Executive Summary
The South Bay Salt Pond Restoration Project (SBSPRP) is restoring over 15,000 acres of former salt evaporation ponds to a mix of tidal marsh and ponded wetland habitats. These wetlands provide habitat for many waterbirds, including migrating Red-necked Phalarope (Phalaropus lobatus) and Wilson’s Phalarope (P. tricolor). Sustaining baseline population goals for wildlife populations requires understanding how species are responding to restoration actions over time. While many waterbird guilds have increased in abundance from pre-restoration baselines, phalarope numbers have declined >50% below baseline numbers. The purpose of this ongoing study is to understand observed declines in phalarope numbers within the SBSPRP area and their relationship with broader population trends and phalarope movements. This report serves as a data summary and coarse-scale assessment of phalarope monitoring efforts in the South San Francisco Bay during the 2025 migration.
From 2023-2024 large sightings (>1,000 birds in some cases) were observed on ponds outside of the set of 31 sites initially believed to be sufficient to capture >95% of recent phalarope sightings. In the previous report, we therefore reanalyzed the historical data from the full 2002-2024 dataset and identified those sites that may also support significant numbers of phalaropes. From this list, this year we nearly doubled our survey effort by surveying 27 new ponds: A10, A11, A14, A15, A16, A22, A23, A3W, A5, A7, A8, E10, E11, E14, E1C, E2C, E3C, E4C, E6C, M4, M5, M6, N3, R3, R4, R5, and RSF2U3 (in addition to E5C which was added in 2024).
From June 17, 2025 to September 25, 2025, we conducted 8 rounds of phalarope migration surveys at 59 sites (41 SBSPRP managed ponds, 11 Cargill-managed salt production ponds, and 7 sites outside of these areas). Across all sites, a total of 9,066 phalaropes were counted throughout the summer (3,498 Red-necked, 3,583 Wilson’s, and 1,985 that could not be identified to species). Compared to last year, this was 4,231 more sightings of phalaropes (+1,065 Red-necked, +2,231 Wilson’s, and +935 that could not be identified to species). Counts of Wilson’s Phalaropes peaked at 1,324 phalaropes on July 1st and counts of
Red-necked Phalaropes peaked at 1,894 phalaropes on September 9th.
Looking at only the 52 sites within SBSPRP and salt pond area, a total of 6,871 phalaropes were counted throughout the survey season (3,347 Red-necked, 1,542 Wilson’s, and 1,982 that could not be identified to species). Within only the SBSPRP and salt pond complexes from the early July through end of September surveys, the average number of sightings of phalaropes per survey was 982. This was -81.6% below the revised 2005-2007 baseline of 5,324, and counts therefore remain below the Adaptive
Management Plan trigger threshold of a decline of 50% or more below baseline values.
Across all new sites, the only phalaropes sighted were 33 Red-necked Phalaropes, all of which were seen during the late August survey at just three sites: A8 (17 birds), A15 (7 birds), and E3C (9 birds). This suggests that the core set of 32 sites, though imperfect, is largely sufficient for capturing the key trends.
To increase confidence in this conclusion, we recommend continuation of phalarope migration surveys at the expanded set of sites in 2026 to confirm this initial finding of a lack of phalaropes. In future years, the set of sites may be able to be winnowed down again. The mid-June migratory period was added in 2022 because the peak count of Wilson’s Phalaropes in 2021 was in early July, the previous first survey window, creating uncertainty in whether this was the true peak. This mid-June survey period has only had 68 phalarope sightings across all four years since then (0.2% of all sightings). This survey is also not conducted at any other staging sites. It therefore appears unlikely that this survey window is necessary and we recommend removing it from the protocol in order to reduce the cost of monitoring.
The recent range-wide modeling report showed a growth in phalarope peak abundances across their entire range of 5–25%, indicating that while the partial recovery of San Francisco Bay abundances may have benefited from range-wide increases, they exceeded rather than simply tracked global trends. The largest increases in abundance were all outside of the SBSPRP (M2, M1, Crittenden Marsh, N2, and N1), with the exception of A9, which had 557 more sightings this year and was the third-most abundant site. This aligns with the predictions of the change model, which predicted that shifting hydrology would drive a reduction in abundance in the SBSPRP that would be outweighed by an increase in the other sites.