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October 29, 2024

Follow an American Avocet for one year with the U.S. Geological Survey's bird tracking data.

The U.S. Geological Survey - USGS – along with partners across the western U.S., are tracking hundreds of migratory water birds in the Great Basin to try and answer some complicated questions. Why do migratory and other waterbirds choose to use the terminal lake and wetland habitats they do in the Great Basin? What is it about these lakes that make them so important to these birds? Connecting detailed bird movement data with water quality and quantity, and prey availability is vital information for water, land, and species management. 

One waterbird of interest is the American Avocet, a protected species under the Federal Migratory Bird Treaty Act. American Avocets use the Pacific and Central flyways throughout the year. During the breeding season American Avocets form monogamous pairs and often land in the Great Basin to nest. The paired birds make their nests on the ground without any vegetation for shade and take turns incubating and defending the eggs for about a month. Within a day of hatching, the chicks can walk, swim, and maneuver enough to evade predators. Their parents are free to migrate or build another nest. 

American Avocet (Recurvirostra americana) on Great Salt Lake, Utah, USA

GPS tagging water birds

The Saline Lake Ecosystems IWAA Waterbird Movement Project has tagged over 100 American Avocets since March of 2023. One Avocet, a male identified as AMAV39, got its GPS tracking “birdie backpack” on June 10th, 2023, at the Summer Lake State Wildlife Area in southern Oregon. Researchers set a trap around his nest of four eggs. When AMAV39 came back to check the nest, a spring net gently closed around him to capture him while the researchers prepped the tagging equipment he would carry on his back for at least the next 12 months. 

The GPS equipment is lightweight and not harmful to the birds, but attaching a GPS tag does not always guarantee long term movement data. The tracking equipment is solar powered, but the battery can malfunction. The equipment relies on the cellular network infrastructure, and coverage varies depending on the bird’s location. Or a predator could get the bird before it can continue its journey. If all goes well, valuable data in understanding the bird’s habitat use are obtained, and the birds are not stuck with the trackers the rest of their lives. The harness material will wear out and fall off within a couple years. 

“We are putting cellular tags on birds in the Great Basin which has arguably the least cellular coverage in the country. Habitat and weather conditions in the Great Basin vary widely. And we are marking species that no one even has a half an understanding of what they do when they move from one place to another. Each cellular tag deployment is a sort of “fingers-crossed-knock-on-wood" release into the unknown. We anxiously await more data as the birds pass in and out of cellular coverage and give us glimpses into their secret lives.” -Cory Overton, USGS Wildlife Biologist. 

USGS Wildlife biologists pin down a spring-loaded net into the soil over an American Avocet’s nest in Malheur National Wildlife Refuge. Biologists capture the bird to take physical measurements and to attach a GPS tracking device. Once the bird is gently removed from the net, its culmen, or bill, is measured from the tip of the beak to the feather line using digital calipers. Still using the calipers, the bird's legs are measured. Lastly, the wing length is measured with a ruler. These basic measurements can be useful to identify species, identify difference between the sexes, age, or otherwise characterize individual birds. After measurements are taken biologists attach the lightweight square-shaped GPS tracker with elastic bands. Once the device is attached, like a birdie backpack, the Avocet is released and takes flight.

Summer Lake: A large, shallow, alkaline lake in southern Oregon, within the Northern Great Basin

After AMAV39 got his tracking backpack, he remained at Summer Lake to tend his nest and forage off the lake and wetland resources until the end of September 2023. Summer Lake is ideal habitat for many waterbirds and hosts a spectacular array of birds each season luring spectators and wildlife photographers. Summer Lake’s main source of freshwater is the spring-fed Ana River.  Ana River flows from the base of Winter Ridge in Lake County, seven miles to Summer Lake. 

When water is plentiful, Summer Lake can be about 15 miles long, 5 miles wide, and cover around 38,000 acres, with a maximum depth of 5 to 7 feet. However, water levels can fluctuate dramatically, and this level has rarely been reached in recent years. The flow from Ana Springs decreased due to the impoundment of the river and submergence of the spring outlet in 1923, along with increased water use for irrigation. As a result, there is less inflow to the lake. The lakebed is often dry during many summers since 1923.  

A sequence of satellite imagery of Summer Lake in southern Oregon from May – July 2024. In May the lake is full and deep-blue in color. As the satellite images progress through time Summer Lake shrinks dramatically as water evaporates. By July the lake has dried out completely and only some marshlands remain.
Summer Lake, Oregon

Lake Abert : A large, shallow hypersaline lake in southern Oregon, within the Northern Great Basin 

After AMAV39 ended his time at Summer Lake, he flew 20 miles southeast to Lake Abert and remained there for almost a month into late October. Lake Abert is Oregon’s only hypersaline lake. It’s an important stop over for birds during the spring and fall migration. AMAV39 likely spent the month resting and feeding on the alkali flies and brine shrimp that live in the expanse of shimmering, salty water.  

