Tuesday, May 24, 2011

Kirtland's Warbler: Not Michigan's State Bird

The state bird of Michigan is the American Robin (Turdus migratorius). That’s all well and good, but a lot of bird admirers in this state think it would make more sense to bestow that honor upon the Kirtland’s Warbler. After all, the vast majority of these birds choose Michigan – and nowhere else - as the site for their summer nests. A handful (almost literally) call Wisconsin, Minnesota, and Ontario home, but those numbers are negligible compared to Michigan. That’s not to say there are millions of them here. Last year’s census counted only 1773 singing males in the jack pine forests of the northern Lower Peninsula of Michigan. Kirtland’s Warblers are protected under the Endangered Species Act, and with the assistance and cooperation of several agencies, the bird has recovered from a population of only a couple hundred pairs in the 1980’s.

Young Jack Pine habitat in Huron-Manistee National Forest, Michigan

Kirtland’s Warbler utilizes the Jack Pine (Pinus banksiana) forests as nesting habitat. Pure stands of young jack pine are essential, as the warblers sing from atop trees that are between roughly 5 feet and 15 feet tall. The nests are built on the ground near the base of a tree, log, or other debris. Loss of habitat has been devastating to Kirtland’s Warblers, particularly that caused by suppression of wildfires that lead to a constant supply of pure stands of young pine. Today the US Forest Service manages for proper warbler habitat by planting Jack Pine plantations, conducting prescribed burns, and clear-cutting of selected mature pine forests. The warbler nesting grounds are closed to entry during breeding season, though the USFS and US Fish and Wildlife Service provide tours that virtually ensure a good spotting of a Kirtland’s Warbler.

Kirtland's Warbler (Dendroica kirtlandii)
Kirtland's Warbler (Dendroica kirtlandii)

An actual good picture of a Kirtland's Warbler courtesy of Bmajoros under a Creative Commons License.

Take a Tour
On a Kirtland’s Warbler tour you can expect to walk along a sandy forest service road listening for the melodic call of the warbler. Nashville Warblers (Vermivora ruficapilla) or Canada Warblers (Wilsonia Canadensis) may give a false alarm, but sooner or later, you’ll spot a Kirtland’s happily singing from atop a tiny pine. Like all warblers, they have a tendency to bounce around, but on the nesting grounds it’s not unusual for one to sing in one spot for several minutes. On our excursion this week we had plenty of time to point the scope at one male and watch him for a few minutes. Binoculars will be fine for most sightings, but if you have a scope, by all means take it along. The guides will often have scopes, but it never hurts to have your own equipment. As with any warblers, good photography will require a very long tripod-mounted lens and a bit of good luck. My shots are serviceable but certainly not quality.
The Dreaded Cowbird
One other threat to Kirtland’s Warblers is the expanding populations of the nest parasite Brown-headed Cowbird (Molothrus ater) that lays eggs in other birds’ nests after which the hatchling cowbirds overpower and kill some, if not all, of the resident hatchlings. In its traditional range, this parasitism is of little consequence to native birds. Cowbirds, however, are a recent addition to the forests of northern Michigan, having taken advantage of the massive clear-cutting of the last century. In order to manage for survival of the Kirtland’s Warbler, the US Fish and Wildlife Service traps Brown-headed Cowbirds at more than 50 sites throughout Kirtland’s habitat in the Huron National Forest. The cowbird removal appears to have helped warbler populations significantly.
Ecology, Ecology, Ecology

As with everything in nature, there’s more to the story than just the pines providing a spot for the warblers to live. The Jack Pine forests harbor a pine predator, the Jack Pine Budworm (Choristoneura pinus), a needle-eating Lepidopteran (caterpillar). During their breeding season, Kirtland’s Warblers have been shown to eat enormous quantities of these caterpillars, particularly when feeding their young. As Bay-breasted Warblers (Dendroica castanea) are known to do across the north with Spruce Budworm, it seems D. Kirtlandii is a natural control for Jack Pine Budworm.

Tours can be arranged through the US Forest Service from Mio, Michigan or the US Fish and Wildlife Service from Grayling, Michigan. On my tour, I was graced with guides from both of those agencies as well as the Michigan DNR. Thus I can’t speak to which tour would be better, but I doubt you can lose either way.

In Grayling you can even stay at the Warbler's Way. (I haven't stayed there; can't offer a review.)
In the interest of not ignoring the home of the Kirtland’s Warbler for most of the year, the Bahamas are a fairly nice spot to visit in January! Just as their summer breeding range is severely limited compared to that of most wood warblers, they winter only in the Bahama Islands, primarily on Eleuthera Island.  Eleuthera is over a hundred miles long and never more than a few miles wide. What “interior” there is has some pine forests and deep within these trees is where you’ll find (if you’re really looking) the Kirtland’s Warbler in winter. Eluthera is not as heavily developed as the inner Bahamas and makes for a great nature escape in winter.
Below are links to two great books and a nifty stuffed warbler (not a real one!)

No comments:

Post a Comment