Several Au Sable River anglers encountered a fellow with a cage full of drab-looking birds in the back of his pickup, and one angler had to ask—“What in the world are you doing with those?”

It turned out he was a US Fish and Wildlife Service biologist who’d been collecting brown-headed cowbirds from traps set within the Jack pine forests of the Au Sable watershed. These nest invaders were slated to be destroyed in order to protect the nests and hatchlings of the most endangered song bird in Michigan, the Kirtland’s warbler.

Cowbirds are lazy, parasitic opportunists—laying their eggs in the nests of other birds to hatch. Larger cowbird hatchlings compete with the warbler young, even pushing smaller warblers out of the nest to perish, so cowbird numbers must be reduced in order to protect the small “Jack pine” warbler.

The Kirtland’s warbler (sometimes called the “Jack pine warbler”) was first identified in 1852 by Dr. Jarad P. Kirtland, a doctor and naturalist of Lakewood, OH, who found one of the warblers on his farm. It remained an oddity for a half-century, it’s natal birth site unknown until 1902, when two anglers on the Au Sable found the birds there and reported it to the University of Michigan, which confirmed the small warbler to be a native of the Au Sable watershed.

The small warbler only breeds and hatches from nests on the ground under groves of Jack pine (Pinus banksiana) ranging in height from 5 to 18 feet. They also seek out areas with ground cover composed of blueberries, bearberry or sweet fern.

The “Grayling Sand” soil type is also important because the warblers nest on the ground and their nests would be flooded if rain water didn’t drain quickly through the porous, sandy soil.

The warbler received great attention over the last quarter-century because of its rarity and need for a very specific habitat. Natural forest fires were the original providers of such habitat; but the advance of white settlers resulted in the clearing of much of Michigan’s natural forests. At first, the warbler benefited from such clearing; however, so did the brown-headed cowbird, which moved in as land opened up following fires and farming.

Once pines reach more than 18 feet in height, their lower branches no longer shelter the nesting areas and their usefulness to warblers is nil; so foresters remove these older trees and provide for new and younger Jack pines to replace them. This is done through clear-cutting, and planting of new Jack pines. These are planted as two-year-old stock from the US Forest Service nursery in Watersmeet in the Upper Peninsula.

“The Forest Service treats 1,700 acres a year for warbler habitat,” said Phil Huber of the Huron National Forest. “The DNR treats 2,000 acres a year. This is necessary because the control of fires that once swept over the land removed the natural reproduction of Jack pine,” he explained. Jack pine seed cones are serotinous and they need heat to open up and release seeds. “Large fires helped create natural re-seeding, but gaining control of wild fires stopped that process.”

Without the fires, Jack pine habitat declined as did warbler numbers. The number of Kirtland’s warblers had been reduced to as few as 167 in 1974. A similar low was recorded again in 1987, when extinction seemed likely.

But man’s ability to create new and consistent habitat has brought the “bird of fire” back. In 2008, an all-time record high survey count showed 1,792 warblers, a number that the U.S. Fish and Wildlife Service says moves it close to being removed from the endangered species list.

The expanding warbler population found pockets of suitable habitat in a few new locations in Wisconsin, Ontario, and in the Upper Peninsula, where a count of 24 warblers was made in the Hiawatha National Forest. They have also spread west in the state, where biologists now monitor several warbler sites in Clare County.

“The birds migrate each year to winter in the Bahaman Islands, where their habitat and foods are being studied. We now bring a Bahamian student to Michigan to study the bird’s habitat and management practices here, and then returns to study the bird’s habitat and foods there, adding to our knowledge,” said Huber.

When the warblers return to Michigan each May, the males arrive first. This year, they arrived a week earlier. The females arrive a little later and males sing over a territory they stake out, aggressively defending it against others, though the bird overall forms colonies in fairly close approximation to others.

In order to protect the nesting birds, closure of habitat areas to public entry is made for the nesting period. But in order to allow birders, science students, and others from the public to hear or possibly see the warblers when the birds are nesting, controlled guided tours are offered out of Grayling and Mio.

As fall nears, the long return to the Bahaman Islands begins for these native “Jack pine warblers”—their song not to be heard again until May returns to the Au Sable valley. It’s a sweet song worth the wait. YouTube video