Eyes and Ears on Burrowing Owls: A Project of Pomona Valley Audubon Society

Southern California has fourteen Audubon Chapters, each with their own membership areas, interests and activities. Pomona Valley Audubon Society (PVAS) is located about fifty miles east of Santa Monica and we don’t bump into each other very often. When I ran across their newsletter report on this Burrowing Owl project, I was very impressed and wanted to share it with our SMBAS members and readership, in the hope that it might spark similar projects elsewhere. Suzanne Thompson kindly supplied the photos and the following report, which is also on their blog. A small group can accomplish a lot when they put their minds to it. [Chuck Almdale, Ed.]

Burrowing Owls are small owls that use underground burrows for nest sites and shelter.  These appealing birds have bullet-shaped bodies and long legs, giving the appearance of an owl popsicle, and engage in amusing antics such as turning their heads almost upside down to get a good look at birders who are trying to look at them.  They are often out in daylight and thus are easier to observe than the rest of the owl clan.

1. Burrowing Owls

At one time these owls were very common in California and, even as recently as 10 years ago, they were a common sight in the Chino and Ontario areas of the Pomona Valley.  However, loss of habitat, the use of pesticides, and the killing of burrow-excavating ground squirrels have drastically reduced their numbers.

2. Eyes and Ears

Our Eyes and Ears on Burrowing Owls Project focuses on four areas in Chino and Ontario where there are still active nesting grounds for the owls: The goal is to maintain a healthy, viable breeding population of Burrowing Owls in the PVAS area.  Each of the four nesting sites is critical because it currently supports or has the potential to support a significant number of active burrows.  The areas are close enough for owls to travel between them, thereby promoting genetic diversity.

3. The Preserve Sign

A major focus has been the Burrowing Owl Preserve in Chino, a 24-acre site that was established about ten years ago to mitigate for the loss of owl habitat due to development.  Owls nested in the artificial burrows initially but eventually the artificial burrows fell into disrepair and were no longer used.  PVAS has established a collaborative relationship with the homeowners’ association that is responsible for the preserve.

4. Los Osos High School group

The restoration plan included the installation of eight new artificial burrows, weeding to remove invasive weeds, and the sowing of California native wildflower seeds.  The work started in the fall of 2019 when high school students built the wooden burrow boxes in their shop class using the San Diego Zoo Research Institute plans for an improved burrow.  PVAS members, along with college and high school students, got together for several weeding parties at the preserve to remove extensive stands of tumbleweed and other weeds.  Replacing invasive weeds with native plants should attract more insects and lizards, thereby improving forage for the owls.

5. Finishing the boxes

6. Weeding the Slope

Over 55 volunteers attended the two burrow installation days in late January.  Some volunteers completed the burrows, securing buckets to the lids so the burrows could be accessed for cleaning or banding, and adding hardware cloth, legs, and tubing.  Others worked on weeding or removing brush.

7. A fully assembled nesting box and tube tunnels

A fully assembled box has two entrances and nineteen feet of tubing.  The first three feet of tubing at the entrance is larger in diameter to create an “anti-predator patio.”  This allows one or more owls to quickly run into the burrow if a predator appears.  The narrower tubing closer to the box should stop predators from continuing down the tube and into the nest.

8. A mini-excavator from Southern California Edison

9A. Digging the trench and laying the tubing

9B. Filling the trench, nest entrance below

Southern California Edison volunteers brought and operated a mini-excavator to dig most of the trenches.  The excavator crew finished their work by early afternoon and teams of volunteers began covering the boxes and tubing with poultry netting and hand filling the trenches.

10. Digging by hand #1

11. Digging by hand #2

The mini-excavator could not handle the very steep slope at the last installation site, so a crew of 10 volunteers hand dug those trenches in hard, compacted soil.  After a day and half of hard work with shovels and pickaxes, the hand-dug trenches were finished, and the burrows and tubing were installed.

12. Burrow entrance

When the burrows are installed, all that shows above ground are the burrow entrances, two for each burrow.

13. Seeding

In February, we waited anxiously for rain so the native plant seeds could be sowed.  Finally, in early March, when some substantial rain was forecast, the seeds were spread and lightly worked into the ground.

14. Future Tenants

The future holds more weeding and seeding, the installation of low perches for the owls, and, we hope, Burrowing Owls moving into their new digs.

Above Text: Suzanne Thompson
Photo Credits:  Carol Coy, Kim Dillbeck, Sherry Schmidt, Suzanne Thompson
Information contact: Suzanne Thompson, Chair, PVAS Eyes and Ears on Burrowing Owls