Plus, banding efforts yield historical firsts in Adams County and the Bahamas
Kirtland's Warblers (Dendroica kirtlandii) are recent colonizers to Wisconsin. The first confirmed nesting in Wisconsin was in Adams County in 2007. The number of males recorded in Adams County since that first discovery has ranged from 7 to 16, with a few birds detected in Marinette and Douglas counties throughout the years. The core Kirtland's breeding population, which was discovered more than 100 years ago, is located in central Michigan and consists of approximately 2,000 singing males. The Michigan population has been on an upward trajectory since the 1990s, aided by cowbird control and habitat management.
Reports from Adams County indicate that 2015 was a very successful year for reproduction in the Kirtland's Warbler population. This year, 15 nests were located at the Adams County site (86% successful), contributing to approximately 34-51 fledged chicks, an increase from 2014, which produced 8-10 fledged chicks. Fifteen males and 14 females were confirmed at the Adams County site with 7 males detected unbanded (they all were captured and banded), along with 7 returning banded males and one returning banded male nestling from the 2014 season. Fifteen nesting attempts were made by 13 pairs, with confirmed re-nesting for two pairs.
Nest monitors also reported a nesting pair in Marinette County which fledged two chicks. Nesting outside of Adams County has only occurred two other times, once in 2009 and once in 2013. With the successful nesting in Marinette County, researchers are hopeful that breeding will continue there in future years.
The banding crew captured and banded seven adult males at the Adams County site, three males in Marinette County and one male in Bayfield County during the 2015 season. In addition, 11 nestlings were banded at the Adams County site. Banding nestlings helps to determine if the young warblers return to the breeding site in subsequent years.
Wisconsin Kirtland's males, some females, 17 nestlings (total from 2014 and 2015 seasons) are banded with their own color combinations, and can be easily recognized whether they are here in Wisconsin on the breeding grounds or in the Bahamas on their wintering grounds.
In March and April 2015, researchers surveyed for Kirtland's in the Bahamas and confirmed Kirtland's Warbler ABPI (color-bands Aluminum, Blue, Purple, Indigo), a nestling banded in Wisconsin in 2014. ABPI was one of four fledglings from the nest of adult male AORB (color-bands Aluminum, Orange, Red, Blue).
AORB was banded in Adams County on June 8, 2008, and aged as a second year. Therefore, he was 7 years old in 2014, making him the oldest known Kirtland's Warbler in Wisconsin. AORB had returned to Adams County every year since 2008 to pair with a female and nest; however, he was not detected at the site in 2015.
Two of AORB's nests were successful, one in 2009 that fledged four young, and one in 2014 that fledged ABPI along with three other siblings. ABPI was not detected at the breeding site this season, but one of its banded siblings (ABPO) did return and was confirmed nesting at the Adams County site.
In total, three Kirtland's males banded in the Bahamas on Eleuthera Island have held territories on the Wisconsin breeding grounds. However, the finding of ABPI marks the first time in history that a Kirtland's banded in Wisconsin was sighted on the wintering grounds in the Bahamas.
The nesting confirmation of ABPO, sibling of ABPI, marks the first time researchers have been able to confirm that a Kirtland's Warbler fledged at the Adams County site returned to the same site the next year to breed.
This article was compiled from past reports with new 2015 information added by Sarah Warner of the U.S. Fish and Wildlife Service and Ashley Hannah (2015 nest monitor). Please visit the Facebook page Wisconsin Kirtland's Warbler Project https://www.facebook.com/WIKIWAProject for pictures and updates from the 2015 Wisconsin Kirtland's Warbler season and visit the USFWS Wisconsin Ecological Services Field office website for nesting season reports http://www.fws.gov/Midwest/GreenBay/endangered/kiwa/index.html
