES 
for a grant to GBD. and the editor and two anonymous 
referees for considerably improving our paper. 
LITERATURE CITED 
Frederick, P. C. and D. Siegel-Causey. 2000. Anhinga 
(Anhinga anhinga). The birds of North America. 
Number 522. 
Haverschmidt. E 1971 Birds of Surinam. Oliver and 
Boyd, Edinburgh,. United Kingdom 
Martin. P. AND P, Bateson. 1986. Measuring behaviour, 
an introductory guide. Cambridge University Press. 
Cambridge, United Kingdom. 
Orta, .1. 1992. Family Anhingidae (darters). Pages 354-361 
in Handbook of the birds of tlte world. Volume 1. 
Ostrich to ducks (J. del Hoyo, A. Elliott, and J. 
Sargatal. Editors). Lynx Editions. Barcelona, Spain. 
Sa/.ima, 1. 2007. Frustrated fisher: geese and tilapia spoil 
bait-fishing by the Green Heron (Butorides striata) in 
an urban park in southeastern Brazil. Revista Brasi- 
leira de Ornitologia 15:611-614. 
Sick, H. 1997. Ornitologia brasileira. F.ditora Nova 
Fronteira, Rio dc Janeiro. Brazil. 
