Early departures: Climate change blamed as tiny Alberta bird alters its migration south

A tiny, insect-eating bird that breeds in Alberta is migrating south early, an altered departure time, which researchers say suggests that climate change has forced the species to adapt. 

New research on the least flycatcher sheds light on how warming weather patterns have changed the way these birds split their time between their summer habitats in Canada and wintering grounds in Mexico and Central America.

The paper, published last month in The Wilson Journal of Ornithology, is the latest in a growing collection of studies illustrating how climate change has altered the migratory patterns of birds.

The study shows that the adult birds of the flock are heading south earlier in autumn — two weeks sooner than they would have 32 years ago. 

The research was done in partnership with the Beaverhill Bird Observatory, the second oldest migration monitoring observatory in Canada.

The observatory, located southeast of Edmonton, has monitored bird populations in the area since the 1980s. 

"Because we have three decades of data, we can look to see if there's any changes in that timing," said Geoffrey Holroyd, study co-author, research scientist and chairman of the Beaverhill Bird Observatory. 

"And in fact, that's what we found. The adults are now leaving a full two weeks earlier than they did 30 years ago." 

The altered pattern in migration for the least flycatcher serves as a warning about the future of thousands of migratory birds, which travel hundreds or thousands of kilometres on their annual journeys, Holroyd said. 

Researchers have already tracked similar migratory changes in other species, including mountain bluebirds and saw-whet owls. 

Scientists believe birds take their cue to leave from a variety of factors, including the sunlight, the weather, and the health of their habitat. But as the climate changes, these delicate calculations are interrupted.

When these critical cycles shift, birds risk falling out of sync with the resources they need to survive, Holroyd said.

Birds that migrate early, for instance, may face deadly storms on their journeys north. Extreme heat during early hatching season may mean its simply too scorching for some young to survive.

Holroyd said researchers believe the least flycatcher may be arriving sooner in the spring, allowing for an earlier departure time.