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Prey of breeding Chilean hawks (Accipiter chilensis) in an Andean nothofagus forest in Northern Patagonia.

Article Excerpt
The loss of old-growth, native forests is the most serious threat to the flora and fauna of the Patagonian temperate forest region (Fuentes 1994). The endemic, forest-specialist fauna--including various raptors (Jaksic and Jimenez 1986, Stotz et al. 1996)--is the most critically threatened (Willson et al. 1994, Kelt 2001). However, the secretive behavior and low population densities of forest raptors, and the complexity of their habitats, make them very difficult to study (Thiollay 1996, Bierregaard 1998). With the exception of the Rufous-legged Owl (Strix rujipes; Martinez and Jaksic 1996, 1997; Diaz 1999), Chilean forest raptors are not well-studied. Because raptors are top-level predators and generally have large home ranges, an understanding of their ecological requirements is crucial, particularly for those that are habitat specialists (Bierregaard 1998).

The Chilean Hawk (Accipiter chilensis; Thiollay 1994) is one of the least studied raptors in the Patagonian temperate forest. This hawk has been listed as rare throughout its entire range (Jaksic and Jimenez 1986), although it is considered relatively common in the Cape Horn province (Venegas and Sielfeld 1998). Its populations are considered threatened due to increasing habitat loss from extensive fires, logging pressures, and hunting (Jaksic and Jimenez 1986). Most of what we know of the Chilean Hawk's biology is descriptive (e.g., Housse 1945, Johnson 1965); what is known about its habitat, feeding, breeding, and movements was summarized by Thiollay (1994). Here, we report on the Chilean Hawk's diet during the breeding season in the Andean Nothofagus forest of Nevados de Chillan, northern Patagonia.

METHODS

Our study was conducted in the Huemules del Niblinto Nature Sanctuary and National Reserve (36 [degrees]45' S, 71 [degrees] 29' W; 50 km east of Chillfin), located in northernmost Patagonia (36-56[degrees] S; see Vuilleumier 1985). Niblinto is a private/public wildlife area (~10,000 ha) that forms part of the Nevados de Chillan, a priority site for biodiversity conservation in Chile (Munoz et al. 1996). The landscape around the Nevados de Chillan is rugged, composed of fairly narrow valleys and high hills (800-2,500 m elevation, [greater than or equal to] 45[degrees] slopes). The climate is Mediterranean, characterized by dry, warm (20-30[degrees] C) summers and cold (0 10[degrees] C), wet (rainy and snowy) winters (mean annual precipitation > 1,000 mm).

In February 2000, we began an ecological study of high-Andean and forest raptors of Nevados de Chillan. Our objectives were to (1) determine their diets and relationships to prey abundance, (2) describe their breeding biology, and (3) study their hunting behavior. We studied the diet of breeding Chilean Hawks from prey remains collected during the austral summers of 2001-2002 and 2002-2003 at two nest sites (A and B; 7 km apart) located along the Niblinto river valley. This valley is dominated by shrublands and second-growth, mixed-deciduous forest composed of Nothofagus dombeyi, N....

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