Wayward wagtail woos flocks of birders to Warm Springs >

What sent a soccer-ball-colored songbird from Asia thousands of miles off-course to Montana?

As local expert birder Caleb Lashway led a morning field trip at Warm Springs WMA near Deer Lodge in mid-September, he spotted a small white and gray bird foraging on a mudflat.

“I don’t think I believed myself for about thirty seconds,” says Lashway, “It looked like a wagtail…but it couldn’t be a wagtail. Montana’s never had one of those before.” But sure enough, it was a white wagtail. Lashway immediately got the word out to the birding community, posting about it on the Montana Rare Bird Alert.

A bit larger and longer-tailed than a sparrow and colored like a gray-and-white soccer ball, these birds are primarily found in Asia and Europe during breeding season before heading south to winter in places like Ethiopia and India. With the exception of a handful of white wagtails that breed 2,300 miles from Montana in far northwestern Alaska, wagtails are almost never seen anywhere else in North America, especially as far inland as Warm Springs.

So how did such a rare bird end up here? The wagtail probably flew south from its breeding grounds in Alaska or Russia, then accidentally flew down the North American coast rather than the eastern Asian coast. Lashway hypothesized that upon reaching coastal British Columbia, a storm could have forced it even farther off course, blowing it west into Montana (several birds more common to the Pacific coast were seen in the area that day as well).

This is a classic example of vagrancy, a well-studied phenomenon where birds are spotted far away from their traditional haunts. A variety of factors can lead to vagrancy, including individual birds making errors in their internal navigational compasses, unusual weather events, and a natural propensity for young birds to disperse in search of mates and a new place to live. Scientists used to think that vagrancy was as simple as a bird making a mistake, but biologists now assert that this phenomenon is important in the greater context of a species. Pioneering individuals can find new suitable habitat, expanding a species’ breeding or wintering ranges which provides security for that species’ survival. A small population of warblers a hundred miles west of their normal range, for example, could act as a safeguard if a disease hits and wipes out the warblers from the rest of its range. Vagrancy is both incredibly complex and still shrouded in mystery.

Does this mean that white wagtails are going to colonize Montana? Probably not. That would require a mating pair, ideally multiple to limit inbreeding. But that didn’t dampen the excitement felt by the 70 or so birders that gathered to see the bird, some driving from as far away as North Dakota.

—Braden Collard, Montana Outdoors

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