SHORT COMMUNICATIONS 
403 
The Wilson Journal of Ornithology 124( 2):403—405. 2012 
Agonistic Interactions Between Two Foraging Anhinga Females in 
Southeastern Brazil 
Ivan Sazima 1 - 3 and Giulia B. D'Angelo 2 
ABSTRACT—Darters (Anhingidae) are among die 
most territorial Pelecanit'ormes. but most of the observed 
aggression is between nudes and limited primarily to the 
breeding season. We observed three instances of 
agonistic interactions between two female Anhingas 
(Anhinga anhinga) foraging in a pond of an urban park in 
southeastern Brazil. A foraging resident female chased 
another female as soon as it caught sight of the latter 
approaching, which caused the intruder to dive and 
retreat. The resident female vocalized toward the site 
where the intruder disappeared while still in the water. 
The resident then vocalized front a perch from tintc to 
time toward the pond while drying its feathers. We 
played back its recorded call and the bird vocalized 
toward us suggesting this vocalization was territorial. 
Agonistic behavior at foraging sites merits further 
observation to leam whether it is restricted to particular 
individuals and/or periods. Received 21 October 2011. 
Accepted 21 January 2012. 
Darters (Anhingidae) are territorial species of 
Pelecanit'ormes, although they may associate with 
other aquatic birds (Orta 1992, Frederick and 
Siegel-Causey 2000). The Anhinga (Anhinga 
anhinga) forages mostly solitarily in South Amer¬ 
ica (Haverschmidt 1971, Sick 1997). Agonistic 
interactions among Anhingas have been recorded 
at perches and breeding sites with males being 
more aggressive than females (Orta 1992. Freder¬ 
ick and Siegel-Causey 2000). Aggressive interac- 
lions between females at sites other than breeding 
areas and perches arc unrecorded to date to our 
knowledge. We report on agonistic interactions 
between two Anhinga females foraging in a pond 
of an urban park in southeastern Brazil. 
OBSERVATIONS 
We observed Anhinga behaviors at the urban 
park Parque Ecoldgico 'Prof. Hermogenes de 
Freitas Leitao Filho', Campinas (—22 54’ S, 47 
Museu de Zoologia. l/'niversidadc Estadual dc Campi¬ 
nas. 13083-970 Campinas. Sao Paulo. Brazil. 
' Programa de Pbs-Graduayao cm Biologia Animal. Uni- 
versidade Estadual de Campinas, 13083-970 Campinas. Sao 
Paulo, Brazil. 
’Corresponding author: e-mail: isazima@gmail.com 
04' W), Sao Paulo, southeastern Brazil. Females 
arc easily distinguishable from males as the latter 
are black with silvery to white streaks and spots 
on upper back, scapulars, and wing-coverts, 
whereas the former are duller with head, neck, 
and breast huffy (Frederick and Siegel-Causey 
2000). We watched Anhingas in the morning or 
afternoon with the naked eye and through a 70- 
300 telephoto zoom lens mounted on a SLR 
camera from a distance of 3-15 m from 7 January 
to 31 March 2011. We used ad libitum and 
behaviour sampling rules (Martin and Bateson 
1986), both of which are adequate for rare 
behaviors and/or opportunistic records, throughout 
the observations. Vouchers of digital photographs 
are on file at the Museu de Zoologia da 
Universidade Estadual de Campinas (ZUEC). 
Vocalizations were recorded with a Marantz 
PM 13-671 digital recorder and a Scnnheiser ME- 
67 microphone at 24 bit and 48 kHz resolution. The 
recorded vocalizations are at the Fonoteca Neo¬ 
tropical 'Jacques Viclliard', Universidade Estadual 
de Campinas, Brazil. 
We observed a female Anhinga interacting with 
another female on three occasions (16. 22, and 29 
Jan 2011). One of the females was mated to a 
male that occasionally foraged at the same site, as 
both attended the same nest. We observed this 
female ('resident' hereafter) several times in the 
previous year and no aggressive behavior toward 
any bird in the pond was recorded at the time. 
This female was selectively foraging for small 
fish in January at a particular site (22 48' 37" S, 
47 04' 30” W; Fig. 1) near a small bridge from 
which people threw pieces of bread for domestic 
waterfowl and fish (Sazima 2007). This resident 
mostly foraged at the water surface near the 
floating bread (which attracted small fish that 
stayed close to the surface), and it scanned the 
neighborhood visually. As soon as the foraging 
bird observed another female (‘intruder’ hereaf¬ 
ter) approaching from ~50 m distant, the resi¬ 
dent quickly swam towards it (Fig. 2A) gaping 
occasionally. If the intruder did not retreat, the 
