Póster: Tracking a declining aerial insectivore, Common Nighthawk (Chordeiles minor), from a wintering site in Argentina (Poster)

KRISTINA L COCKLE; LUIS G PAGANO; OLGA VILLALBA; ALEJANDRO BODRATI; NESTOR FARIÑA

Congreso; VII North American Ornithological Conference; 2020

American Ornithological Society & otros

Migratory aerial insectivores are declining across North America, but hypothesized drivers ? habitat loss, prey declines, toxins ? may well act in South America. In northeastern Argentina, we studied the ecology of Common Nighthawk (Chordeiles minor; CONI), a declining long-distance migrant, and near-threatened Sickle-winged Nightjar (Eleothreptus anomalus; SWNJ), a South American grassland endemic, using spotlighting, banding, GPS-loggers and radio-tags (2012?2020). CONI arrived November-January, finished moulting primaries, and gained body mass (12%) before departing in March. Two females spent May-August in Florida (Citrus WMA and Naples), then 1?3 months in Cerrado (Brasnorte and Ilha do Bananal) surrounded by soybean agroindustry, near wintering sites of CONI that bred in boreal forest, suggesting the Cerrado-Amazon ecotone may be critical even for migrants that "winter" farther south. SWNJ (141 banded, 8 radio-tagged) exclusively used native tall grassland, avoiding pine plantations. Males were smaller than females, detected four times more often, displayed at specific points along roads, never had brood patches, and foraged over smaller, overlapping home ranges (male: 110 ± 57 ha; female: 367 ± 162 [mean ± SE, n = 6]) encompassing display sites, suggesting a lek-like mating system that may require hundreds of hectares of contiguous native grassland to maintain populations. Since 1996 the study region saw a doubling in plantation cover and 900% increase in insecticide use, highlighting the urgency for studies of aerial insectivore diets, prey availability, and toxicity. A top priority for migrant and resident aerial insectivores is to protect native Cerrado and southern South American grasslands from agro-industry.