Nonbreeding ecology and conservation of migratory landbirds with a focus on the Golden-winged Warbler (Vermivora chrysoptera)

Abstract

Conservation of long-distance migratory birds is complicated by an annual cycle that spans broad geographies. Although these populations are affected by events throughout the year, basic knowledge of nonbreeding habitat selection, habitat quality, and migratory connectivity is often lacking. Habitat conservation is further challenged by behaviors, such as intraspecific competition and niche specialization, that can lead males and females to occupy different nonbreeding regions and habitats. This dissertation aimed to fill knowledge gaps regarding habitat selection, quality, and connectivity, with a special focus on cases where males and females segregate spatially. Specifically, we examined (1) the prevalence of sexual segregation among migratory landbirds and the degree to which conservation plans considered the behavior; (2) patterns, drivers, and conservation implications of sexual segregation in declining population of the Golden-winged Warbler (Vermivora chrysoptera); and (3) migratory connectivity and migration strategies for the Golden-winged Warbler and the closely related Blue-winged Warbler (Vermivora cyanoptera). Our review of the published literature and conservation plans for 66 North American migratory landbirds of concern revealed that sexual segregation is a relatively common phenomenon yet is systematically overlooked in conservation plans. Working across Central America and New York between 2014 and 2017, we surveyed male and female Golden-winged Warblers, modeled fall arrival and overwintering occupancy, assessed body condition, and deployed geolocators on select males. Results suggest that sexual segregation is driven primarily by male exclusion of females from high quality habitat in nonbreeding sites, which results in mid- to high-elevation evergreen broadleaf forests being male-biased and lower elevation habitat with less structural diversity being female-biased. The failure to explicitly consider sexual segregation in conservation plans resulted in focal areas that over-represented male-dominated areas, despite greater habitat loss in female-dominated areas. In addition, our data from geolocators showed that Golden-winged Warblers employed a migration strategy that minimized spring migration time and used a previous undescribed stopover region in Guatemala and Mexico – with connectivity and timing being distinct from the Blue-winged Warbler. Overall, our research elucidates the causes and consequences of sexual segregation, highlights the importance of considering nonbreeding ecology in conservation plans, and provides new information to guide Golden-winged Warbler conservation.