Documenting the Source of Reoriented Warbler Migration in the Keweenaw Peninsula

 

For years I have been fascinated with the migration of warblers down the coast of the Keweenaw Peninsula in spring and fall. My first observation of this phenomenon was on the 21

After observing these huge flights of warblers I continued to watch every spring at Bete Grise Preserve when I had the time. Here’s what I’ve learned so far: The north portion of this preserve appears to be an important site in concentrating migratory flocks of warblers (Parulidae) moving west down the south shore of the Keweenaw Peninsula. This occurs because the east-west orientation of the Keweenaw Peninsula shoreline terminates at Bete Grise. Warblers normally migrate at night and long-distance diurnal movements are rare. These daytime flights appear to be a reoriented migration of birds caught over Lake Superior east of the Keweenaw at dawn, toward the interior of the Keweenaw (see map).

However, a number of questions remained that I could not answer with only data from opportunistic counts so, this year I set out to do two longer season surveys of westward warbler flights along the Keweenaw Peninsula. This Spring, I set out to Manitou Island where the warbler flights originate—on a survey sponsored by Copper Country Audubon.  Joe Yougman, Drew Meyer and I counted on 5 days from the 18-22 of May at the narrow west tip of the island and were rewarded with over 5,044 warblers of 22 species, most of which passed on a single movement of 3,122 birds on the 21

 

I now have a better idea of why warblers are showing up in the Keweenaw and the best locations to locate recording devices at Manitou Island and Bete Grise to study their flight calls. Stay tuned...