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Wisconsin Kirtland's Warbler Update
June 5, 2009
This week, most Kirtland’s warbler females are building nests and laying eggs. Male singing activity has become more intermittent and limited, as they become less vocal when paired with a female, and more secretive during the laying period. Nick has been able to confirm several eggs in at least one of the nests. There has also been at least one new arrival and possibly a shift in territory since the previous update, with one male no longer occupying the area he had previously, and two unbanded males found in new territories. One of the new males was discovered just today, and is already paired with another female. This brings the total number of Kirtland’s warblers at the Adams County breeding site to at least nine males and eight females.
We kicked off our 2009 banding efforts on Monday June 1, with the arrival of our volunteer bander Ron Refsnider. Nick was able to guide us to each of the males territories, and we began by targeting the three unbanded birds that Nick had identified over the past several weeks. Marking these birds with their own color bands will allow Nick to more effectively map their individual territories and greatly facilitate monitoring.
In short order, we were able to capture two of the unbanded male Kirtland’s warblers located around the periphery of the banded males territories, and gave them each a new set of color bands. However, when we went for the third bird, he was nowhere to be found. After several fruitless searches, we turned our attention to the other birds at the site.
At the request of the Kirtland’s Warbler Recovery Team, this year we collected feather and toenail samples from each of the birds we captured. These samples are to be used for isotope analysis to assist in determining the potential linkage between the habitat quality of the wintering grounds and the breeding grounds.
We attempted to recapture each of the five banded males known to be present, to gather data on their plumage and physical condition, and collect samples for isotope analysis. As the winds picked up it became more difficult for the birds to hear the recording used to lure them in, and also made the mist nets used for capture more visible. Several birds were quite elusive, and refused to enter the net. By the end of the first day, we had managed to capture three of the five banded males present. As a bonus, we also captured the female paired with the Bahamas-banded male, and she became the first female Kirtland’s warbler ever banded in Wisconsin.
We began again early the next day, and made another try for the two birds that had managed to avoid capture the day before. After numerous tries and several close calls, we decided that one bird was not going to be caught this day, and we gave up on him. Moving on to the other banded bird, we managed to capture him fairly quickly. We ended our first Adams County banding trip of 2009 having captured six males and one female Kirtland’s warbler, with two of these males being newly captured, previously unbanded birds.
We then decided to travel to northern Marinette County to make a try for a bird that was reported there just the day before. After the four hour drive, we were glad to quickly find the bird, and after waiting for some time for the bird to respond, we were rewarded with the successful capture of another banded male. This individual was not the same bird found at this site in 2008, but rather a new bird that was banded on Eleuthera in the Bahamas just two months ago, on April 3, 2009.
Anyone seeing a color-banded bird is asked to report their sighting to either Joel or Kim using the e-mails and numbers below. Band combinations are described in the following sequence, referencing top and bottom bands, left and right legs: Top left/bottom left, top right/ bottom right. All birds receive a standard aluminum, numbered band, plus three colors, which may include: Indigo (dark blue), Light Blue, Orange, Jet (black), Yellow, Red, Green, and Purple.
USDA Wildlife Specialist Barry Benson reports that over the past week, he removed an additional 24 cowbirds from the three cowbird traps. Through June 5, a total of 272 cowbirds have been captured and removed from the traps at the Adams County Kirtland’s warbler site.
The annual Kirtland’s Warbler census in Michigan is conducted from June 6-15, and we encourage Wisconsin volunteers to conduct their surveys during this period, to allow the inclusion of any Wisconsin birds in the comprehensive census. Volunteers will begin their searches in earnest tomorrow, June 6. Anyone finding a Kirtland’s warbler is asked to contact either Joel or Kim at the e-mails and telephone numbers listed below.