Habitat change sometimes plays favorites among birds

Habitat change is rarely good for birds, or any animal or insect, but here is a case where it offered at least a temporary benefit.

A few weeks ago I wrote about cowbirds and the problem these nest parasites cause by laying their eggs in a native bird's nest.

I mentioned the particular impact that cowbirds had been having (past tense) on Kirtland's warbler, most of its population located in northern Michigan.

I based my comment on a trip several years ago to see those birds.

Well, habitat changes. The open woods used by the warbler matured enough to become unsuitable for cowbirds. While they were once trapped to reduce the impact on the warbler, the cowbird population has moved on.

So, Kirtland's warbler in 2019 was removed from the federal endangered species list (ESL). The bird's status does come with an asterisk: The warbler is reliant on conservation help — human effort maintains its nesting habitat.

Habitat change will always be a threat. The warbler cannot, like cowbirds, simply pick up and leave. It needs a very, very particular landscape.

The birds build their nests on the ground beneath jack pine trees among grass or other plants like blueberry bushes. The jack pine trees in the nesting area must be just the right height (about 5 to 16 feet tall) and the trees must be spaced to let sunlight through to the ground.

That habitat once was renewed by periodic wildfire. Today, work is being done by volunteers who create and maintain it.

"All the on-the-ground conservation work — harvesting and replanting of trees to ensure there's enough nesting habitat — has to continue for as far as we can see into the future," I was told by William Rapai, executive director of the Kirtland's Warbler Alliance.

As the cowbirds learned, change is ongoing.

Restoration efforts by the Michigan Department of Natural Resources and the U.S. Fish and Wildlife Service are funded by sale of timber from the trees.

Unfortunately, the market for jack pine is low. It costs more to replant than revenue gained from selling harvested trees, Rapai told me.

And there is a question: Will the birds accept these replanted tracts?

The Warbler Alliance is working hard to help people understand why jack pine management has to be continued for a species no longer endangered.

The Michigan population is holding steady, Rapai wrote. There also are small populations of the warbler in Ontario and Wisconsin.

"If we see the population fall below 1,500 pairs the warbler goes back on the ESL," he said.

Rapai told me that there is no talk of managing for Kirtland's warbler in Minnesota, although there is an area south of Duluth that biologists believe could host nesting Kirtland's in the future (Carlton County).

Volunteer habitat restoration ever ongoing might be how we eventually maintain populations of other bird species. We would steadily turn nature back on itself to provide necessary living/nesting conditions in our rapidly changing world.

We've done this for Eastern bluebirds for years. When the natural cavities needed for bluebird nesting disappeared, the North American Bluebird Society and thousands of bluebird enthusiasts provided thousands and thousands of nesting boxes — birdhouses — for bluebird use.

This action made a huge difference for the birds, and will for as long as people maintain the boxes. Another forever commitment. And there are more.

We provide nesting platforms for osprey. We manage woodlands for grouse and woodcock, grasslands for pheasants, quail, grouse and prairie chickens. We introduced trumpeter swans to territory from which they had been extirpated.

If we want those species to survive we can't stop, because we won't stop modifying the landscape, making it unfriendly for animal occupants.

The birds mentioned in this story are iconic or prized for hunting. Thus, we care. In some cases our concern might be altruistic, but mostly we champion favorites and some species for whom a solution is evident and achievable.

There is a blanket solution: Actively support conservation efforts for grasslands, forests, wetlands, jungles — for any and all natural land and efforts to restore natural to our animal vocabulary.

Forever.

Lifelong birder Jim Williams can be reached at woodduck38@gmail.com.

Kirtland's warbler tours

The best time to see the warbler is between mid-May and late June when males are actively singing and protecting their territories. Michigan Audubon and the Michigan DNR have regular tours out of Hartwick Pines State Park, about an hour's drive east of Traverse City. Information can be found at michiganaudubon.org/kirtlands-warbler-tours.

Birders are welcome in the nesting area, but are asked to look for KWs from a distance. Breeding areas are posted with Do Not Enter signs.

A notorious Kirtland's expert

The Kirtland's warbler remote nesting location was discovered in 1903. Research 20 years later by a 19-year-old man named Nathan Leopold revealed the cowbird issue. He was considered the world's foremost expert on the warbler. One year later he and a friend, Richard Loeb, committed one of the most notorious murders of the 20th century.

Cowbird control began in 1971

Biologists began serious cowbird control measures in 1971, warbler numbers indicating possible extinction. Trapping was found to be most effective way to remove the cowbirds from that habitat. Thousands of them were trapped as the program continued.