Thursday p.m.: When Burrowing Owls Misbehave

By Hugh Powell
August 8, 2008
Burrowing Owl Burrowing Owl by Mongo via Wikipedia.
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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:

  1. 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.
  2. Some Burrowing Owls develop a taste for baby Least Terns, which they pluck from their nests atop military buildings.
  3. 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.
  4. 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.)
  5. In an effort to save the Least Terns, officials have no choice but to relocate – or shoot – problem owls.
  6. 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.


  • I remember very well from my years working in the Everglades National Park a famous pair of Burrowing Owls that nested in a pile of PVC pipe on the helicopter ramp at the Homestead Municipal Airport. The owls just stuffed grass and straw into the end of the pipe and proceeded to raise three chicks. I concluded (perhaps rashly) that providing nest sites for Burrowing Owls was no big challenge, but I bow to no man in my respect for the Navy’s ability to screw things up.

    The Veteran Naturalist

    (Clarification: the Veteran Naturalist is a 20-year veteran of the Air Force; you can regard his jab at the Navy as good-spirited military rivalry)

  • Laura Erickson

    I am in awe of your ability to synthesize these fascinating papers into interesting, brief blog entries, Hugh!

  • “And military jets that use the runways pose a constant hazard to all three species (and vice versa).”

    Also good to mention that without the military jets, it’s unlikely any of the three species would be there.

    The whole situation reminds me of another military base on San Clemente Island, where “endangered” San Clemente Loggerhead Shrikes ( nest surrounded by the “threatened” SCI Foxes (, and the joint efforts to increase populations of each without it negatively affecting the shrikes.

    Intriguing one-sentence summaries from the other talks; any chance that we’ll find out more?

  • Anne Hobbs

    As I read those three scientific papers in three sentences, all I wanted was more information. I sure hope you’re going to give us more!

    Thanks so much for the Burrowing Owl information. As an example of why there are seldom easy answers to bird “situations”, it takes the cake.

  • msc

    Sitta, why wouldn’t the three species be there without the military jets? Is it because without the base, the whole place would be paved with McMansions?

  • Thank you so much for posting brief mentions of some of the most interesting papers at the AOU conference. I’ve always wanted to attend a conference so this is a welcome glimpse.

  • Burrowing Owls are one of my favorite birds yet to see (FBYTS) – It just goes to show how important large-scale conservation is because without huge protected areas, we will have to over-manage and choose one species over another… then we are basically left with a zoo.

    Fascinating information from the AOU conference. Wish I was there!!

  • @msc-

    That’s what I was getting at: if you look at the rest of San Diego County, you’d be hard pressed to find big chunks of land like Coronado where Burrowing Owls could live because of development. Not necessarily McMansions, either, but development of all sorts. Some kinds of development, like airports, don’t seem to bother BUOWs; in fact, next time you land at San Jose Airport in CA, keep an eye out the window of your plane–there’s actually a large breeding population of BUOWs on airport grounds, actively managed to increase population numbers and minimize conflicts with aircraft. Someone even gave a talk about it at the Lab a year or two ago (

Thursday p.m.: When Burrowing Owls Misbehave