​Spearheaded by Amy Parsons, SFBBO’s Lead Waterbird Biologist, the new 2025 Colonial Waterbird Monitoring Report summarizes what our community scientists found across 76 active nesting colonies across 82 sites spanning from northern Napa Valley to Santa Cruz. Our monitors documented 2,741 heron, egret, and cormorant nests and 747 tern and shorebird nests—with Double-crested Cormorants as the most abundant nesting species. Some of these rookeries were impressively huge: Dover Park hosted over 250 nests of Snowy Egrets and Black-crowned Night-Herons, and the Alviso pond complex continued to support large concentrations of cormorants, terns, and shorebirds. 

​Behind the scenes, we also developed a new mathematical algorithm to estimate fledgling production from our simplified field protocols. For the first time, we can say that the huge Great Egret colony at Gold Hill produced an estimated 284 fledglings! Because our volunteers can't follow individual nests through their entire lifecycle, we needed a way to correct for double-counting slow-developing chicks on consecutive visits and account for nests hidden by foliage that we know are there but can't always see. The result is a more rigorous estimate of breeding success that we can apply consistently across all our sites going forward, strengthening the scientific value of the dataset even as we've made fieldwork more accessible. Those key measures are going out to both federal agencies like the U.S. Fish and Wildlife Service and local ones like Santa Clara County Parks to help guide their conservation of these keystone birds and their habitats.

​One of the report's most significant stories is about California Gulls, a species that has a reputation of being a management headache in the South Bay for their tendency to predate nests of threatened birds like Snowy Plovers. But here's where it gets complicated: did you know California Gulls were once also listed by the state as a bird of conservation concern? Their native breeding grounds are at Mono Lake, a salt lake with specialized habitat that they need, and which has long been threatened by unsustainable water withdrawals to Los Angeles. It wasn’t until a few decades back when they were delisted because of the explosive growth of the San Francisco Bay population and an apparent stabilization of Mono Lake’s water levels. But with Mono Lake plagued by continuing water overdraft that has driven collapses in invertebrate prey, our partner scientists there reported 2024 had the lowest-ever count (just 20,258 birds) with chick production collapsing by 97%. Back here in the Bay, our walkthrough surveys found 36,820 breeding adults across 9 colonies in 2025, a 9% decline from the previous year and part of a broader years-long plateau.

​Our local population may represent over 60% of the entire state's breeding birds and roughly 10% of the global population. With South Bay now supporting more breeding California Gulls than Mono Lake, it is a potentially important refugia for California Gulls, even as they pose a risk to the nests of Forster's Tern, American Avocet, and other sensitive waterbirds. Land managers face the genuinely difficult task of protecting rare shorebirds from gull predation while recognizing that the Bay Area may be this species' most stable breeding ground in all of California. There are no easy answers, but in May we will get in our kayaks to head back out to the gull colonies to continue gathering the long-term data needed to navigate this tricky situation. 

​None of this would be possible without our extraordinary community scientists. In 2025, 118 volunteers contributed over 1,000 hours. That’s equivalent to more than $40,000 in donated labor! They spent their weekends peering through spotting scopes, counting nests, recording disturbances, and building the kind of long-term dataset that no single research team could maintain alone. To every one of you: thank you!!

And now we're gearing up for what promises to be our biggest season yet. The 2026 nesting season launches in earnest, with over 100 volunteers trained and ready to head into the field. It's the largest monitoring effort in the program's history. That said, we still have a few colony sites in the North Bay that need dedicated monitors. If you or a birder you know in Marin, Sonoma, or Napa County would like to contribute to real conservation science while getting to know your local waterbirds intimately (or if you’re in South Bay and want to join us for California Gull Walkthroughs in May) just email Amy to get involved!

