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

• Main Authors: Balza, U., Lois, N.A., Raya Rey, A.
• Format: Journal/Newspaper
• Language: unknown
• Subjects: Breeding output; Invasive species; Nest site availability; Spatial analysis; breeding population; brood size; colony; habitat availability; nest site; nest structure; raptor; reproductive biology; reproductive success; seabird; Argentina; Canada; Franklin Bay; Northwest Territories; South America; Capra aegagrus; Caracara; Cervus elaphus; Falconidae; Phalcoboenus australis; Raptores; Spheniscidae
• Online Access: https://hdl.handle.net/20.500.12110/paper_15594491_v129_n4_p890_Balza

The Striated Caracara (Phalcoboenus australis) is a poorly known raptor associated with seabird colonies, restricted to the islands of southern South America, and with an estimated extant population of <2,500 mature individuals. We evaluated the number of breeding pairs, described the characteristics and spatial pattern of nest sites, and estimated breeding output of a population of Striated Caracaras in Franklin Bay, Staten Island, Argentina. We found one of the lower breeding density values reported for this species, although this population is associated with one of the biggest colonies of Rockhopper Penguins. The main material used for the construction of Striated Caracaras' nests was tussac grass, though only half of nests were placed in grassland. The spatial pattern for nest sites corresponds with global and local clustering. All successful Striated Caracaras' nests were at least 250 m from the nearest neighboring nest, were generally closer to the colony of Rockhopper Penguins than failed nests, and had more Rockhopper patches around them. Breeding success was 0.73 successful nests/active nests, productivity was 1.27 ± 1.01 young/active nest, and brood size was 1.75 ± 0.71 young/successful nest. The presence of invasive wild goats and red deer is proposed as a factor that could be restricting nest site availability in the study area. © 2017 Wilson Ornithological Society. All rights reserved.