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Wednesday, May 12, 2021

Evening Grosbeaks, where are they?

Where are the Evening Grosbeaks now? Evening Grosbeaks are part of this historic 2020-2021 superflight irruption of winter finches and have been seen in big numbers in various places. Evening Grosbeak populations may have been fueled by the large spruce budworm outbreaks in the eastern boreal forest, the outbreaks made larger by lack of spraying for budworm control due to the Covid pandemic. Evening Grosbeaks thrive on the budworms during breeding, and once the budworms went dormant for winter, the grosbeaks fled south with the other irruptive finches. In the fall, there were day counts of 100s to 1300+ Evening Grosbeaks moving southwest along the Great Lakes shorelines in Ontario. This Evening Grosbeak irruption was one of the largest in several decades, and birds in the eastern part of the country made it as far south as Florida and Arkansas.
See the eBird map for Evening Grosbeak from October 2020-May 2021. They are returning through about mid-May into June to their breeding ranges, so watch for them at your sunflower feeders.
Once considered rare east of the Rockies and Mississippi River, Evening Grosbeak’s expanded their range in the early 1900s into eastern North America. This was aided by the large-scale planting of Box Elder trees, a favorite food, which holds seeds through winter, allowing the grosbeaks to winter and even breed. The peak of wintering Evening Grosbeaks was the 1940s to the mid-1980s, with significant declines since. In 2016, an Evening Grosbeak population trend assessment revealed a continent-wide decline of 92% since 1970 – the steepest among all land birds in the U.S. and Canada. This led to the national listing of the species as Special Concern in Canada (COSEWIC 2016).
A multi-year study, by David Yeany at the Pennsylvania Natural Heritage Program at the Western Pennsylvania Conservancy is using new Motus tag tracking technology to better understand the migration ecology, and perhaps the decline, of Evening Grosbeaks. The tracking information is beginning to link winter populations of Evening Grosbeaks to breeding areas with active spruce budworm outbreaks in the boreal forest. So stay tuned, keep your feeders filled with sunflower, and you may see the return flight.

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