‘Bird detective’ explains martins’ behavior

I met Bridget Stutchbury in the early 1980s at the University of Oklahoma Biological Station. I was teaching ornithology, and she was a visiting graduate student from Yale looking for a place to study the social behavior of purple martins. We had dozens of pairs of martins in six apartment houses on campus, so it was a perfect fit.

Fast forward to 2010. I received a copy of “The Private Lives of Birds: A Scientist Reveals the Intricacies of Avian Social Life” by Bridget Stutchbury ($25, Walker & Co.) in the mail. And sure enough, purple martins feature prominently among the species covered.

The book is a fascinating read, and I recommend it to anyone interested in bird behavior and life as a field ornithologist. In a recent phone interview, Stutchbury shared with me some insights that led to the book.

In the introduction, she describes herself as a “bird detective,” so I asked why.

“Two reasons,” she explained. “First, I‘ve spent more than 20 years stalking my subjects. I creep through the woods to find birds, and I spend long hours studying them on stakeout.”

“Second, I use technology just like on CSI. I use high-tech tracking devices, take blood samples and do DNA testing.”

“Observations plus fancy tools make a bird detective.”

Next I asked Stutchbury to explain some of the findings she’s discovered over the years.

“I’m interested in migration and recently began using tiny tracking devices called geo-locaters to follow purple martins and wood thrushes to their winter grounds. The difficulty is that the birds must be recaptured to download the data from the geo- locators. Last year we recovered 11 wood thrushes and 20 purple martins.

“I was struck by the similarities in migration between these two unrelated birds, a swallow and a forest-dwelling songbird. Both race to Mexico upon leaving the U.S., then stop there for several weeks before moving on to their final destinations in South and Central America. At this point, I don’t know why they take such a long break during fall migration.”

Then I noted that the book deals a lot with human behaviors such as cheating and divorce. Among songbirds, I asked?

“Yes, humans have always admired songbirds because they appeared to be completely monogamous. But by capturing birds, taking blood samples and testing their DNA, we now know that many songbirds routinely cheat on their mates. It turns out about 40 percent of young songbirds are sired by neighboring males. It’s a real numerical advantage for males. They can produce far more offspring by mating with several females than if they stayed true to their mates. And females get to pick from a variety of males in addition to her mate. She chooses those that sing best and/or flaunt the brightest colors.”

So is this what leads to divorce among songbirds? I asked.

“In part, yes. From year to year, 70 to 80 percent of songbirds acquire new mates. But even during the same nesting season, breakups occur. My husband and I have studied blue-headed vireos, and we’ve discovered that females look for a new mate as soon as her first brood leaves the nest. This enables females to rapidly re-nest and get in a second brood. The males raise the fledglings for the next three weeks. By the time the young are independent, it’s too late in the summer for males to acquire another mate. This system enables females to double their reproductive rate.”

Finally, I asked if her work with purple martins had any practical implications for people trying to attract martins to an apartment house.

“Female martins usually return to the same colony year after year. This ensures that their will be plenty of males to choose from. That’s why it’s so difficult to get martins to establish a new colony. My husband and I have been trying for 20 years. Two professional ornithologists, and we can’t even get martins to use our housing.”

If you’d like to learn more about “The Private Lives of Birds,” read the book.

Send questions and comments to Dr. Scott Shalaway, RD 5, Cameron, WV 26033 or by e-mail via my Web site, http://scottshalaway.googlepages.com.

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