The Wilson Journal of Ornithology 124(4):767 774, 2012 
FIRST DESCRIPTION OF THE REPRODUCTIVE BIOLOGY OF THE 
GREY-BELLIED HAWK ( ACCIP1TER POLIOGASTER) 
ANDREA LARISSA BOESING, 12 WILLIAN MENQ. 1 AND LUIZ DOS ANJOS' 
ABSTRACT—We observed an active nest of the Grey-bellicd Hawk [Acci/nter poliogaster) in the mixed rainforest of 
southern Brazil during the 2011 breeding season. The nest was a platform built in the branches of the upper part of a Parana 
pine ( Araucaria angustifoha). The clutch size was two eggs, but only a single nestling survived and left the nest. ~49 days 
post-hatching. The fledgling was fed by adults at the nest for at least 90 days post-hatching. Only the adult female incubated 
the e 22 S and brooded the nestlings. Both female and male provided nest defense, the former up to 50 m from the nest and 
the latter at 50 to 200 m. Only the male hunted and only the female fed the nestlings. The identified prey brought to the nest 
by the male included eight birds and one young armadillo. Five voice types were identified: one alarm call, three tood- 
related calls (performed bv adults), and one food-begging call (performed by the fledgling). The type of habitat where the 
nest occurred suggested this poorly known species can possibly survive in disturbed areas. It seems to be naturally rare and 
its' shy behavior contributes to its low detection, Received N February 2012. Accepted 12 July 201.. 
The Grey-bellied llnwk (Accipiier poliogaster) 
is a poorly known species occurring over a large 
area in South America. This species inhabits 
lowland tropical forest, humid secondary growth 
and other dense woodland, and also riverine 
strips, apparently almost entirely below 500 m 
and is perhaps migratory (Ferguson-Lees and 
Christie 2001). It is distributed from northern 
Colombia, the extreme west and south ol 
Venezuela and lowland Guyana and Surinam 
southwards through east Ecuador, northeastern 
Pern and the Amazon, and east Brazil, from south 
to north and east of Bolivia, east Paraguay, and 
the extreme northeast of Argentina (Ferguson- 
Lees and Christie 2001). It is a rare species and is 
poorly known throughout its range (Thiollay 
1994). and is also poorly represented in museum 
collections (Lanzer et al. 2009). It is treated as 
Near-Threatened by Collar et al. (1994). hut the 
species was recently categorized as a species of 
Least Concern by Birdl.ife International (2012). 
Information on the nest and reproductive 
biology of the Grey-bellied Hawk has not been 
described (Bicrregaard 1994. Miirquez cl al. 
2005). and the vocal repertoire and diet ot this 
species are unknown. There arc several short 
articles discussing the possibility of a Grey- 
bellied Hawk nest in Ecuador. This nest was 
described by Vries and Melo (2001) as belonging 
to a Slaty-backed Forest Falcon t Micrastur 
mirandollei), a species with a similar adult 
Departamento dc Biologia Animal c Vegetal. Umversi- 
dade Estadual de I-ondrinS. Rodovia Celso Garcia Cid. 
Campus Universitdrio-Caixa Postal 6001, CEP 86051-980. 
Londrina, Parana. Brasil. 
'Corresponding author; e-mail: lari.boesing@gmail.com 
plumage as the Grey-bellicd Hawk. Thorstrom 
(2002) questioned this designation, because some 
of the nesting habits reported by the authors differ 
markedly from those of the genus Micrastur . 
suggesting the nest described was misidentified as 
belonging to a forest falcon, and instead possibly 
belonged to either a Bicolored Hawk (Accipiter 
bicolor) or Grey-bellied Hawk. 
We made observations on the reproductive 
biology and behavior of the Grey-bellied Hawk 
based on an active nest found in mixed rainforest 
in southern Brazil. We provide the first descrip¬ 
tions of the nest, egg. nestling, and fledgling, as 
well as information on the diet and vocal 
repertoire of this poorly known species. 
METHODS 
Study Site .—The nest was in a disturbed area 
within mixed rainforest in Santa Catarina State, 
southern Brazil at 800 m elevation. This forest 
area. —500 ha in size, has a heavily degraded 
understory because it is used for livestock. In 
particular, the area around the nest (— 200 m 
radius) had a poor understory. Parana pine 
(Araucaria angiislifolia) represented —50-60% 
of the tree species in (his disturbed forest; the 
density of this conifer in mixed rainforest is -40% 
of the individual trees (Oliveira and Rotta 1982) 
and it is the dominant tree species of this forest type 
(Maak 1981. Oliveira and Rotta 1982). Other tree 
species in the study area included Ocotea porosa. 
Ilex paraguariensis, Cedrela fissilis, Lithraea 
molleoicles, and Ocotea odorifera. 
Field Observations. —We made observations 
continually (4 days/week) between 16 September 
and 27 November 2011 with occasional observations 
767 
