Black-Throated Warbler Migration Pattern Affected by Global Warming

The spring migration pattern of Black-Throated Warbler, a songbird that migrates from Canada and Eastern US to Central America has been changing earlier and earlier in recent decades, a study reveals.

Data from the U.S. Geological Survey's Bird Banding Laboratory which archived 150,000 individual records of warblers during their spring and fall migrations from 1966 to 2015 were used. The study team discovered that that the  the birds' spring migration timing has moved earlier over the last fifty years, noting that birds pass through banding sites approximately one day earlier each decade.

The team also studied fall migration, and found that there were no changes in the timing of the peak of fall migration but this takes longer now compared to fifty years ago. The findings on the change in the migration pattern of the warbler have been received in the ornithology community as another effect of global warming.In some species, changes in the timing of migration correspond with changes in environmental conditions, Kristen Covino, an assistant professor of biology at Loyola Marymount University in Los Angeles, and lead author of the warbler study,said.

The average change of one day per decade may not seem like a huge difference, but it is important to consider that change in its broader context. Andrew Farnsworth, a research associate at the Cornell Lab of Ornithology, who was not involved with the new study, likened the change in migration to Christmas day shifting every 10 years. In fifty years, Christmas will be on December 20. Few decades after, Christmas would be Thanksgiving. The study found little variation in the bird's fall migration, but fall migration is longer in recent years.

The study provides valuable insight at the behavioral changes to a common songbird, which may have similar effect to other species. The research is unique that it studied not only fall and spring patterns but also the whole geographic range, Jill Deppe, senior director of the National Audubon Society's migratory bird initiative, said.

The study team noted that their specific findings cannot be linked directly to global warming without studying the patterns concerning long-term climate trends. The findings in the variety of bird's behavior could be signs of major climate-related issues, which may influence the bird's ability to evolve and adapt.

Birds have become an important part of understanding the growing impact of climate change. The change in warbler's migration pattern is not directly linked to global warming, nor does it include temperature and climate data. In the field of ornithology, however, signs of climate change across various researchers are becoming hard to ignore. Birds are very susceptible to changes and are a good indicator of what is happening in their physical environment, Farrow explained.

Ornithologists have drawn a direct connection between birds and climate change in their studies. Last December, a study was reported that birds are getting smaller as global temperature increases. Researchers also noted a dramatic decline of the bird population in the U.S. and Canada since 1970 and included climate change as a culprit in the decline.  The National Audobon Society reported that two-thirds of North American birds are at risk of extinction and point it to global warming.