Status and Reproductive Outcome of the Breeding Population of Striated Caracaras (Phalcoboenus australis) at Franklin Bay, Staten Island, Argentina

BALZA ULISES; LOIS NICOLAS; RAYA REY A

WILSON JOURNAL OF ORNITHOLOGY

WILSON ORNITHOLOGICAL SOC

Año: 2017 vol. 129 p. 890 - 898

1559-4491

ABSTRACT.?The Striated Caracara (Phalcoboenusaustralis) is a poorly known raptor associated with seabirdcolonies, restricted to the islands of southern South America,and with an estimated extant population of ,2,500 matureindividuals. We evaluated the number of breeding pairs,described the characteristics and spatial pattern of nest sites,and estimated breeding output of a population of StriatedCaracaras in Franklin Bay, Staten Island, Argentina. Wefound one of the lower breeding density values reported forthis species, although this population is associated with oneof the biggest colonies of Rockhopper Penguins. The mainmaterial used for the construction of Striated Caracaras?nests was tussac grass, though only half of nests were placedin grassland. The spatial pattern for nest sites correspondswith global and local clustering. All successful StriatedCaracaras? nests were at least 250 m from the nearestneighboring nest, were generally closer to the colony ofRockhopper Penguins than failed nests, and had moreRockhopper patches around them. Breeding success was0.73 successful nests/active nests, productivity was 1.27 61.01 young/active nest, and brood size was 1.75 6 0.71young/successful nest. The presence of invasive wild goatsand red deer is proposed as a factor that could be restricting nest site availability in the study area.