What are burrowing owls?
Meet "The Burrowing Owls"
"Athene cunicularia" in Latin ·🦉· "Little Miners" by nickname
Recently (Spring 2021), I did a presentation for the Girl Scouts where I taught them about the burrowing owls by teaching them this song:
However, keep scrolling for even more information about the burrowing owls and their predicament.
Who live in California
17 subspecies in the world ·🦉· 2 subspecies in the US
Burrowing owls are found in North and South America.
The 2 subspecies in the US are the Western burrowing owl (A. cunicularia hypugaea), which can also be found in Canada through Central America, and the Florida burrowing owl (A. cunicularia floridana), which can also be found in the Bahamas. All burrowing owls are very similar in appearance and behavior.
The owls are migratory in much of their range, but in temperate areas some are resident and some are migrant, making California an especially important winter habitat for the birds.
They're "Hand-Sized" Owls
Height: 7.5-9.5 inches ·🦉· Weight: 5-6 Ounces ·🦉· Wing span ~22 inches
Different from Other Owls
No "ear tufts" ·🦉· Long legs to run with ·🦉· Coos instead of hoots ·🦉· Active during the day and night
they live in the ground!
🦉· The only owl to live underground ·🦉
While they can dig their own burrows, they're often found in the burrows of ground squirrels, especially in California. While they'll still prep their own burrows to live in, they leave it up to the ground squirrels to clean them out after they move on.
To excavate burrows, owls face into the burrow and scratch backwards with their feet. Owls also walk through the burrow tunnel with out-stretched wings, dislodging dirt from the walls. In California and New Mexico, it's been reported that the owls will even use their bills to excavate.
After excavation, owls bring lining materials to their burrow's entrance. This material consists of dry horse, cow, and dog poop. 💩 Once an adequate pile of material is accumulated, the owls shred the material and carry it into the burrows. They line the nest chamber floor as well as the tunnel and entrance. The lining provides insulation and serves to camouflage the owls' scent, and its meal's, from predators. The poop can also serve to lure their prey, like beetles, into their burrow for a meal delivered.
Each pair uses multiple burrows, called their primary and satellite burrows.
Natural burrow
Artificial burrow
Burrow mounds
In Open Grasslands
Prairies ·🦉· Agricultural Lands ·🦉· Bases ·🦉· Golf Courses ·🦉· Open Fields
The owls reside at lower elevations in much of California, often below 200 ft. They choose open areas, typically with few trees where predators could lurk, with short grass (< 6") around their burrows and structural heterogeneity elsewhere: long grasses, shrubs, rock, and brush piles. They're often found living among ground squirrels, and will rely on the warning calls they make as additional security.
How do they Sound?
🦉· Remember: they coo instead of hoot! ·🦉
The male burrowing owl dips his body forward as he sings, "cu-coo, cu-coo." This song, begun at sunset and repeated every hour at night during courtship, is also emitted for territorial defense.
Females rasp when begging for or receiving food from the male during incubation, or when passing food to the young.
Juveniles utter a buzzing “rattle” resembling the sound of a rattlesnake when disturbed, or when cornered by predators.
All owls know the "chatter" alarm call and use it to warn each other.
Males
Mating and Territorial "Coo"
Females and Juveniles
Food "Rasp"
Juveniles
Rattlesnake "Hiss"
All Owls
Defensive and Warning "Chatter"
Males and Females Are Different
🦉· But play equally important roles ·🦉
When coupling up in the Spring, males will provide food for and perform a "bobbing" and "coo-cooing" to woo their mate. Females decide when their mate's wooing is adequate enough to copulate through "rasping."
Males tend to be slightly larger with lighter feathers, bleached by the sun, because, during the summer, it's his role to guard the burrow entrance while the female incubates their eggs inside.
However, once the demand for food from their chicks grows, both will hunt for food to bring home.
In the photo on the right, the male is on the left and female is on the right.
They Can Have Lots of babies!
2-12 eggs per clutch ·🦉· 1 clutch per year
Burrowing owls become sexually mature at 1 year. They usually live ~3-5 years, but can live up to 9 (here's an owl that lived until 9 in captivity). They pair up starting in February, stay monogamous throughout the breeding season, and their chicks emerge in May after staying below ground for several weeks. The chicks will stay with their parents all summer, learning the skills they'll need to survive on their own. By September, juveniles molt and disperse to seek their own burrows. Their parents typically migrate or move to other local burrows for the winter.
What They do
🦉· They chill ·🦉
Burrowing owls spend most of their day hanging out by their burrow's entrance or on nearby short perches or mounds. The activities they can be found doing include:
Sunbathing (top right photo)
Stretching (bottom right photo)
Eating
Preening
Preening each other
Molting
Roosting
Dust-bathing
Running
Rousing
Coo-cooing
Feeding their chicks
Teaching their chicks
Wrestling
Keeping watch for, hiding from, and defending against predators
Bowling prairie dogs
Domineering
Hunting
Visualizing
Playing with toys
The video below covers what it's like for a brood of owls to grow up over the summer. 😍
What they eat
Mostly insects and small rodents ·🦉· But also amphibians, reptiles, crustaceans, and birds
Of the insects, in Santa Clara County, California burrowing owls mostly eat earwigs (which can be found in the microclimate inside their burrows), beetles, and grasshoppers. In dwindling populations, finding prey with the highest biomass in their diet is the most important for their survival. These are the California vole (avg. mass = 53 grams) and Botta's pocket gophers (avg. mass = 155 grams), which both do well in urban settings. Because the owl can only carry one prey back to the nest at a time, the bigger the better.
