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by Jen Stern

This post is the seventh in a year-long series celebrating the 40th anniversary of the Endangered Species Act. Read the previous post here.

Northern spotted owl

Northern spotted owl (Strix occidentalis caurina). Photo courtesy of National Park Service.

This past year, my grandparents attached an owl box to a tall fence post on their property in rural Petaluma. They were delighted to see two owls using the box this last spring. My grandparents took turns sitting with binoculars and watching in awe as these beautiful creatures tended to their young. One day they invited me over to “owl watch.” It was an amazing experience to see these majestic creatures swoop silently through the air and disappear into a tiny box, only to emerge again and take off with the slightest effort.

The fact that these owls moved right in was a nice surprise, but also a tell-tale sign that owl habitat is limited. The northern spotted owl (Strix occidentalis caurina) lives right here in Marin on the Mt. Tamalpais Watershed. These owls reside high up in the canopy of second-growth conifer and hardwood forests in Marin County. The population of northern spotted owls here is the densest in California—not unlike the population of people in the Bay Area. Thanks to favorable conditions in Marin, the owls here nest just a half- to three-quarters of a mile apart. In the Pacific Northwest, nests are typically one-and-a-half miles apart. With limited space, our owls make do with what they have, living closely and sharing food and shelter.

While the northern spotted owl population is doing well in Marin County, the northern spotted owl is listed as threatened under the Endangered Species Act, with only 560 known pairs remaining in northern California.

So why should we care about these owls? As a top predator, they help to keep the populations of rodents and other animals from growing too large for the resources. If the rodent population were to explode one year, we may see decimated grass populations and a spike in rodent-borne diseases, such as hantavirus. The northern spotted owl not only plays a key role in the food chain, it is also an “indicator species” for forests, meaning scientists study this species to get a larger picture of the health of the ecosystem in which it lives.

While you may not see this elusive owl when you’re out hiking on the watershed, you may hear their call in the evening hours. The call most often heard is a four- or five-note, barking call of whoooo…oowho,oowhooo. Their call is high in pitch and has a short series of notes. If you are lucky enough to see this owl, you can recognize it by its size—the northern spotted owl ranks among the largest in North America. This owl is dark- to chestnut-brown in color and sports round or oval white spots on its head, neck, back and under parts. Its flight feathers are also dark brown and barred with light brown or white.

Northern spotted owl fledgling

Northern spotted owl fledgling. Photo courtesy of National Park Service.

For more information about research results on spotted owls in Marin County, visit www.prbo.org/cms/586. The Point Reyes Bird Observatory has conducted research on spotted owls in Marin County to seek to understand the biology of a secretive species living in close proximity to an urban center, where noise and human traffic can threaten the owl.

I encourage all of you to “owl watch” whenever you have the chance. It is an amazing experience. You may even want to install your own owl box at your home! If you are interested in bird watching in general, there is plenty to enjoy on a hike or picnic by one of the lakes on the Mt. Tamalpais Watershed. You may even see an owl!

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