The Gray-bellied Hawk (Accipiter poliogaster) is one of the largest members of the genus Accipiter and occurs in a large range in South America. It occurs mostly in continuous forests and to a lesser extent in semi-disturbed habitats. Apparently, there are two disjunct populations, in Amazonia and in southern Brazil (Figure 2). Despite its size and widespread geographic distribution, little is known about basic aspects of the Gray-bellied Hawk’s natural history and reproductive biology.
Figure 1. Juvenile Gray-bellied Hawk standing on the nest.
An interesting fact about the Gray-bellied Hawk is that juvenile birds have a plumage remarkably similar to that of an adult Ornate Hawk-Eagle (Spizaetus ornatus). Juvenile Gray-bellied hawks were considered a separate species before the realization that they were only a juvenile plumage.
Another interesting fact is that this hawk’s status in Amazonia is poorly understood. Hilty and Brown (1986) suggested that that the Gray-bellied Hawk may be a non-breeding Austral visitor to Amazonia based on the lack of breeding records in Colombia and throughout most of its range.
Ridgely and Greenfield (2001) reported sightings in Ecuador during the Austral summer, suggesting that the bird occurs throughout its range all year round in very low numbers.
Figure 2. Approximate geographic distribution of the Gray-bellied Hawk in Amazonia and Southern Brazil (blue areas). Red dot= Location of Los Amigos Biological Station. Yellow dots= Approximate location of nests in Southern Brazil.
More recently, Boesing et al (2012) found the first nest of a Gray-bellied Hawk and studied its nesting biology in the State of Santa Catarina in Southern Brazil. Since then, additional nests have been found in the region of Southern Brazil.
Table 1. Breeding records of Gray-bellied Hawk in Southern Brazil. These records are based on photographic evidence obtained from www.wikiaves.org.
|Two chicks standing on the
nest, growing feathers through
|Irineópolis/Santa Catarina 02/11/2011||Larissa Boesing|
|Nest with an adult sitting on it.||Nova Trento/Santa Catarina 15/09/2012||Evair Legal|
|Adult sitting on nest||Ribeirão Grande/Sao Paulo 04/11/2016||André Mendonça|
|Adult and one chick in downy feathers.||Iporanga/Sao Paulo
|Nest with apparently adult sitting
|Ribeirão Grande/Sao Paulo
First Breeding Record of Gray-bellied Hawk In Amazonia
On April 15, 2018, along one of the trails at Los Amigos Biological Station in southeastern Peru, birding guide Cesar Bollatty observed a medium-sized raptor on an exposed branch some 35 meters (m) above the ground. At first, the bird looked like an Ornate Hawk-Eagle but its small size and appearance suggested that it was a juvenile of the rare Gray-bellied Hawk. The bird was observed by Cesar Bollatty and birding companion Alfonso Escajadillo for approximately 35 minutes before it flew into the forest out of sight.
Figure 3. Bird photographed at about 6 m above the ground.
The next morning Cesar and Alfonso returned to the area with the purpose of taking better photos of the bird. After some search, a juvenile Gray-bellied Hawk was located perched on a branch overhanging the edges of a small pond at approximately 6 m above the water. The bird appeared to be hunting as it was persistently looking down at the water. After a few minutes, the bird flew up to the dense canopy of the forest where it was lost temporarily.
As the observers scanned the forest canopy for the bird at the area it flew into, their attention turned to a flying juvenile Gray-bellied Hawk that landed on a large nest where it was observed and photographed multiple times. After approximately 15 minutes, another juvenile Gray-bellied Hawk appeared from the forest and joined the first bird on the nest. Both birds were observed eating a prey item on the nest. After some time on the nest, one bird flew back to the nearby pond. The two observers followed the bird and located it again at the edge of the pond where many additional photos were taken. The arrival of the second bird and the two birds on the nest were recorded on video.
Figure 4. Juvenile Gray-bellied Hawk.
Before the discovery of this nest, a pair of adult Gray-bellied Hawks was reported multiple times in the general area along the trails of the “Los Amigos” Biological Station.
Using 33 days (1) as incubation period, 49 days as the time between hatching and fledging (2) and 90 days (3) as the time Gray-bellied Hawk chicks remain in the surroundings of the nest, it was estimated that this pair laid eggs approximately in mid-November, 2017. This estimation is consistent with the September through December nesting period of the Gray-bellied Hawk in Southern Brazil.
This nest constitutes the first breeding record of the Gray-bellied Hawk within the range of the Amazonian population.
The estimated mid-November, as the approximate date this pair of hawks laid eggs, marks a point within the breeding season of the Gray-bellied Hawk in Amazonia. The month of November also falls within the nesting season of this hawk in the population in Southern Brazil, based on the breeding records presented in Table 1.
Nesting records of the Gray-bellied Hawk in Amazonia an in Southern Brazil suggest that both populations breed during the same months of the year. Hence, suggesting that the Gray-bellied Hawk is indeed a rare breeding resident in Amazonia and not an Austral migrant to the region.
(1) 33 days is the approximate incubation period of the Accipiter bicolor, a large Neotropical Accipiter (www.globalraptors.org/).
(2) 49 days is the time period between hatching and fledging observed by Boesing et al (2012).
(3) 90 days is the time juvenile Gray-bellied Hawks remained around the nest after fledging (Boesing et al 2012).
- Boesing, Larissa, Willian Menq , and Luiz Dos Anjos. First Description of the Reproductive Biology of the Grey-bellied Hawk (Accipiter poliogaster). The Wilson Journal of Ornithology, 124(4):767-774. 2012.
- Hilty Steven, and W. L. Brown. 1986. Guide to the Birds of Colombia. Princeton University Press.
- Ridgely Robert and Paul Greenfield. 2001. The Birds of Ecuador. Cornell University Press.