Extreme genetic similarity does not predict non‐breeding distribution of two closely related warblers

Abstract

Detailed knowledge of migratory connectivity can facilitate effective conservation of Neotropical migrants by helping biologists understand where and when populations may be most limited. We studied the migratory behavior and non‐breeding distribution of two closely related species of conservation concern, the Golden‐winged Warbler (Vermivora chrysoptera) and Blue‐winged Warbler (Vermivora cyanoptera). Although both species have undergone dynamic range shifts and population changes attributed to habitat loss and social interactions promoting competition and hybridization, full life‐cycle conservation planning has been limited by a lack of information about their non‐breeding ecology. Because recent work has demonstrated that the two species are nearly identical genetically, we predicted that individuals from a single breeding population would have similar migratory timing and overwintering locations. In 2015, we placed light‐level geolocators on 25 males of both species and hybrids in an area of breeding sympatry at the Fort Drum Military Installation in Jefferson and Lewis counties, New York. Despite extreme genetic similarity, non‐breeding locations and duration of migration differed among genotypes. Golden‐winged Warblers (N = 2) overwintered > 1900 km southeast of the nearest Blue‐winged Warbler (N = 3) and spent nearly twice as many days in migration; hybrids (N = 2) had intermediate wintering distributions and migratory timing. Spring migration departure dates were staggered based on distance from the breeding area, and all birds arrived at the breeding site within 8 days of each other. Our results show that Golden‐winged Warblers and Blue‐winged Warblers in our study area retain species‐specific non‐breeding locations despite extreme genetic similarity, and suggest that non‐breeding locations and migratory timing vary along a genetic gradient. If the migratory period is limiting for these species, our results also suggest that Golden‐winged Warblers in our study population may be more vulnerable to population decline than Blue‐winged Warblers because they spend almost twice as many days migrating.

Geolocators reveal migratory connectivity between wintering and breeding areas of Golden-winged Warblers

“…, Bennett et al. , Kramer et al. ), regional differences in winter habitat conditions may be contributing to differences in population trends in different breeding areas.…”

“…, Bennett et al. ). As a behavioral model, we set a gamma flight speed distribution (shape = 0.7, scale = 0.08, maximum flight speed = 60 km/h; Pennycuick et al.…”

“…The results of geolocator‐based studies published to date suggest that Golden‐winged Warblers exhibit a strong pattern of migratory connectivity (Bennett et al. , Kramer et al. ).…”

“…Research and conservation efforts in the wintering areas of Golden-winged Warblers have also increased in recent years . These efforts include studies focused on better understanding their distribution, resource selection, and space use in portions of their wintering range (Chandler and King 2011, Bennett 2012, Chandler et al 2013, 2016. The results of these studies are being used to guide conservation actions that target Golden-winged Warblers, including the development and implementation of sustainable agricultural practices that provide quality wintering habitat (Chandler et al 2013.…”

“…The results of geolocator-based studies published to date suggest that Golden-winged Warblers exhibit a strong pattern of migratory connectivity (Bennett et al 2017, Kramer et al 2017). However, continued efforts to further elucidate aspects of migratory connectivity for wintering and breeding populations of Golden-winged Warblers would help facilitate effective conservation and management actions by allowing conservationists to ensure that conservation efforts in breeding and nonbreeding areas coincide with observed patterns of migratory connectivity.…”