Boesing et al • REPRODUCTION OF THE GREY-BELLIED HAWK 
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FIG. I. The nest of the Grey-bellied I lawk in the upper pari of a Parana pine in the mixed rainforest of southern Brazil. 
IA) Inner nest: the newly hatched nestling (on the right) and an egg (on the left) on 26 September 201 I: (B) the nest and 
female Grey-bellied Hawk: (Cl nestlings 6 weeks post-hatching (2 Nov 2011): (D) fledgling 9 weeks post-hatching (23 
Nov 2011). 
distance of 20 m before the female chased it away. 
A juvenile Yellow-headed Cararaca in another 
situation ventured close to the nest and was 
frightened away by skimming of the female. 
Hunting and Food Provisioning. —The male's 
role during both incubation and post-hatching 
periods was mainly providing food for both 
female and nestlings/flcdgling. The male brought 
prey to the female during the incubation period to 
feed upon on the nest. The male continued to 
bring food to the female during the nestling 
period, which she used to feed herself and also 
tore it into pieces before delivering it to die 
nestlings (up to the sixth week: — 42 days). The 
nestlings began to feed themselves at -20 days, 
but female assistance, by tearing the prey into 
pieces, was usually observed. The male letl the 
food in the nest for the chicks to start feeding 
themselves after -42 days. It was at this point 
that the first sign of competition between the 
nestlings appeared, normally occurring when the 
male left the prey in the nest. The faster nestling 
would take the prey using its claws and feed itself, 
not allowing the other chick to feed. The other 
chick would remain attentive and, if its sibling 
was distracted, would steal the prey. 
The prey was delivered by the male to the 
female within a radius of -50 m of the nest 
(during the incubation/nesting periods), or was 
left on the nest (during the fledging period). The 
hunts, undertaken only by the male, more 
frequently occurred in the early morning and 
before sunset (Fig. 2). Twelve of 22 occasions 
when we observed the male bringing food were 
early in the morning (0600-0900 hrs) and seven 
were in the later afternoon (1600-1900 hrs). Prey 
were brought outside of these times (at — 1400 
hrs) on just three occasions. It was possible to 
make a general identification of nine of the prey 
items: eight were small birds, probably Columbi- 
dae, and one was a mammal, probably a young 
armadillo. The female dropped the carcass of a 
