Why do some Red-eyed Vireos not migrate?

Posted on August 17th, 2009 – 9:43 AM
By Jim Williams

The Red-eyed Vireo is a ubiquitous bird species found throughout the eastern United States, across the northern tier of states to Washington and well into Canada. It is one of our neo-tropical migrants, arriving here in the spring to breed, migrating back to South America in late summer. It winters throughout northern South America. However, there is a population of the same species that is equally ubiquitous throughout South America. These birds don’t migrate to North America. They make short seasonal movements in South America, but do not leave the continent. So, why and how did some of these birds make their way, a long way, north while others found suitable nesting habitat for food for young with much less effort? I don’t know. The question came to mind while I was examining the excellent range maps in the book “Field Guide to the Songbirds of South America.” Written by Robert S. Ridgely and Guy Tudor, it was recently published by the University of Texas Press. While I have no plans to travel to South America where this book would be extremely useful, I found the range maps for those of ‘our’ nesting migrants that winter in South America very interesting. Guide books dealing with identification and range of North American birds often show only North American ranges. A peek at their winter distribution in South America is illuminating. The book, of course, covers hundreds of species we never see. It has 760 pages and 256 pages of color plates and range maps for more than 1,500 bird species. It’s yours for $49.95 paperback or $125 hardcover.

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