Presentación Invitada: Ecology of near-threatened Sickle-winged Nightjar in grasslands of northern Argentina

KRISTINA COCKLE; OLGA VILLALBA; NESTOR FARIÑA; ALEJANDRO PIETREK; ALEJANDRO BODRATI; LUIS PAGANO

Conferencia; AOS & SCO-SOC 2021 Virtual Meeting; 2021

Aerial insectivores are likely declining in the Neotropics, but their conservation is complicated by large knowledge gaps regarding their life history and habitat requirements. Using spotlighting, banding and radio-tracking (2012–2021), we examined habitat use, home-range size and age- and sex-specific survivorship of near-threatened Sickle-winged Nightjars (Eleothreptus anomalus) in a grassland reserve in northeastern Argentina. Sickle-winged Nightjars (216 banded, 8 radio-tagged) exclusively used native tall grassland for foraging, roosting, and nesting, avoiding exotic pine plantations, but using areas recently cleared of pines in restoration efforts. 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 (50% kernel adult male: 17 ± 7 ha; adult female: 84 ± 44; 1-yr old male: 162 ± 59 [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. A yearling male was captured 4.3 km from where it hatched. Yearlings developed a brood patch (female) and performed displays (male). According to our best-supported Cormack-Jolly-Seber model, detectability was four times higher for males than females, and annual survival 40% higher for adults than juveniles. 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, as well as conservation actions to protect South American grasslands from exotic pine plantations and agro-industry.