Tuesday, October 6, 2015

The Navarre / Blackpoll Warbler Connection

Weather has really been a big story for migration this fall. A high pressure sitting over the Great Lakes the last third of September has stalled movement through the region. Other reports indicate a major movement off the western side of Lake Superior which may be a result of all the northeast wind we have encountered. Little early presence of the typical October species has occurred except for Winter Wren, with more than 10 banded in late September.
Navarre has been the site of many returning BLPWs during the fall migration season over the years, and this year is no exception. As of the first of October, we have encountered two Blackpolls previously banded in 2014. One was a Hatching Year (HY) bird banded on September 20, 2014 and captured again on September 27, 2015 as an After Hatching Year (AHY) male. The other Blackpoll was banded in Navarre on October 3, 2014 and returned to the same stopover site on September 28, this year.  This puts great emphasis on the value of the Lake Erie Marsh region, arguably the most important stopover site for migrating Blackpoll Warblers in fall. 

Fall Blackpoll Warbler 
A big question has always centered on how many birds migrate through any area. While this is extremely difficult to determine for songbirds, the Blackpoll recaptures have offered a small window into this important question. Accepting a few very big assumptions, we have used the simplest of mark-recapture analysis tools (the Lincoln Index) to assess that volume. So far, using the recaptures, the number banded last year, and the number banded this year a point estimate of ~ 340,000 Blackpolls have passed along the beach ridge of Navarre this fall. Applying an approximate figure for the percentage of the stopover habitat Navarre represents to the marsh region, and you come up with nearly 7 million of these winged wonders visiting the Warbler Capital of the World so far this fall.

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