A pair of banded snowy plover chicks. Santa Barbara Zoo, USFWS Pacific Southwest Region (Flickr)
A group of snowy plovers runs across a dry salt pond at the edge of the south San Francisco Bay, brightly colored plastic bands visible on some of the birds’ legs. They stop moving, ducking down into small depressions in the ground, becoming almost invisible except for their heads peeking out at the flat landscape around them.
Weighing just one to two ounces, these tiny birds make their homes on dry salt flats and sandy beaches. Living in such exposed habitats can bring dangers, including human disturbance and predator attacks, and the shorelines they call home have been impacted by coastal development and will see losses from sea level rise in the coming decades. Due to these threats, the Pacific coast population of snowy plovers was federally listed as a threatened species in 1993 under the Endangered Species Act. Their population remains threatened today, with only about 2,500 breeding adults present across the Pacific coast. The colorful bands on their legs are part of efforts to save them.
A recently hatched snowy plover chick and unhatched egg. Alexis Frangis/California Department of Parks and Recreation, USFWS Pacific Southwest Region (Flickr)
“Color banding is a tool that we use in order to learn more about snowy plover chick survival, recruitment into the population, and migration,” says Ben Pearl, Science Director at the San Francisco Bay Bird Observatory (SFBBO) and the leader of SFBBO’s plover program. Every spring, during plover breeding season, biologists from SFBBO attach bands to the legs of recently hatched chicks. They also band some adult birds, allowing them to also track their survival and movement, as well as “to better understand how they’re using habitat,” says Pearl. Knowing where the birds go and how many of them survive year to year provides valuable information for habitat restoration and other conservation efforts.
The process of banding requires careful observation and knowledge of when chicks will likely hatch. Plovers rely on camouflage for protection, so spotting them isn’t easy. During some months of the year, Pearl and others on SFBBO’s plover team spend most of their days searching for plovers and carefully noting their observations. When the team spots a bird incubating eggs, they go out to the nest to determine the eggs’ age. They’ll then return to the nesting site around the predicted hatch date, closely monitoring the eggs and trying to band the chicks within 24 hours of hatching, when they’re easier to catch. Each bird gets two bands on each leg in a unique color combination. This allows biologists—as well anyone who spots one of these birds—to identify the individual without having to catch it again, by noting the band color pattern.
A snowy plover chick being banded. Santa Barbara Zoo, USFWS Pacific Southwest Region (Flickr)
One of Pearl’s favorite plovers has black and orange bands on one leg and green and yellow on the other. Pearl calls this male the “Bay Area baseball bird,” since its colors match those of the Bay’s two professional baseball teams. He was banded as an adult in Menlo Park, and is known—from sightings and recordings of his band colors—to spend his winters at Ocean Beach in San Francisco. He comes back to the Bay Area to breed each year and has been spotted at various sites, most recently in Mountain View. As Pearl states, this bird “tells the story of how much information this banding can really provide for us.”
A specific piece of data that banding allows SFBBO to collect is plover chicks’ “fledge rate,” or the percentage of banded chicks that survive until they’re 28 days old and can begin to fly. In 2021, SFBBO calculated a fledge rate of only 31 percent for snowy plovers in the Bay Area. Though this is likely a conservative estimate—the chicks’ camouflaging abilities make it hard to spot them and read their bands—this rate is too low to indicate steady population growth. In 2022, the Bay’s recorded snowy plover population was 288 adult birds—the highest number SFBBO has ever recorded. But, Pearl states, “the goal for the San Francisco Bay...is 500 adults. So we’re a little bit over halfway there, but we definitely have a lot of work to do in order to meet those recovery goals.”
Having detailed knowledge of how well plover populations are doing, as well as where they live and breed, is very important for their restoration efforts. In the Bay, the data that SFBBO collects influences work on the South Bay Salt Pond Restoration Project, an effort to restore former salt ponds to tidal marshland. Healthy marshland is very important, both for the animals that live in it and for nearby human communities. But, because plovers—as well as other bird species—breed, rest, and sometimes feed in the salt flats, the loss of this habitat as it is restored to marshland could negatively impact these species. To combat this, Pearl says, SFBBO works to “maximize the remaining habitat that’s left that’s going to be managed as dry ponds” as the salt pond restoration project progresses.
As Pearl and his team look to the future, he says that they hope to continue to “provide higher quality habitat” for the plovers so that more of the birds have safe places to breed and grow. In light of the continued threats that snowy plovers face, SFBBO’s work to survey, band, and enhance habitat for these birds remains of great importance for their recovery in the years to come.
A banded adult snowy plover. Channel City Camera Club (Flickr)
Sources:
SFBBO, “Plover and Tern Research”: https://www.sfbbo.org/ploversandterns.html
“Snowy Plover Monitoring in the San Francisco Bay Estuary”: https://www.youtube.com/watch?v=saPw9FJEuZo
“Snowy Plover Conservation in the Bay Area by Ben Pearl”: https://www.youtube.com/watch?v=Q_cbiGg24YM
“SFBBO biologists release four rescued Snowy Plovers”: https://www.youtube.com/watch?v=kIH0gMeP5VQ
SFBBO, “Western Snowy Plover Monitoring in the San Francisco Bay Annual Report 2021”: https://www.sfbbo.org/uploads/1/1/6/7/116792187/western_snowy_plover_monitoring_in_the_s an_francisco_bay_annual_report_2021.pdf
The Cornell Lab of Ornithology, “Snowy Plover”: https://www.allaboutbirds.org/guide/Snowy_Plover/overview
Monterey Bay Aquarium, “Western snowy plover”: https://www.montereybayaquarium.org/animals/animals-a-to-z/western-snowy-plover
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Erin Cole is a master’s student in the Environmental Communication program at Stanford and completed her bachelor’s degree in Earth Systems at Stanford last June. She is passionate about environmental education and marine science and hopes to work at the intersection of these fields after graduation. In her free time, she enjoys tidepooling, hiking, reading, and making crafts.
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