The Bureau of Land Management considers Lake Abert an Area of Critical Environmental Concern, but the lake itself does not have water rights. Water rights refer to the legal entitlements that individuals or organizations have to use water from a particular source, such as rivers, lakes, or groundwater. Upstream withdrawals from the Chewaucan River can leave Lake Abert with minimal to no water – this can create conditions too salty for even the brine shrimp and other species in the complex food web. Removing food sources from a critical habitat like Lake Abert can destabilize an entire ecosystem. If this would have happened in October 2023, where would AMAV39 and thousands of other water birds have found food? 

shallow water come up against a rocky sloped shoreline dotted with green shrubs
Lake Abert, Oregon is one of the 20 terminal lakes identified by USGS partners as priority ecosystems for study by the Saline Lakes Ecosystems Integrated Water Availability Assessment.
shallow blue lake water with a small fountain bubbling the water. Arid landscape with rolling hills and blue-sky.
To control dust storms from the dry lakebed sprinkler systems spray water to rehydrate Owens Lake.

Heading south for the winter

As the days shortened and the temperatures began to drop, AMAV39 felt the ancient call to fly south for the winter. On October 24, 2023, he made a quick pit stop at Goose Lake on the Oregon/ California border. Then another couple of hours of rest at Carson Lake, Nevada before heading even further south. 

After a rapid trip - 193 miles at 32 miles per hour – straight through southern Oregon to California, AMAV39 took a well-earned break at Owens Lake in central California. Owens Lake is not a historically dry lake, but it became one when the Los Angeles Aqueduct was constructed in 1913, routing its waters to Los Angeles. The dry lakebed fueled massive dust storms that became an air-quality hazard. To control the dust, water is now pumped back into Owens Lake. Brine shrimp, brine flies, and other food sources began to occupy the portions rehydrated lakebed, and some birds returned. As a bi-product of dust control, in the early 21st century Owens Lake once again became an important stop-over and nesting ground for migratory birds, as is evident by AMAV39’s lengthy one month stay. 

 

In late November, while many Americans were preparing for Thanksgiving, AMAV39 resumed his southward flight, crossing into Mexico for a feast of his own at the Colorado River Delta. AMAV39 made the 383-mile trek in a single day on November 20th, 2023. 

For much of the 20th century and into the early 21st century, the Colorado River rarely, if ever, reached the ocean. The river's flow was heavily diverted for agricultural, industrial, and urban use, particularly in the southwestern United States and northern Mexico. This intense water usage, coupled with the construction of large dams like the Hoover and Glen Canyon Dams, significantly reduced the river's flow downstream. Yet after years of restoration, grass roots efforts, and international agreements between the U.S. and Mexico allocating water back to the environment, the Colorado River reaches the ocean once again. AMAV39 and many other birds can now rest and refuel on patches of salt grass in the delta’s estuary.  

satellite image of a thin, brown, winding river merging into a blue-green ocean delta
High resolution satellite image of the Colorado River Delta in Mexico.

By the end of November, AMAV39 made it down the Gulf of California, having several small stops along the way, and reached his southernmost winter habitat at the Marismas Nacionales–San Blas mangroves. The Marismas Nacionales is a network of lagoons and wetlands covering 770 square miles in the Mexican states of Nayarit and Sinaloa. This area is home to more than 250 species of birds throughout the year. AMAV39 stays in this lush paradise until mid-December then starts heading northward. 

Mangrove, La Tovara National Park, Ramsar Site, Wetlands of International Importance, San Blas Town, Matanchen Bay, Pacific Ocean, Riviera Nayarit, Nayarit state, Mexico, Central America, America

Return to the Great Basin  

AMAV39 took a slow route back to the United States. He meandered between several lakes and coastal estuaries along the west coast of Mexico - often taking several weeks to rest. Many of you likely wish you could wait out the cold winter and spring in a similar fashion.  

At long last, after 4 months away, AMAV39 cruised back into U.S. airspace on April 17th, 2024. He refueled at the Salton Sea in southern California and flew an incredible 230-miles in a single day to return to Owens Valley, CA. 

After almost two weeks in Owens Valley, AMAV39 felt the call to breed and quickly made his way north. He stopped for a few days to enjoy the wetlands around Carson Lake, Nevada and the alkali lakes of Surprise valley in northeastern California. 

On May 2, 2024, AMAV39 reached Summer Lake where it had been tagged almost a year earlier. After finding a monogamous partner for the season, the two love birds bunkered down to nest. Water and food were apparently abundant enough at Summer Lake for AMAV39 and his partner to settle down between May and July, 2024 and nest only a few hundred yards away from last year’s nest location. 

AMAV39 hit a lot of important habitats in his annual trek south and back north. Every water body he stopped at has a story of habitat loss, water scarcity, and sometimes incredible restoration efforts. His journey shows the delicate balance of nature and the interconnectedness of ecosystems across vast distances. From the wetlands of Summer Lake to the mangroves of Marismas Nacionales, each stop provided crucial resources that enabled this magnificent traveler to complete his epic, 3690-mile migration.  

American Avocet 39’s (AMAV39) year long journey detailed by U.S. Geological Survey (USGS) GPS tracking data. AMAV39’s flight path, represented by a purple line, starts in the Great Basin at Summer Lake in July 2023 then heads to Lake Abert in October 2023. Between October – December 2023 AMAV39’s flight path zooms down the Western United States to its winter nesting grounds at the Marismas Nacionales–San Blas mangroves in Mexico. In January 2024 AMAV39 slowly makes its way back north along the west coast of Mexico into the Western United States. In July 2024 AMAV 39 returns to its former nesting grounds in the Great Basin at Summer Lake. In total AMAV39 flew 3,690 miles. View the bird movement data release.

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