Thursday p.m.: When Burrowing Owls Misbehave
By Hugh Powell
August 8, 2008
5:00 p.m. Sometimes, conservation stops being a balancing act and becomes one of those circus routines where a juggler tries to keep a roomful of plates spinning on poles. Victoria Garcia, of the University of Arizona, knows just how that feels.
Garcia studies Burrowing Owls on Naval Base Coronado, an assortment of docks, lawns, runways, and military buildings wedged between San Diego and the Pacific Ocean. Owls have never been numerous there, but in the last 20 years numbers have dropped by 90 percent, prompting managers to look for emergency measures. There are just a few catches:
- The owls nest in the burrows of ground squirrels that are also disappearing, in part due to the efforts of groundskeepers at the base golf course.
- Some Burrowing Owls develop a taste for baby Least Terns, which they pluck from their nests atop military buildings.
- The California Least Tern is an endangered species, with only about 1,700 individuals remaining and their own team of conservation scientists committed to their survival.
- Certain problem owls have been discovered with stockpiles of up to 20 tern chicks stashed away in their burrows. (Apparently, most owls are content to eat other prey, but once one discovers terns, it becomes a repeat offender.)
- In an effort to save the Least Terns, officials have no choice but to relocate – or shoot – problem owls.
- As if the situation isn’t complicated enough already, endangered snowy plovers roam Coronado’s beaches, demanding their own share of consideration. And military jets that use the runways pose a constant hazard to all three species (and vice versa).
So Garcia was asked to devise a way to increase owl numbers – without jeopardizing any other species. “It’s like trying to conserve a fox in a henhouse,” she said. But she broke down the situation into its constituent parts and came up with a plan.
She looked for ways to safeguard owl nest sites: ease up on the ground squirrel control measures, or construct artificial burrows that won’t collapse in sandy soil near the beach. Next, she suggested ways to make it easier to catch prey other than terns: keep the grass on base lawns shorter through more frequent mowing.
And if these pro-owl measures should lead to a resurgence in problem owls? Garcia advocates a firm but gentle hand: Supply the troublemakers with extra food while Least Tern have chicks in the nest. And if that doesn’t work, put a cage over the burrow to make sure the owls don’t leave.
It’s too early to know how the recommendations will work – they’re still too new. But Coronado’s problems are likely to be repeated elsewhere, Garcia says. As urban areas grow and green spaces shrink, conservation scientists will be faced with smaller and smaller rooms – and more and more plates to keep spinning.
P.S.: three science papers in three sentences: (1) Two 1,500-year-old eggs discovered at a Oaxaca, Mexico, archeological dig belong to a Hermit Thrush and a Sora, despite being nearly 1,000 miles south of either species’ current breeding range. (2) Eastern Bluebird nestlings raised at golf courses somehow remain pesticide-free, despite gorging on insects during the prime spraying season. (3) Judging from its DNA, the enigmatic Black-backed Woodpecker seems able to hopscotch its way from one forest fire to another, from Idaho to Quebec, without showing any sign of evolutionary isolation.
And one more thing: Did you know Burmese pythons are eating Wood Storks and frigatebirds in the Everglades? Read the full story over on the Smithsonian website.