BREEDING ECOLOGY, NESTING HABITAT AND THREATS TO A BLACK-AND-CHESTNUT EAGLE SPIZAETUS ISIDORI POPULATION IN THE MONTANE FORESTS OF CENTRAL PERU

Abstract

The Black-and-chestnut Eagle Spizaetus isidori is an endangered and little-known top predator of South American montane forests. To better understand the breeding ecology and threats of this eagle, we studied several pairs between 2017 and 2022 in the central Andes of Peru. We recorded 62 adults, one immature, and 36 juveniles in 36 territories. These territories were in mountainous areas (altitudinal range 690–3,810 m a.s.l.), widely covered by montane forests (43.8–99.7% cover), and secondarily by open land (0.3–56.2% cover), far from urban settlements (1.3–27.1 km). Nesting sites (N = 15) were at medium altitudes (1,330–2,330 m a.s.l.) in steep hillsides or ravines (15–55°), having no preferential cardinal orientation, and relatively close to permanent water courses (20–800 m), open areas (30–930 m) and sites with human activity (120–2,200 m). Nests (N = 15) were placed at the top of tall (28–40 m) and thick-stemmed (DBH range 0.53–1.52 m) emergent trees of nine genera, with Ficus and Juglans being the most used. Incubation and brood-rearing occurred during the dry season (Mar–Nov). The wooded slopes where the eagles nested are being replaced by crops and livestock pastures, causing an estimated loss of 218.2 km2 of forest cover in our study area (5,056 km2) during the last 20 years. We detected human persecution in 55.5% of the territories, resulting in 26 juveniles, four adults, two immatures, and nine unaged eagles killed. Preventing the local extinctions of these eagles will require long-term population monitoring, improving knowledge of its ecology, mitigation of human-eagle conflict, development of education programs, and strengthening of land use inspection.