Quantifying drivers of population dynamics for a migratory bird throughout the annual cycle

Abstract

Worldwide, migratory species are undergoing rapid declines but understanding the factors driving these declines is hindered by missing information about migratory connectivity and the lack of data to quantify environmental processes across the annual cycle. Here, we combined range-wide information about migratory connectivity with global remote-sensing data to quantify the relative importance of breeding and non-breeding environmental processes to persistent long-term population declines of a migratory songbird, the wood thrush (Hylocichla mustelina). Consistent with theoretical predictions about population limitation of migratory birds, our results suggest that habitat loss and climate have contributed to the observed declines in wood thrush breeding abundance, yet the relative importance of breeding versus non-breeding factors is population-specific. For example, high-abundance core breeding populations appear to be more limited by habitat loss, whereas low-abundance, peripheral populations appear to be limited by climate-driven seasonal interactions. Further, our analysis indicates that the relative impact of breeding habitat loss is at least three to six times greater than the impact of equivalent nonbreeding habitat loss and therefore the steepest regional declines have likely been driven by the loss of breeding habitat. These results underscore the need for population-specific conservation strategies implemented throughout the annual cycle to reverse long-term declines.

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

“…Our increased understanding of migratory connectivity for this species provides investigators with an opportunity to design studies that quantify the relative importance of the characteristics of different breeding and wintering areas that may be contributing to population declines (Rushing et al. ). Such studies are especially needed for Golden‐winged Warblers in the Appalachian Mountains, where breeding populations have experienced a drastic decline over the past several decades (Rosenberg et al.…”

“…, Rushing et al. ). Researchers now have the opportunity to inventory and quantify those demographic parameters that are still needed to attempt full life cycle modeling for this species (i.e., non‐breeding season survival), and to then build population models that consider patterns of migratory structure.…”

Habitat‐dependent occupancy and movement in a migrant songbird highlights the importance of mangroves and forested lagoons in Panama and Colombia

“…Conservation of migratory species is challenging because their shifting distributions make it difficult to identify the potentially diverse factors limiting populations at different points throughout the annual cycle (Marra, Cohen, Loss, Rutter, & Tonra, 2015;Runge, Martin, Possingham, Willis, & Fuller, 2014;Webster, Marra, Haig, Bensch, & Holmes, 2002). This is especially problematic for the overwintering period, which often encompasses the largest portion of the annual cycle and is generally when the most challenging environmental conditions are experienced (e.g., tropical dry season; Rushing, Ryder, & Marra, 2016;Smith, Reitsma, & Marra, 2010).…”

Using citizen science monitoring data in species distribution models to inform isotopic assignment of migratory connectivity in wetland birds

“…Knowledge of migratory connectivity informs conservation by associating populations with habitats that they use throughout the entire year. Connecting populations and habitat throughout the annual cycle is essential for identifying limiting factors and can permit more effective responses to threats (Norris and Taylor , Taylor and Norris , Rushing et al ). Most studies examine migratory connectivity between wintering and breeding areas, but links of migratory stopover habitat is also important in understanding factors that limit populations throughout their annual cycle (Hobson et al , ).…”