American Robin migration happening earlier

Robin migration
At the northern reaches of its breeding range, American Robin is migrating five days earlier per decade, scientists report. Photo by Dee Carpenter Originals/Shutterstock

Scientists have published a number of notable papers in recent months that further enhance our understanding of bird migration. Here are three examples:

American Robin

In northern Alberta, American Robins are responding to climate change by migrating five days earlier per decade in spring than they did in the early 1990s, according to a study in Environmental Research Letters.

“It’s not entirely surprising that robins appear to be migrating through boreal Canada earlier because other studies have found that many bird species are adjusting their migration timing,” says lead author Ruth Oliver. “However, our study suggests that robins are able to adjust their migration timing by responding to environmental cues along the way, primarily snowmelt. This suggests that robins may be able to keep pace with the rapid environmental change occurring at high northern latitudes.”

Bobolink

A study of Bobolinks using light-level geolocators reinforced scientists’ understanding of a migration corridor from the eastern U.S. to central South America. The northbound and southbound routes largely overlap, and the birds’ departure dates and the duration of southbound migration vary by breeding population.

Rosalind Renfrew and her co-authors, writing in the Wilson Journal of Ornithology, also report that birds from all breeding areas arrive at a migratory stopover site — the Llanos grasslands of Venezuela and Colombia — within a few weeks of each other. They remain for three to six weeks before crossing the Amazon Basin to eastern Bolivia, Paraguay, and northeastern Argentina.

Black-throated Blue Warbler

A study of 50 years of data on the Black-throated Blue Warbler shows that early spring migrants passed through sites about 1.1 days earlier per decade.

“Overall, we found that not only was the peak of spring migration occurring earlier, but the earliest individuals also migrated earlier,” write Kristen M. Covino and colleagues in The Auk. “While the peak timing of fall migration has not changed, the earliest individuals are migrating earlier and the latest individuals are migrating later.”

This article appears in “Birding Briefs” in the July/August 2020 issue of BirdWatching magazine. 

More stories about discoveries made with light-level geolocators

Study: Nearly all Prothonotary Warblers winter in northern Colombia

Connecticut Warbler’s epic autumn migration

Study: Population trends of Golden-winged Warbler tied to wintering regions
 

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