The Case of the Disappearing Lark Decoys

A streaked horned lark decoy (photo: Hannah Anderson)Biologist Hannah Anderson of the Center for Natural Lands Management (CNLM) had a mystery on her hands. Conducting an experiment to see if she could lure rare streaked horned larks away from unprotected lands to safer habitat, she placed three-dimensional lark decoys at a site near Portland. She also set up speakers to waft the larks’ distinctive songs into the air. But one-by-one, the lark decoys started to disappear.

Who could be taking them? The site was securely fenced so Hannah doubted people were sneaking onto the site. While the decoys were designed to be cute and lifelike, she didn’t think that the lark’s natural predators like coyotes and crows would enjoy munching on painted chunks of wood with metal prongs for legs.

So Hannah launched a two-pronged plan to thwart the cunning thief. First, she arranged for the decoys to be firmly anchored to the ground with buried metal plates. Second, she set up a motion-activated camera to catch the culprit.

And what a catch it was! You may recognize this sharp-beaked creature as America’s symbol. That’s right; it is an adolescent bald eagle. Apparently, the little lark decoys fell victim to these birds of prey. Now that the lark decoys are firmly planted in the ground, they can no longer be The culprit! (Photo: Oregon Metro)kidnapped. And thankfully, the experiment can continue.

The theory behind this innovative experiment is called “conspecific attraction”. It rests on the idea that “the larks will be drawn to the new habitat because they see the lark decoys there and hear their song, and think other larks have already figured out it's a good place to live,” explained Hannah. The experiment is being conducted at sites in both Oregon and Washington through a partnership between CNLM, the Port of Portland, Oregon Metro and Joint Base Lewis-McChord (JBLM).

A real streaked horned lark (photo: Rod Gilbert)A candidate for listing under the federal Endangered Species Act, the streaked horned lark has lost extensive tracts of habitat in recent years. While its breeding range once extended from southern British Columbia through western Washington to southwestern Oregon, today it breeds in only a few isolated locations in Washington and Oregon. Whereas it was historically found in open spaces such as native prairies and mudflats, it is now primarily found in open area landscapes that are dominated by frequent human activity. For example, the larks breed on military training grounds, airports, dredge material deposition islands in the Columbia River and farms in the Willamette Valley. To make matters worse, all of the streaked horned lark’s current breeding grounds are on land unprotected for conservation purposes. That lack of protection provided the impetus for the experiment to determine whether the larks could be attracted to safer nearby sites using decoys and song playbacks.

So far, one female lark has been spotted in an experiment plot at Joint Base Lewis-McChord. The experiment will continue through next year. Hopefully from now on, the only species attracted to the decoys will be other streaked horned larks!