Habitat loss on the breeding grounds is a major contributor to population declines in a long-distance migratory songbird

Abstract

Many migratory species are declining and for most, the proximate causes of their declines remain unknown. For many long-distance Neotropical migratory songbirds, it is assumed that habitat loss on breeding or non-breeding grounds is a primary driver of population declines. We integrated data collected from tracking technology, community science and remote sensing data to quantify migratory connectivity (MC), population trends and habitat loss. We quantified the correlation between forest change throughout the annual cycle and population declines of a long-distance migratory songbird, the Connecticut warbler ( Oporornis agilis , observed decline: −8.99% yr −1 ). MC, the geographic link between populations during two or more phases of the annual cycle, was stronger between breeding and autumn migration routes (MC = 0.24 ± 0.23) than between breeding and non-breeding locations (MC = −0.2 ± 0.14). Different Connecticut warbler populations tended to have population-specific fall migration routes but overlapped almost completely within the northern Gran Chaco ecoregion in South America. Cumulative forest loss within 50 km of breeding locations and the resulting decline in the largest forested patch index was correlated more strongly with population declines than forest loss on migratory stopover regions or on wintering locations in South America, suggesting that habitat loss during the breeding season is a driver of observed population declines for the Connecticut warbler. Land-use practices that retain large, forested patches within landscapes will likely benefit breeding populations of this declining songbird, but further research is needed to help inform land-use practices across the full annual cycle to minimize the impacts to migratory songbirds and abate ongoing population declines.

Climate‐mediated population dynamics of a migratory songbird differ between the trailing edge and range core

“…Furthermore, populations of many species of birds are declining at the trailing edge of their breeding ranges in the southern Appalachians (Sauer et al, 2017 ), despite wintering in broadly different areas of the Neotropics. Taken together, our results strongly support the hypothesis that climate change on the breeding grounds contributes to local population declines in black‐throated blue warblers, but further research is needed to determine how climate change on the breeding grounds interacts with threats encountered during other seasons to shape population dynamics throughout the annual cycle (e.g., Hallworth et al, 2021 ; Rushing et al, 2017 ; Sillett et al, 2000 ). Understanding the drivers of range contractions of migratory birds in montane regions is critically important.…”

Preserving local biodiversity through crop diversification

“…Thus, one can conclude that neotropical migrants are an important component in bird diversity responding to agricultural land use practices. These may not be surprising in view that Hallworth et al (2021) provide evidence that at least for some neotropical migrants it is habitat loss in the breeding grounds that matter for population declines.…”

Spatial‐temporal shifting patterns and in situ conservation of spotted seal (Phoca largha) populations in the Yellow Sea ecoregion

“…This study systematically revealed the spatial-temporal patterns of the spotted seal population in the Yellow Sea ecoregion based on tracking of individuals and the climatic conditions of the sites where they were monitored. Within the life history, habitat loss during the breeding or wintering season is an important driver of population decline in migratory species (Hobson & Wassenaar 1996;Flockhart et al 2015;Hallworth et al 2021). December, January, and February comprised both the breeding and wintering seasons for spotted seals (Jia & Jian 2015;Fig.…”

“…2015; Hallworth et al. 2021). December, January, and February comprised both the breeding and wintering seasons for spotted seals (Jia & Jian 2015; Fig.…”