Striated caracara in Franklin Bay Staten Island, use of resources on an invaded scenario.

LOIS NICOLAS; A RAYA REY; BALZA ULISES; SALOM A

Congreso; Ornithological Congress of the Americas. XVII RAO / XXIV CBO / XCV AFO; 2017

The striated caracara Phalcoboenus australis is a raptor restricted to islands in Southern Argentina and Chile, which during the breeding season (from October to March) is associated with seabird colonies, where it feeds and reproduces. We studied the breeding density, spatial pattern of nest sites and their characteristics of P. australisbreeding population on Franklin Bay (Staten Island, Argentina) during 2014-2015 and 2016-2017 breeding seasons. We found one of the lowest breeding density values report for this species (5.4 nests/Km2, n=20), although this population is associated with one of the biggest colonies of the world of Rockhopper PenguinEudyptes chrysocome. The main material used for the construction of Striated Caracara nests was tussac grass, though only half of the nests were placed in grassland. The spatial pattern for nest sites corresponds with global and local clustering. All successful Striated Caracara nests were at least 250 m away from the nearest neighboring nest and were closer to the Rockhopper Penguin colony than failed nests. Breeding success was 0.73-0.83 successful nests/active nests and productivity was 1.27-1.42 young/active nest. The presence of invasive wild goats (Capra hircus) and red deer (Cervus elaphus), introduced in 1856 and 1974 respectively, is proposed as a factor that could be restricting P. australis nest site availability and modulating part of their population dynamics in the study area.