Monday, December 14, 2015

The Kirtland’s Warbler: An Endangered Michigan Songbird

Maggie Dollar, Youth and Education Intern, Thumb Land Conservancy


Introduction
Bill Collins, Executive Director

Back in the summer when biology professor Carrie Dollar helped the TLC get its first student interns from Saint Clair County Community College, she told us that her daughter, Maggie, was also interested in helping the TLC. She wanted to write some nature articles for the TLC, and we were happy to accept her offer. Maggie is an exceptional writer, especially considering that she’s only in the eighth grade at Parcell’s Middle School in Grosse Pointe where she is taking all honors courses and participates in a journal club. Maggie is not only a writer, but plays the cello and is on her school’s robotics team. She aspires to become a paleontologist or archaeologist because of her interest in history.

We hope we will see more of Maggie’s writing. Her first article is about the Kirtland’s Warbler, a migratory bird that breeds in northern Michigan, and seems to be recently expanding its territory. As do many warblers, likely a few Kirtland’s pass through the Thumb on their way to and from their winter range in the Bahamas, but sightings in our region have been extremely rare and it’s thought they largely make their migratory journeys as non-stop flights. Regardless, with so few Kirtland’s Warblers, every one counts and so if the Thumb provides habitat for the odd bird that occasionally stops in our area, all the better. Also, what we learn about a species that may not normally inhabit our region can provide insight into species that do. Instead of focusing on boundaries and limits, one thing nature teaches us is how connected everything is.


The Kirtland’s Warbler: An Endangered Michigan Songbird
By Maggie Dollar

The Kirtland's warbler, or Jack Pine warbler, is a songbird that only nests on the ground near young jack pine trees, mostly in the northern part of Michigan’s Lower Peninsula. In the fall, they migrate south to their wintering grounds in the Bahamas. The bird is about the size of a large robin, from five and a half to six inches (fourteen to fifteen centimeters). Its back is grey with black marks and its stomach is a bright yellow.

Female Kirtland's Warbler
"Kirtland's Warbler - female" by Dominic Sherony - Kirtland's Warbler female.
Licensed under CC BY-SA 2.0 via Commons - https://commons.wikimedia.org/wiki/File:Kirtland%27s_Warbler_-_female.jpg#/media/File:Kirtland%27s_Warbler_-_female.jpg

Male Kirtland's Warbler
Photograph by Ron Austing.
Olson, J. A. 2002. Special animal abstract for Dendroica kirtlandii (Kirtland’s warbler).
Michigan Natural Features Inventory, Lansing, Michigan. 5 pages.

The Kirtland's warbler is one of the rarest members of the wood warbler bird family. The only places it currently nests are mainly in Michigan, and a few locations in Wisconsin and the province of Ontario. The first Kirtland’s warbler in North America was identified in 1851 from a specimen collected on Dr. Jared Kirtland’s farm near Cleveland, Ohio. Biologists did not learn where it nested until 1903 when they found a warbler nest in a jack pine forest in northern Michigan. Today, Kirtland’s warbler sightings are rare, mostly because they face two main threats: lack of crucial young jack pine forest habitat and the parasitic brown-headed cowbird.

Kirtland's Warbler county occurrences in Michigan
Michigan Natural Features Inventory. 2007. Rare Species Explorer (Web Application).
Available online at http://mnfi.anr.msu.edu/explorer [Accessed Dec 14, 2015]

Many people do not realize that birds can also be parasites! The parasitic cowbird is a major threat to Kirtland’s warblers. A female cowbird will lay its own eggs in the nest of another bird, such as a Kirtland’s warbler. The cowbird egg hatches before the warbler eggs, getting a head start on growth. The young cowbird is bigger and able to claim more food than the warbler nestlings, and the cowbird may even push the baby warblers out of the nest!

Another factor that endangers the Kirtland’s warbler is its selective nature about where they nest and the fact that they do not like to share their nesting area with other warblers. The Kirtland’s warbler requires about thirty to forty acres for nesting and raising their young, which has become a problem, as there are not enough dense areas of young jack pine.

Kirtland's Warbler habitat - Young Jack Pine in northern Michigan
Olson, J. A. 2002. Special animal abstract for Dendroica kirtlandii (Kirtland’s warbler).
Michigan Natural Features Inventory, Lansing, Michigan. 5 pages.

Realizing the Kirtland's warbler was in danger of becoming extinct, forest managers set aside special areas for them. In these special Kirtland's warbler management areas, forest managers try to imitate what once happened naturally that allowed young jack pines to prosper. Oddly enough, forest fire prevention has led to the decline in young jack pine forest. Sometimes carefully managed fires are set purposefully in small areas of old jack pine in order to clear the way for young jack pine. In other areas, forest managers harvest some of the old jack pine trees, replanting the areas with jack pine seedlings. At least 1,200 seedlings are planted in each acre to create good nesting conditions. Essentially, good management of the bird is rooted in jack pine management.

The requirements for nesting and the cowbird parasite have caused a dramatic decline in Kirtland’s warbler population and has led to the listing the species as “endangered” since 1967.

Kirtland's Warbler occurrences in Michigan counties
Michigan Natural Features Inventory. 2007. Rare Species Explorer (Web Application).
Available online at http://mnfi.anr.msu.edu/explorer [Accessed Dec 14, 2015]

If you are interested in seeing the Kirtland’s warbler, the Huron-Manistee National Forest hosts Kirtland’s warbler guided tours. The best time to visit is May. For more information on the tour visit the U.S. Fish and Wildlife website at: