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Saving the Burrowing Owls

Saving the Burrowing Owls

Burrowing Owl being held while one hand slightly extends owl's wing

Burrowing Owl in hand

A dwindling population of a tiny owl in Southern California has a chance at a comeback, thanks to a collaborative effort by scientists from CDFW, the San Diego Zoo’s Institute for Conservation Research (ICR), Caltrans and the U.S. Fish and Wildlife Service.

The Western burrowing owl (Athene cunicularia hypugaea) is currently listed as a Species of Special Concern, and nongame scientists have long been concerned about their viability and survival. Breeding populations have especially declined in the central and southern coastal areas, due in large part to a combination of habitat loss and eradication of the ground squirrels that dig out the burrows where the owls make their nests. In San Diego County specifically, the once-widespread population has been reduced to a single breeding node in the Otay Mesa region, just north of the Mexico border.

Two groups in particular have been monitoring these owls carefully, in an effort to help. Biologists from Zoo’s ICR have spent seven years assessing owl population status and productivity, including assessing the feasibility and effectiveness of artificial burrows, refining techniques to help the ground squirrels thrive and disperse into new areas and developing a system of identifying potential new locations where the owls might thrive. Much of ICR’s owl research has been conducted at Brown Field, a small municipal airport near the border within the City of San Diego, and on an adjacent property owned by Caltrans.

Meanwhile, about 10 miles from the Brown Field study site, CDFW scientists have spent a decade working to create more suitable burrowing owl habitat at Rancho Jamul Ecological Reserve (RJER). Efforts there included installation of artificial burrows and mowing the tall grass to foster a low-growing grassland suitable for burrowing owls and ground squirrels. Despite their best efforts, CDFW scientists studying the Rancho Jamul site have experienced many years of disappointment -- although wintering owls have shown up every year, none have stayed and attempted to breed on the property. But conditions have been improving over the last four years, thanks to the implementation of a grazing program that reduced dense thatches of old grasses and expanded areas of open ground. As habitat changed at Rancho Jamul, CDFW scientists observed more squirrel burrows, and the conditions seemed just about right for the owls.

This spring, an approved development project at Brown Field began to take shape – and it became evident that the timing for an owl translocation project was ripe at last. Thanks to efforts by Caltrans, which incorporated burrowing owl habitat restoration as part of their mitigation effort for a nearby highway, CDFW staff believed the owl population to be strong enough to support a translocation effort. Also the spring season, just prior to egg-laying, is likely the optimum time to move the animals. After looking at many options, scientists decided to try to move five pairs of breeding owls to RJER in the hopes that they would establish a new population and thrive.

The full conservation team – which included CDFW, the U.S. Fish and Wildlife Service, the City of San Diego, Metro Air Park, Schaefer Ecological Solutions and the San Diego Zoo – was on board and ready to move the owls. In March 2018, the team caught five pairs and moved them to hacking cages at RJER. The owls lived in the cages for about one month to give them time to acclimate to their new surroundings. By the time the cages were removed, each female had laid at least one egg in the artificial burrow chamber.

CDFW Environmental Scientist Dave Mayer has worked on this project for years and is anxious to see efforts at RJER finally pay off. The presence of the eggs, he said, was thrilling to see. “More owls, and at diverse locations, is what it will take to conserve this species in San Diego County. This first step was a long time coming, but I have all my fingers crossed that it’s going to work.”

This successful multi-agency partnership will continue long past the actual translocation day. Scientists banded the owls and fitted some with radio transmitters. ICR staff will monitor the owls themselves, while CDFW staff will monitor the grassland and the grazing program, and perform inspections and repairs of the artificial burrows twice a year. After five years, CDFW will perform regular monitoring of the owls, the habitat and associated grazing practices, and the general status of the ground squirrel population.

Mayer is proud of the work achieved so far in this unusual project. “We built a better mousetrap, with the Zoo’s help,” he says. 

General information about California’s bird species of special concern can be found on the CDFW website, along with the link opens in new windowspecies account (PDF) for the burrowing owl and information about Rancho Jamul Ecological Reserve.

The San Diego Zoo has also issued a link opens in new windownews release with more details about the burrowing owl translocation project.

All photos © San Diego Zoo Global, all rights reserved

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For 21 Years, Volunteer Has Kept Tabs on Morro Bay’s Black Brant

For 21 Years, Volunteer Has Kept Tabs on Morro Bay’s Black Brant

A black brant, similar to a dark-colored goose, feeds on eelgrass in a sandy bay shoreline.
Banded black brant feeding on eelgrass

A man with a gray beard and glasses, wearing a baseball cap and dark gray jacket, stands next to a spotting scope on a tripod, near Morro Bay, with Morro Rock in the background.
Volunteer John Roser in the field at Morro Bay

Hundreds of dark-colored birds fly together in a bright blue sky
Flock of black brant in flight above Morro Bay

A goose-like seabird with a black beak, dark hood, neck and coat, and white underside floats on bay water
Black brant in Morro Bay

John Roser began hearing the stories shortly after he moved to Los Osos, San Luis Obispo County, on the shores of Morro Bay in the mid-1990s.

Longtime birders, waterfowl hunters, biologists and other coastal residents were all saying the same thing: It seemed fewer black brant were showing up on the bay each winter.

The coastal sea goose is a cultural icon of the area, the signature species of the Morro Bay Winter Bird Festival and a temporary visitor welcomed by locals as the geese arrive each fall from their summer breeding grounds in the Arctic. When the geese are present in big numbers, you can hear their cacophony almost anywhere on the bay from November through April or until the warm environs of Baja California lure the birds farther south on their migration.

Roser, who holds a degree in biology from Cal Poly San Luis Obispo and spent 25 years as an environmental educator, set out to see if the old-timers’ stories were true. For the past 21 years, he has provided CDFW and brant biologists throughout the Pacific Flyway with their most credible and reliable source of data on wintering brant in Morro Bay.<

“I’m retired, and I wanted to take on a volunteer project that would make a difference in this community,” Roser said of his motivation. “I wanted to create a Morro Bay specific data set significant enough that it would be valuable in brant studies and research across the Pacific Flyway.”

Roser’s initial efforts in 1997 focused on reading and reporting bands on individual birds with the help of a high-powered telescope. He has recorded more than 4,000 bands, including one affixed by a Russian ornithologist to a bird in Siberia some 5,000 miles away from Morro Bay where Roser spotted it. In addition to counting individual birds, Roser developed a formula – in consultation with brant biologists – to calculate the number of “brant use days” in Morro Bay each winter.

Roser’s retirement project has led him on a brant-like odyssey.

He banded brant one summer in Alaska, worked in Humboldt Bay with leading brant researcher Jeff Black and his Humboldt State University graduate students, and traveled to Baja California to help biologists read bands on birds at the extreme end of their southern range. Much of Roser’s winter observations take place at CDFW’s Morro Bay Wildlife Area.

“John is our go-to guy on the ground in Morro Bay for sure,” said Melanie Weaver, the head of CDFW’s Waterfowl Program. “We only have two employees in our program, myself included, so we depend on regional staff and volunteers like John to help compile survey data. John is part of the local community, he cares, and he is close to the resource.”

The data Roser supplies are incorporated into CDFW’s Mid-winter Waterfowl Survey, which is used to set hunting regulations for the following waterfowl season.

What attracts brant to Morro Bay is the same thing that prompts the birds to stop at other coastal bays along their southward migration: eelgrass. The underwater seagrass grows in shallow marine environments and is the birds’ primary food source.

Roser’s initial research in 1997 confirmed the reports he was hearing: The wintering brant population in Morro Bay had declined significantly and corresponded with a crash in eelgrass acreage in the bay.

While CDFW surveys from the 1930s through 1960s documented Morro Bay’s wintering brant population as high as 11,800 birds, Roser’s first survey in 1997 recorded a population high of fewer than 700 birds.

The eelgrass crash in the mid-1990s was temporary and well-understood, caused by an influx of sediment from a fire-ravaged landscape, a deluge of freshwater from a rainy year and warming El Nino ocean conditions. As environmental conditions normalized in subsequent years, the eelgrass rebounded, and the brant returned. Roser counted a population high of 4,600 birds in Morro Bay in 2001.

The story since then, as told in Roser’s annual reports to CDFW, is of another dramatic crash in eelgrass acreage in Morro Bay and a corresponding drop in the numbers of brant wintering there. Unlike the eelgrass crash of the mid-1990s, the latest decline has been more persistent and perplexing.

Biologists measure Morro Bay’s eelgrass acreage each year. Eelgrass spanned 344 acres as recently as 2007 but had dwindled to just 14 acres by 2017. Not surprisingly, Roser’s 2016-17 brant survey recorded a population high of just 319 birds and a low of 43. Roser’s brant-use-day metric has fallen by 90 percent since the nearly 500,000 brant use days he recorded in 2001. In the past five years, brant use days have measured around 50,000 a year. Money from the purchase of the California duck stamp-validation, required to hunt waterfowl in California, is funding research into the eelgrass decline along with restoration efforts.

In addition to fewer numbers of brant frequenting Morro Bay, Roser has noticed behavioral changes in the birds that still show up. Increasingly, the brant are foraging on secondary food sources that include salt marsh vegetation and green algae species such as sea lettuce with eelgrass in short supply.

Roser takes some solace that the overall Pacific Flyway brant population is holding steady if not increasing, estimated between 130,000 to 165,000 birds. Roser says waterfowl biologists are seeing flyway-wide changes in brant behavior that they suspect may be linked to climate change.

Fewer brant are migrating to Mexico for the winter. More are remaining in Alaska and their northern range throughout the year as warming Arctic conditions require fewer calorie demands and less ice exposes more eelgrass. Ten years ago, less than 10 percent of the population wintered in Alaska. By 2017, almost 40 percent of the Pacific Flyway population spent the winter there.

“This bird is tied to Morro Bay, our culture and our identity,” Roser said. “A robust wintering brant population needs abundant eelgrass beds. Eelgrass needs a healthy bay and watershed. Our actions as stewards of Morro Bay really do reverberate across the globe.”

CDFW photos: courtesy of John Roser
Top photo: Pair of black brant on Morro Bay



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