Abundance of Harpy and Crested Eagles from a reservoir-impact area in the Low- and Mid-Xingu River

Abstract

In the Brazilian Amazon, two monospecific genera, the Harpy Eagle and Crested Eagle have low densities and are classified by IUCN as Near Threatened due to habitat loss, deforestation, habitat degradation and hunting. In this study, we evaluate occurrence of these large raptors using the environmental surveys database from Belo Monte Hydroelectric Power Plant. Integrating the dataset from two methods, we plotted a distribution map along the Xingu River, including records over a 276-km stretch of river. Terrestrial surveys (RAPELD method) were more efficient for detecting large raptors than standardized aquatic surveys, although the latter were complementary in areas without modules. About 53% of the records were obtained during activities of wildlife rescue/flushing, vegetation suppression or in transit. Between 2012 and 2014, four Harpy Eagles were removed from the wild; two shooting victims, one injured by collision with power lines and one hit by a vehicle. Also, seven nests were mapped. The mean distance between Harpy Eagle records was 15 km along the river channel, with a mean of 20 km between nests near the channel, which allowed us to estimate 20 possible pairs using the alluvial forest, riverine forest and forest fragments. Territories of another ten pairs will probably be affected by inundation of the Volta Grande channel, which is far from the main river. The average distance between Crested Eagle records was 16 km along the river channel. The only nest found was 1.3 km away from a Harpy Eagle nest. The remnant forests are under threat of being replaced by cattle pastures, so we recommend that permanently protected riparian vegetation borders (APP) be guaranteed, and that forest fragments within 5 km of the river be conserved to maintain eagle populations.Keywords: neotropical raptors, Amazon, hydroelectric power plant, environmental impact, Accipitridae. Abundância de Gavião-real e Gavião-real falso numa área sob impacto de reservatório no Baixo e Médio rio XinguResumo Na Amazônia brasileira dois gêneros mono-específicos, Harpia e Morphnus, caracterizam-se por baixa densidade e estão classificados pelo IUCN como Quase Ameaçados, porém ocorrem sobre grande parte do território nacional, suas principais ameaças são a fragmentação florestal, a degradação de hábitat e a caça. Neste estudo avaliamos a abundância destas duas grandes aves de rapina utilizando a base de dados dos programas ambientais da UHE BeloBraz.

Resource availability and diet in Harpy Eagle breeding territories on the Xingu River, Brazilian Amazon

“…A buffer zone radius of ≈ 4.3 km was estimated in this region based on distance among three neighbor nests (Sanaiotti et al, 2015). These areas together will be important for wildlife conservation inside the Belo Monte Hydroelectric Complex, as well as, needs to be included in the Brazilian National Protected Area System (Brasil, 2000), to connect habitats (Brasil, 2012), maintain food resource availability, habitat quality and allow all pairs to successfully reproduce.…”

Ex situ population of the Harpy Eagle and its potential for integrated conservation

“…The Harpy Eagle ( Harpia harpyja Linnaeus, 1758) is a bird of prey and a top predator with a large carrying capacity ( Voous 1969 ). With a low population density and slow reproductive rate in nature, the Harpy Eagle relies on conservation action plans and is the subject of extensive research projects ( Soares et al 2008 ; Brasil 2014b ; Aguiar-Silva et al 2015 ; Sanaiotti et al 2015 ; Watson et al 2016 ; Oliveira 2018 ).…”

Habitat resource overlap in two broad-ranged sympatric Neotropical forest eagles

“…Generally, the crested eagle feeds on smaller and more diverse prey than the harpy eagle, mainly arboreal snakes, small primates, opossums, and birds (Bierregaard 1984;Julliot 1994;Robinson 1994; Whitacre et al 2012;Gomes et al 2021), whereas harpy eagle diet is largely comprised of large arboreal mammals, primarily sloths and primates (Aguiar-Silva et al 2014;Miranda 2015). Thus, crested and harpy eagles may be able to co-exist by partitioning food resources, avoiding direct competition (Sanaiotti et al 2015). On a microhabitat scale, the two species may use differing forest canopy strata for breeding and hunting (Gomes et al 2021), with harpy eagles nesting in canopy-emergent trees (Sanaiotti et al 2015;Miranda et al 2020) and crested eagles canopy trees (Bierregaard 1984;Whitacre et al 2012).…”

“…Thus, crested and harpy eagles may be able to co-exist by partitioning food resources, avoiding direct competition (Sanaiotti et al 2015). On a microhabitat scale, the two species may use differing forest canopy strata for breeding and hunting (Gomes et al 2021), with harpy eagles nesting in canopy-emergent trees (Sanaiotti et al 2015;Miranda et al 2020) and crested eagles canopy trees (Bierregaard 1984;Whitacre et al 2012).…”

“…Apart from localized observations reporting both Harpiinae eagles breeding within ~1 to 3 km of each other in similar habitats (Galetti et al 1997;Muñiz-López et al 2007;Sanaiotti et al 2015), little is known about how these two eagles co-exist at a large biogeographical scale with highly overlapping geographic ranges. Both eagles were recorded in similar forest habitats from two landscape habitat selection studies, one in an 800-ha section of Amazonian Peru (Manu National Park; Robinson 1994), and the second along a 276 km stretch of the Xingu river in Amazonian Brazil (Sanaiotti et al 2015). Harpy eagles were observed more frequently than crested eagles, suggesting the harpy eagle may be the more common of the two species where both are present.…”