Appalachian-breeding Vermivora chrysoptera (Golden-winged Warbler) occur at very low densities in mid-elevation forests and agroforestry systems throughout the Andes and isolated massifs of northern Colombia

Vermivora chrysoptera (Golden-winged Warbler) is one of the most striking but also one of the most vulnerable migratory warblers on Earth. To understand its nonbreeding ecology in northern South America, where the steeply declining Appalachian-breeding population is known to spend the nonbreeding season, we conducted 2,534 surveys between 2018 and 2023 in isolated massifs and the Andes of Colombia. Our goal was to evaluate the distribution, detection rates, elevational range, habitat preferences, and microhabitat associations of the species. We obtained 54 detections, with a very low detection rate (2.13%) compared to rates reported from Central America (~10%). Detections covered a wide range of elevations (634–2,551 m above sea level [m.a.s.l.]), with support for a mid-elevation peak at around 1,750 m.a.s.l. Importantly, detection elevation was negatively correlated with latitude such that peak abundances occurred at higher elevations closer to the equator. Most detections were in mature or secondary forests (72%), but birds also occurred along forest edges (17%) and in agroforestry systems (11%), such as shade-grown coffee. We found weak evidence for a female preference for lower elevations as well as more frequent use of agroforestry systems relative to males. Logistic regressions provided some support for a preference for forest over agriculture in both sexes as well as a higher detection probability at points with intermediate canopy height and canopy cover. Our results highlight the low density at which the species occurs across the northern Andes of Colombia and other isolated massifs. The association with forested habitats and the relatively narrow elevation range occupied by most birds implies that focusing conservation efforts on protecting or restoring forests at elevations where detection rates peaked would likely be an effective strategy for ensuring that nonbreeding habitat remains for Appalachian-breeding V. chrysoptera.