A Closer Look at Burrowing Owls cover

A Closer Look at Burrowing Owls

By


You may not know this, but there is an owl that lives underground right in our own backyard—San Diego County.
Colleen Wisinski is a senior research technician for the San Diego Zoo Institute for Conservation Research.


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A Closer Look at Burrowing Owls

The Burrowing Owl

You may not know this, but there is an owl that lives underground right in our own backyard—San Diego County.

Yes, the burrowing owl lives in a ground squirrel burrow near you where it is busily catching mice, insects, and small birds to feed up to a dozen young owlets.

Burrowing owls are super cute, no doubt about it. Check out their great, big forward-facing yellow eyes with broad, white expressive eyebrows. They draw your attention and keep you mesmerized as they dance, swaying and bouncing on long featherless legs at the entrance to their burrow home. Once you know where to look for them, they are easy to spot.

Habitat

Burrowing owls range widely across the western US and make use of a variety of “grassland” habitats, from open prairie to empty suburban lots to airports.

But their populations are declining, mostly due to loss of habitat and eradication of the fossorial (digging) mammals that they depend on to build burrows. One solution is the installation of artificial burrows. However, artificial burrows are not self-sustaining like natural squirrel burrows and, although we know the owls use them, we don’t know how they compare to natural burrows.

Standing Watch

Standing Watch

A male burrowing owl guards his burrow entrance

Squirrels First

We go to great lengths to get our squirrels established.

First, we capture them at sites where landowners don’t want them around. We catch and release groups that are familiar with each other. We move them to above ground-below ground acclimation chambers, where they spend a week at the site before we let them out.

Working with San Diego State University, we weed-whack back all the thick non-native grass. We bring in cover—logs and branches—that squirrels can use to hide under, burrow under, or stand atop to look for predators. We provide sweet, juicy slices of apples and yams for a few months after release. And, we monitor them closely after release, using camera traps, live traps, radiotelemetry (for some) and direct observations. We’re getting squirrels established and burrows dug, so it is a success, but we would like to increase our success.

Breeding Season

At this point, the breeding season is in full swing. We are monitoring almost 30 nest burrows (both natural and artificial);

this includes placing camera traps at about 20 of the burrows. We check on each burrow about once a week (we don’t want to visit too often and risk disturbing the birds) and do any camera trap maintenance needed, such as changing batteries and switching out the memory cards that contain our priceless data in the form of photographs. We also watch the birds from a distance to figure out what stage of the breeding season they are in—for me, this is the best part!

I See You!

I See You!

A camera trap photo shows a burrowing owl pair allopreening at their burrow entrance.

Observations

Over the last two months, we have been inventorying burrows and following their progression through the breeding season.

On any given day, we head out to the field in the morning and work our way through our route for the day checking on each burrow as we go. When we arrive at a burrow, we observe from the truck (which acts as our blind) from a safe distance to see what is going on at the burrow. Early in the breeding season, we might see both parent birds or just the male standing guard at a burrow. In general, the males are lighter in color than the females, because they spend more time outside so the sun bleaches their feathers. As the breeding season progresses, the difference in plumage becomes more marked, as the males get more and more bleached. By the end of the summer, though, it can be hard to tell the males and females apart as both get bleached by the sun.

His & Hers

His & Hers

Note the difference in coloration (female on left, male on right) with this burrowing owl pair.

Watching out

Once the pair has chosen their nest burrow, we usually only see the male of the pair;

he is often standing watch over the burrow from nearby (often at the entrance of a satellite burrow where he spends much of his time—we call it the “man cave”). At this point, the female is spending most of her time in the burrow incubating the eggs. After about a month, the eggs hatch, and two weeks after that, the young start to come out to the burrow entrance. We usually do a quick examination of the photos in the field to help us determine if there are chicks present, but we also get good clues from the female’s behavior. If she is very protective of the burrow or stays very close to the burrow when we approach, it’s a safe bet that there are babies in the burrow.

Two Burrowing Owl Chicks

Two Burrowing Owl Chicks

Two burrowing owl chicks rest at the burrow entrance while Mom stands guard. Camera trap photo.

Next Steps

Currently, we have nests in all different stages of breeding—some have pretty large chicks, some still have eggs, and some still seem to be deciding if they are even going to breed.

In the coming weeks, we will band all of the owls from burrows that have camera traps, and over the next several months, we will pour over the hundreds of thousands of camera trap photos to catalogue how often prey was delivered to the burrow, what type of prey was brought, what types of predators come to the burrow, and other pertinent information. This is a huge undertaking, since we have almost 40 camera traps set up that can take over 30,000 pictures in one week alone! Any volunteers? Seriously, if you’re interested in helping, visit our volunteer page and sign up! Who wouldn’t want to spend their time looking at pictures of these adorable and comical little birds?!

http://zoo.sandiegozoo.org/content/volunteer

Burrowing Owl Sequence

This is a time-lapse video... Owls don't move this fast!

Video