Burrowing owls take horse, cow, and dog poop 💩 into their burrows to lure prey, especially beetles, into their homes.
They need enough foraging habitat in the landscape they live in order to succeed long-term as a species, making "urbanization of grasslands and agricultural lands" the #1 threat to their survival.
A parent owl brings back a small rodent for their chicks to rip into shreds and consume.
What Eats Them
🦉· Everything that can ·🦉
What's Happening to Them
🦉· Their populations are declining rapidly everywhere ·🦉
Endangered in Canada
Threatened in Mexico
Bird of Conservation Concern in US
Endangered in Minnesota
Threatened in Colorado [source, source]
Species of Special Concern in California, Montana, Oklahoma, Oregon, Utah, Washington, and Wyoming
In California, 60% of breeding groups found in the 1980s disappeared by the 1990s.
Between 1988 and 2002, 66% of locations lost.
Only >50 owls remain in all of Santa Clara County, California.
Burrowing Owl Billows is at the Shoreline location.
Why is this happening to them
🦉· Because of us 😅 ·🦉
#1 Threat: Urbanization of grasslands and agricultural lands
Urban sites are subject to disturbance, habitat loss, and poor habitat conditions. Less habitat means fewer places for the owls to live and less to eat where they can live.
Urbanization involves:
Development
Auto strikes
Exterminating rodents
Secondary poisoning
More mesopredators (badgers, foxes, skunks, etc.) & corvids (crows)
Weed abatement & Tall grass
Recreationists, Dogs & Cats
Surface and Soil disturbance
Google and Microsoft are both developing next to Shoreline Park, where Burrowing Owl Billows is.
Google's cats have been a big problem, but they're working with the city to create a plan to eventually remove the feeding stations near the burrowing owl nesting sites.
Land developers are often uneducated or don't care and will destroy owl-habitat in order to profit.
#2 Threat: Agricultural Practices
Conversion to vineyards
Lining irrigation ditches
Discing to eliminate weeds
Exterminating rodents
Secondary poisoning
#4 Threat: Climate Change
By 2080, these owls could lose 77% of their current breeding range to fires intensified by climate change, which will disrupt their winter range as well, leaving only 33% intact.
By 2100, there'll be a >70% increase in grasslands, replacing shrub and mixed evergreen woodland.
This could actually be better for the burrowing owls in the long run, but will the fires change their habitat too often in the interim? What about the intersection of human activities, population growth, and the other effects of climate change?
What we're doing to save them
Relocation ·🦉· Government Regulation ·🦉· Habitat Enhancement ·🦉· Education & Protection
Relocation
Relocation has proved to have a very low success rate for the owls, so it should only be done when absolutely necessary. Multiple studies have been conducted by conservationists over the years, and all results aren't ideal. For more details of the success rate of their projects, see slide 83 of this deck.
Government Regulation
There are multiple federal and state rules such as the federal Migratory Bird Treaty Act and the state California Fish and Wildlife Code (Section 3503.5) that prohibit the taking, possession, or destruction of any burrowing owl, bird or body parts, young or adults, nests, eggs, or products. There are also state regulations requiring developers to survey land (see photo on right) for burrowing owls before development. For a full list of all the federal and state regulations that help protect and assist the burrowing owl, see slide 67 of this deck.
Habitat Enhancement
Conservationists can increase owl populations by enhancing the habitat of existing burrowing owl nesting sites or by attracting the owls to new ones. The owls can do well in developed, urban, and agricultural areas if nests are protected from disturbance and there is enough foraging habitat.
Principles for successful habitat enhancement:
Develop a long-term plan that sets aside adequate areas for burrowing owl protection and management; exclude disturbance activities.
Enhance sites for nesting with artificial burrows. (See photo on right)
Enhance the site for ground squirrels by bringing in mounds of dirt (don't use good soil!) and encourage healthy ground squirrel populations.
Keep grass short (<6 inches) around nesting burrows and remove trees.
Enhance foraging opportunities by creating a structurally heterogeneous prey habitat; no pesticides or poisons. This is what we're doing by planting California Native plants at Burrowing Owl Billows in Shoreline Park❗️
See slide 72 of this deck for more about habitat enhancement.
Education & Protection
Throughout Shoreline Park you will see the signs featured in the photos on the right. These signs help to remind the public not to cross the fence into the open space where the owls reside, but recreationists (sometimes with their dogs, even though dogs aren't even allowed in the park) have still been spotted on hidden cameras doing just that.
If a burrowing owl's nest is disturbed, it can abandon it, even if eggs or chicks are present.
Conservationists are now looking into building a larger fence around Burrowing Owl Billows in Shoreline Park, as the current fence has been repeatedly trespassed and the signs ignored.
Please report any trespassing by
📞 calling 650-930-6655
and · or
✉️ emailing aishawithaneye@gmail.com
