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Preliminary results of the 2013 breeding season indicate that 9 pairs of Kirtland’s warblers made 12 nesting attempts at the Adams County sites. At least 4 nests fledged 13 young. Eight nests failed, most likely due to predation, including two nests that had been parasitized by brown-headed cowbirds. Because we did not approach nests, the total number of parasitized nests is not known. All of the successful nests, however, fledged Kirtland’s warbler offspring and no cowbird young.
We received special help with identifying a male from Frank Boll, award winning videographer now retired from Wisconsin Public Television. A previously banded male had lost a color band from each leg, which prevented us from identifying him with certainty. The banding crew attempted to recapture this bird in May in order to read the number on its aluminum band, but the capture was not successful.
Frank, who was filming migratory songbirds for Sumner Matteson of the DNR, offered to use a high-powered Swarovski spotting scope used in filming to read the band numbers from a distance. Nest monitor Valarie Michel escorted Frank to the bird’s territory on June 12 and used a playback recording of a male Kirtland’s warbler song to draw the male in close. Although Frank could not see all the numbers, he was able to report combinations of numbers and their positions on the band. After comparing Frank’s numbers to our banding and nest monitoring records, we are fairly confident that this male was banded in 2008, our first year of banding at the Adams site. This bird returned to Adams County in 2009 and 2010, was most likely a bird found in 2011 with one band missing from the left leg, and probably the same bird found last year with a band missing from each leg. Many thanks to Frank for sharing his time and skills with optical equipment to document the male.
Jack Swelstad, a volunteer surveyor, and Daryl Christensen, nest monitor, took turns visiting the territory of a 4-yr-old male in Marinette County. A female was observed leaving a nest with 3 eggs on June 17. Unfortunately, the nest was found empty on June 26, too soon for young to have fledged. It is uncertain whether a second nesting attempt was made. Adults, however, were no longer present at the site on July 13, making it unlikely that nesting was successful for this pair.
Very few reports were made of birds outside of Adams County this year. Jack Swelstad found two males in Marinette County: one male banded in 2011 was found on his same territory for the third consecutive season (see nesting report above); a second unbanded male was located about 10 miles from the banded bird.
DNR biologist, Steve LaValley, kept up his record of annually reporting a Kirtland’s warbler. This one was unbanded in Douglas County at a site where folks from UW –Superior also heard a male singing on a different day according to Steve.
Only one unconfirmed report was made this year and it was from Bayfield County.
Ron Refsnider and a banding crew consisting of Joel Trick, Daryl Christensen, Kelly Vanbeek of USFWS, and Jack Swelstad, successfully captured and banded the second Marinette County male on June 11. Hoping to band the Douglas County bird, Ron tried to re-locate it on June 22 with no luck. Interestingly, two males were heard singing in a new area in Adams County on June 20. One of the birds, still singing in the new area on June 24, was determined to be unbanded and thus a new bird at the site. The other bird was never identified. Given last year’s occurrence of a bird from Bayfield showing up late in June at the Adams site, it is possible that this male was actually the missing Douglas bird. It was not captured or banded. Ron, Joel, and the nest monitors are attempting to capture and band fledglings at the Adams site this week. We hope that this effort will allow us to document fledglings returning to Adams County next year.
Cowbird traps were removed shortly after July 1 following 11 weeks of trapping. Barry Benson of APHIS Wildlife Services, Inc. will submit final tallies later this month.