Science for a Blue Planet

Featuring cutting-edge work, discoveries, and challenges of our scientists, our partners, and the larger conservation science community.

Marin County Spotted Owls

Science, Good Management, and Good Neighbors = Healthy Owl Population

Adult Northern Spotted Owl, photo Ryan DiGaudio, Point Blue
Adult Northern Spotted Owl, photo Ryan DiGaudio, Point Blue

There’s a burning feeling you get in your neck when craning to view a bird through binoculars, high in a tree in a dark forest.  It’s a feeling that birders, researchers, and nature enthusiasts know well.  Today after too many weeks of desk time I savored that burning feeling.  I was out in the forest, with our Spotted Owl biologist Renée Cormier, her field tech Jenna Dodge, and NBC Bay Area news reporter, Joe Rosato Jr.

What were we doing?  Checking up on a recently fledged Northern Spotted Owl nest as part of the ongoing monitoring of this federally threatened subspecies, found in mature coniferous forests in Marin County, the southern part of the species range.

The Northern Spotted Owl, Strix occidentalis caurina, exists from Southern British Columbia all the way to Marin County, and is listed as a threatened species under the endangered species act.  It is known to many as the poster child for environmental conflict in the Pacific Northwest, where it relies on old growth forests to nest, feed, and raise its young.

In Marin, the owls occur in a mix of forests, including Douglas fir, redwood, bishop pine, and even hardwoods like California bay laurel and oaks.  In contrast to the Pacific Northwest, Marin County has the highest recorded density of Northern Spotted Owls in its range.  In fact, it’s a bird whose range-wide population is declining by 2.9% a year, but here in Marin County, the population is currently stable.

As part of our work to monitor and evaluate birds as indicators of ecosystem health, we have been monitoring Northern Spotted Owls since 1997, in forests managed by the Marin County Open Space District and Marin Municipal Water District and adjacent properties; we also work in collaboration with the National Park Service, who conduct surveys on their lands too.  Our study goals are to track and evaluate the population’s health and provide feedback to the land management agencies on how to help owls thrive in Marin forests.

Finding the nesting locations is important.  Once found we share their locations with the Water District and Open Space District so they can avoid disturbing nesting owls.  Here’s an example: a culvert along a trail may need to be replaced, but if it’s within ¼ of a mile of a Spotted Owl nest, they will delay the noisy repair work until well after the owls have fledged.  The sensitive nesting time for owls in Marin County is from February through July.

Are Marin’s owls at risk?
Luckily for Marin’s owls, there is no commercial tree harvesting, but the owls do face other challenges including urban development, human disturbance from construction, recreation, noise, rodenticide poisoning, and competition from the expanding range of the Barred Owl (a closely related species that competes with the Spotted Owl for space and food).  In Marin, the Barred Owl population is relatively small, but they could continue to increase in numbers, like in other parts of the Spotted Owl range.

Despite these threats, the Marin population is remaining stable.   The ongoing monitoring conducted by Renée and her team will detect early warning signs of decline.

Spending the day in the field with Renée and Jenna was not only a welcome contrast to a typical day for me behind a computer, but it brought me full circle to one of the first times I became aware of, and inspired by, conservation science.  In high school I found myself learning about the challenges faced by Northern Spotted Owls in old growth forests in Oregon and Washington, and debating the conservation need for the species.  I remember digging into scientific literature for the first time in my life.  Who would have thought that 23 years later I’d be spending a day helping to track and report on this sensitive species?

Northern Spotted Owl fledgling. Photo by Kim Kayano, Point Blue
Northern Spotted Owl fledgling. Photo by Kim Kayano, Point Blue

A few fun facts about Northern Spotted Owls:

  • Spotted Owls don’t build their own nests, instead they use abandoned raptor nests, squirrel nests, places where branches and leaves have built up in trees, or nest in cavities.
  • The female owl sits on the nest to keep the eggs warm for a full month, rarely leaving, and being fed by her mate.
  • Most owl chicks leave the nest between 34-36 days of age, but remain close by and are fed by the parents for another month – month and a half, through the end of August.
  • Within 3 days of leaving the nest, the young owls can climb or glide into neighboring trees. Their first flights are awkward and the young sometimes hang upside-down after landing, before either regaining their footing or dropping to a lower perch or the ground.

How You Can Help:

  • If you hike, bike, or walk your dog in the forests of Marin, keep your distance from any owls you find on or near the trail. Avoid spending time near them, as presence of humans can cause changes in their usual behavior.  If they are making noise pitched whistling sound, move on, that means you have frightened them.
  • If you find a young owl along the trail, leave it there, its parents are nearby and will continue to care for it while it’s on the ground. No need to pick it up or take it to a rehabilitation center.
  • If you live near the forests of Marin County, avoid tree trimming, major yard maintenance activities and loud noised during the nesting season, from February through July– owls need quiet to nest.
  • Don’t use rat poisons on your property. Owls can sometimes eat rats that have been poisoned, become sick and die.

Watch the NBC Bay Area news story about this day in the field.