Warbler Guy, When does Kirtland’s Warbler migrate south? The Kirtland’s Warbler migration is early? Or does Kirtland’s Warbler migrate in fall?

Actually, Jeremy (in Detroit), many of the Michigan-based nesting Kirtland’s Warblers disperse and migrate by July (and no later than August). Look for them in mid-July where they nest in central Michigan counties and you’ll often be out of luck. In fact, their nesting period is a small window of time, typically from their mid-May arrival through the subsequent next six to eight weeks.

Then dispersal may happen before mandatory (or obligate) migration occurs. Think of dispersal as local to short-distance travel away from the nesting area. This interim period involves feeding and molting prior to the Kirtland’s long night-time migration to the Bahama Islands.

Followers of this blog may also know that Kirtland’s Warbler now nest annually in Wisconsin. (See articles from May and June, 2011, below.) Wisconsin Kirtland’s Warbler individuals also usually leave their nesting grounds in July. They, too, eventually migrate to the Bahamas, thereby joining Michigan nesters for the non-breeding season.

How many Kirtland’s Warblers exist? Probably no more than approximately 1,825 to 1,850 males, according to recent combined breeding bird studies that incorporate totals from Michigan and Wisconsin. One annual nesting spot in Ontario also occurs for this federally endangered wood-warbler.