Monday, September 1, 2008
UPDATE: Kirtland’s Warbler 2008 Breeding Success in Wisconsin and Michigan
© photo from U.S. Fish and Wildlife Service
As many of you may already know (and per my earlier posting below from June 27 and July 8, 2008), the Kirtland’s Warbler (Dendroica kirtlandii) is one of North America’s rarest neotropical migrant songbirds.
As brief background, the species was not discovered to breed in Michigan until 1903 when Norman A. Wood discovered the first nest in Oscoda County in northern lower Michigan. Until 1996, all nests were found within 60 miles of this site. Since then, a small number of nests have been found each year in Michigan's Upper Peninsula. Until last year, only periodic nesting occurred in Wisconsin and the province of Ontario.
But 2007 and 2008 changed everything. Successive discoveries during the last two breeding seasons of Kirtland’s in similar locations (and a new Wisconsin County added in 2008) have changed the boxscore appearance. It’s arguably now safe to suggest that Kirtland’s nests annually in both Michigan and Wisconsin.
What follows provides an update and summary of the species’ 2008 breeding success in Wisconsin. The chart, below, provides an update of totals for Michigan, Wisconsin and Ontario in 2007 and 2008.
Wisconsin’s documented Kirtland’s total in 2008 is 10 (with 9 out of the 10 banded and fitted with colored bands to, hopefully, monitor their presence in future breeding seasons if and when they return to North America next spring). Five nests were observed in Adams County (central WI) while two different singing males were heard in Marinette County (northern WI).
In all, volunteers and professional biologists monitored 12 Wisconsin counties for Kirtland’s in 2008. Beyond Adams and Marinette Counties, survey teams reported hearing or seeing Kirtland’s at several sites in Vilas and Jackson Counties. Ensuing confirmation by US Fish and Wildlife and WI DNR biologists of these reports was not possible.
(# = In addition, another Kirtland’s male was reported from a far northern WI county – Bayfield – and the female associating with the male was also seen. However, no additional sightings were repeated and a nest was never found, so it remains uncertain as to whether breeding occurred at this site.)
Meanwhile, reports from the US Fish and Wildlife Service’s monitoring biologists in Michigan suggest fair success among this season’s resident breeding population in six north-northcentral counties that totaled 1,791 singing males –- an increase of 94 in comparison to the 1,697 singing males reported in 2007.
The combined total of singing males heard throughout Michigan, Wisconsin, and Ontario in the 2008 breeding season was 1,801 males (see below "chart" that breaks down the breeding numbers for these areas.)
(Interestingly, as a digression of thought while you read this account, note that all of the Kirtland’s have currently dispersed and/or migrated south en route to their Bahama Island non-breeding grounds. Undoubtedly, some of the early migrants that left Wisconsin and Michigan by the first week of July may have already arrived on their non-breeding territory within the Bahamas.
Whether other individuals, in addition to other migrating bird species, survived such calamities as Gustav, obviously remains unclear. It’s safe to suggest, however, that mortality is a dominant result of songbird migration, with estimates ranging from 30 to 50 percent mortality.)
Kirtland’s Warbler 2007 Breeding 2008 Breeding
Wisconsin 8 males
(3 nest sites in one county) 10 (two counties)
(# above remark = three?)
Michigan 1,697 males 1,791 males
Ontario 2 males 1 male
(and thanks for their help) that I used to create this post:
Tom Schultz, Dr. Noel Cutright, and The Northeast Wisconsin Birder, Volume 7, Issue 5, June-July, 2008