Backpacking birds shed light on conservation risks facing vulnerable Blackpoll Warblers

Blackpoll Warblers are one of the fastest declining North American songbirds, with the species having experienced an annual decline of 2.3% since 1970.

Songbirds carrying backpack geolocators have shown that habitat loss in two key migration stopover sites for Blackpoll Warblers could create serious conservation risks, says new research co-authored by Wildlife Conservation Society Canada scientists in the Yukon, and partners from the University of Guelph, Birds Canada, and National Audubon Society.

Blackpoll Warblers are one of the fastest declining North American songbirds, with the species having experienced an annual decline of 2.3% since 1970. These tiny songbirds breed in North America’s treed boreal wetlands before undertaking an epic return-trip migration upwards of 20,000km, including a transoceanic leg to and from wintering areas in South America.

The study, published in Nature – Scientific Reports, tracked the migration of 47 individuals from 11 sites across the breeding range, including in southern Yukon and northern British Columbia, using geolocators. These devices store data in a tiny backpack carried by each bird for a year until they return to their breeding territories.

Data highlights the importance of New England and the mid-Atlantic regions as critical stopover sites for refuelling during migration. Protecting breeding habitat in the Yukon is also a vital component of full-life cycle conservation efforts.

“These tiny songbirds – the weight of 2 Canadian loonies – undertake astonishing migrations between breeding territories in the boreal and wintering areas in South America, including record-breaking transoceanic flights. With this collaborative study stretching from Alaska to Newfoundland, for the first time, we can not only link breeding populations with specific wintering areas but also identify migration routes and two key stopover sites.

“Migrating blackpolls, like all songbirds, are at risk from habitat loss, building collisions, and other human threats. When an entire breeding population depends on just a couple of areas for resting and refueling during migration, that risk is concentrated. However, this knowledge also unlocks a critical tool in recovery of declining migratory birds – protecting habitat and preventing human-caused mortality at each stage and location of a population’s migratory cycle.” - Hilary Cooke, Co-Director of WCS Canada’s Northern Boreal Mountains program, and co-author of the study

The study also documented a potential new record in bird migration, with an individual from a breeding population in Newfoundland travelling 4100km in 84 hours to northern Venezuela.