​Salt-tolerant stands of pickleweed, salt grass, alkali heath, marsh gumplant, and salty susan will provide habitat for a variety of species at the toe of the levee, and large patches of salt grass placed along the mid-slopes of the levee will provide low, invasion-resistant grassland for foraging birds. A few tidal and tidal-adjacent areas were planted with a greater diversity of plants often found in upland areas adjacent to marshes. The hard-working members of the San Jose Conservation Corps helped the hard-working members of the Habitats team complete the planting over a period of about 2 months. The rest of the levee was treated with a mix of native seeds; goldfields, tidy tips, red maids, and fiddlenecks are currently blooming in great abundance.

​Happily, this was the case for the project I was finishing on New Year’s Eve 2025. The Plover and Tern Program at SFBBO received a Section 6 grant from the US Fish and Wildlife Service and the California Department of Fish and Wildlife in August 2024 that provided funding for our biologists to deploy Motus tags on western snowy plovers at Eden Landing Ecological Reserve in Hayward. Although Motus tags have been used on snowy plovers in the Great Salt Lake and Mexico, our project is the first one to deploy them on the federally listed population. We were also testing an aspect of the technology that would allow us to track finescale movement within individual ponds. We partnered with two additional snowy plover biologists in the Bay, Ben Pearl, who longtime readers may recognize as the former Plover and Tern Program Director at SFBBO, and Carleton Eyster, a renowned plover biologist who has been studying the species since the 1990s.

​After a year of hard work that involved 12-hour build days, walking 40 grams of raw chicken on the end of a tripod across Eden Landing, waiting at nests until 1am to capture adult male plovers, and sorting through 5 million lines of data, we had arrived at the finish line. What did we have to show? ​Many interesting things!

​Incubating plovers spend a lot of time at their nest. On first glance, this seems obvious. Of course they’re spending a lot of time at their nest, where else would they be? But plover pairs typically divide their incubation duties into shifts. The males are supposed to incubate at night and the females are supposed to incubate during the day. This allows the other sex to leave and forage or roost for half the day. During our regular daytime surveys, we usually observe the female on the nest by herself and the male is nowhere to be found. However, the Motus data showed that while the other adult did leave and forage when they weren’t incubating, they still spent a lot of their “free time” near the nest. This also allowed them to sneak in short incubation stints even when they weren’t “supposed” to be incubating. This shows that the day/night split between females and males is not so straightforward and is likely unique to each pair.

​Plovers really love water! A trend we noticed immediately is that when birds weren’t at their nests, they were finding a wet area of a pond to forage along. This makes sense when you consider that plovers are shorebirds. They’re adapted to eat small invertebrates that occur along the tideline. It makes perfect sense that they would seek out the water’s edge on salt ponds as well. SFBBO has always understood that good foraging habitat includes water, but this project really helped us visualize just how much time plovers spend foraging. The plover program is primarily focused on ensuring plovers have adequate breeding habitat in the Bay Area, and while that is definitely still important, this project has inspired us to think about foraging habitat more intently as well.

​And finally, some of the birds we tagged went to many different places! The Motus tags that we used don’t just tell us information about where individuals are in Eden Landing, they can also ping any other Motus tower in the world. From pings we received from towers outside Eden Landing, we know that our birds have gone to Point Reyes, China Camp State Park, Don Edwards National Wildlife Refuge, Milpitas, Napa-Sonoma Marshes Wildlife Area, and the Channel Islands! We have always known that plovers disperse to a variety of areas in the winter, but it was so exciting to see just how many different places they went.

As a biologist, I spend so much time staring through a scope, hoping to get a quick peek into a plover’s life, knowing that it is only a tiny snapshot, and accepting that I will never get to see the vast majority of their life. It’s not that typical survey methods don’t work or are inadequate: I am consistently amazed by how much information we’re able to acquire from a weekly survey alone. But when the opportunity comes along to crack open the puzzle a little wider and peer into the vast network of interactions we call ecology, it’s impossible not to feel the excitement. The maps that we generated from the Motus data and included in the final report for this project took an astronomical quantity of information and condensed it into a representation that our human brains can easily interpret. When I look at one of these maps and understand the habits of a tiny bird that I may have never seen with my own eyes, it feels like magic.