Habitat Selection and Foraging Ecology of Raptors in Amazonian Peru

Abstract

Census results and observations of foraging tactics and diet were compiled for the 35 regularly occurring species of diurnal raptors in an 800-ha section of the lowland Manu National Park of southeastern Peru. Census results show that most forest raptors occurred across a broad array of successional stages. Population densities ranged from a high of one or two territories per 100 ha (e.g., Micrastur forest-falcons, double-toothed kite, Harpagus bidentatus) to lows of much less than one territory in the entire study area (e.g., large eagles). A species replacement apparently occurs in the genus Leucopternis, with the slate-colored hawk L. schistacea occupying flood plain forest and the white-browed hawk L. kubli occupying upland forest. All other congeners showed substantial overlap in habitat use. Based on observations by 35 researchers of over 400 prey items being carried and over 200 attacks, I divided raptors into several preliminary guilds. Forest raptors include seven species that hunt arthropods and small vertebrates from concealed perches (e.g., Micrastur forest-falcons, gray-headed kite, Leptodon cayanensis); seven species that hunt large birds and mammals either from concealed perches (e.g., ornate hawk-eagle, Spizaetus ornatus) or on long-range attacks on sites where birds or mammals aggregate (e.g., bicolored hawk, Accipiter bicolor); and several species with specialized diets of wasps (red-throated caracara, Daptrius americanus), snails (hook-billed kite, Chondrohierax uncinatus), and snakes (laughing falcon, Herpetotheres cachinnans). Species that hunt on the wing include four that feed mostly on flying insects and small vertebrates (two kites, the short-tailed hawk Buteo brachyurus, and the bat falcon Falco rufigularis), one that dives on perched vertebrates (zone-tailed hawk Buteo albonotatus), and two vultures that search for carrion. Raptors of open rivers, lakes, and marshes indude a fish specialist (the osprey Pandion haliaetus), two snail specialist kites, a carrion-eating vulture, a Buteo that dives on arthropods and small vertebrates, and three species with extremely diverse diets (e.g., black-collared hawk, Busarellus nigricollis). Snail specialists tended to occur irregularly during the eleven field seasons of this study. Several raptors are known to influence the population dynamics of their prey species. Large forest-dwelling raptors such as the harpy and crested eagles are likely to require the largest preserves.