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Adams County Report
We are now in the midst of nesting season at our Adams County Kirtland’s warbler sites. The cold and wet weather that has plagued our Wisconsin spring has undoubtedly made it difficult for many nesting birds, including Kirtland’s warblers. To date, monitors Sam and Caitlynn have been able to locate eight nests, though we may find one or more additional nests after they hatch, as they are much easier to locate when both parents are bringing food to the nest.
So far, we have already seen five nesting attempts end prematurely, with the cause for failure largely unknown. In at least one case, there is strong reason to believe that the heavy rain and cold temperatures contributed to the death of a whole brood, only days before their expected fledge date. Following the poor nesting success we observed last year, we have taken a very conservative approach, and in general have not approached any active nest closely. In part due to this conservative monitoring, we have limited information on some nests that failed prior to their expected fledge dates. One nest was found to have successfully fledged today, with at least one Kirtland’s warbler fledgling being tended by adults. This nest was apparently further along than we thought when it was discovered. Of the two nests currently known to be active, both are apparently still incubating.
The unbanded male that Caitlynn discovered about two weeks ago at our satellite Adams County site disappeared from this location early this week, about the same time that an unbanded male showed up at our main site. We suspect this is the same bird, but cannot know for sure. If he moves again we will now be able to track him, as we successfully captured and gave him his own color band combination on Wednesday of this week. This is the fourth new male Kirtland’s warbler we banded in Adams County in 2011.
Douglas and Marinette Counties
Over the past few weeks, single male Kirtland’s warblers have been documented at one site each in Douglas and Marinette Counties. Caitlynn’s observations of the Marinette County male in early June did not detect the presence of a female. For the past few weeks, we have made the monitoring of Adams County nests a higher priority, but plan to check on the Douglas County male this week to see if any female may be present.
Each year since 1971, Michigan has conducted an annual census of singing male Kirtland’s Warblers. And every year, we now also report Wisconsin totals for inclusion in the census. In 2011, we documented a total of 21 male Kirtland’s warblers in Wisconsin during the official census period of June 6-20. This total includes 19 males known to be present during this period in Adams County, and single birds in Marinette and Douglas Counties.
There were several other confirmed sightings of Kirtland's warblers in Marinette and Bayfield Counties, but they fell outside of the census period, and could have been sightings of the same birds listed above. We also had another color-banded male in Adams County earlier in the season, but he was not observed during the census period. In 2010, the Kirtland’s Warbler Annual Singing Male Census total was 1,773.
Cowbird trapping at our main Adams County site has now ended for the year. In response to our delayed spring and low trapping totals, we extended our trapping period this year, in an effort to provide maximum protection from nest parasitism for nesting warblers. USDA-Wildlife Services operated three cowbird traps at the Adams County site from April 18 through July 1. Wildlife Specialist Barry Benson reports the capture of another 9 brown-headed cowbirds over the past two weeks, bringing the season total to 166 over 11 weeks of trapping. This compares to a season total of 216 captured through 9 weeks of trapping in 2010, and 303 for the same period in 2009.
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