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, surveys in 2017 showed phalarope numbers
declined by 78% compared to pre-restoration baseline monthly summer average of 3225 birds has
warranted ongoing phalarope studies. 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 2022 migration.
From June 21, 2022 to September 27, 2022, we conducted phalarope migration surveys at 31 sites (17
SBSPRP-managed former salt ponds, 7 Cargill-managed salt production ponds, and 7 additional non-salt
pond sites). The surveys found that counts of Wilson’s phalaropes peaked at 735 phalaropes on 07/19/22
and counts of red-necked phalaropes peaked at 4357 phalaropes on 08/30/22. Across all sites, a total of
13039 phalaropes were counted throughout the summer (1100 Wilson’s, 11032 red-necked, and 907 that
could not be identified to species). Looking only at the 24 current and former salt pond sites within the
study area, a total of 8698 phalaropes were counted throughout the survey season (2 Wilson’s, 7896
red-necked, and 755 that could not be identified to species). The total and peak counts for Wilson’s
phalarope were similar to 2021 data while the total and peak counts for red-necked phalaropes were both
somewhat lower. The proportion of unidentified phalaropes relative to total observations decreased
slightly from 2021 and continues to be a complicating factor in species-level analysis, but taking the
measure of assigning them to the most likely based on survey date does not change the peak counts/dates
or the direction of the trends for season totals for either species. Calculations to compare these survey data
against the NEPA/CEQA baseline show that phalarope abundance continues to be below the management
trigger of more than 50% below baseline values.
At the pond-level, phalarope abundance did not align with expectations around their preference for
high-salinity ponds. The majority of phalaropes (96%) were found in medium- and low-salinity sites,
suggesting that they may be using different selection criteria. As the SBSPRP progresses, we recommend
a precautionary approach to waterbird habitat management and tidal marsh restoration. To the extent
feasible, ponds within the project area should be maintained to provide a variety of salinity and water
levels suitable for different guilds. Given the limited number of ponds that can be maintained under sea
level rise, studies are needed to identify the specific salinity and water level characteristics that cannot be
provided by restored tidal marsh for habitat specialist species. Special consideration should be given to
understanding what influences phalarope site selection and preserving ponds with those characteristics.
Continued dedicated monitoring of phalaropes and analysis with habitat and external regional datasets
will be valuable in assessing the decline in survey counts since pre-restoration baselines. Future phalarope
migration surveys are needed to estimate inter-year changes in abundance that could be used to assess the
relative importance of broader-scale climatic drivers (or breeding ground conditions) versus local management and habitat characteristics on the observed declines. Few phalaropes were observed during
the new June survey date, but these surveys allowed us to definitively identify the peak of migration,
which was not possible in 2021 because the highest counts that year were in early July (the previous first
survey date). Future study of Motus data when it is available will aid in estimating population sizes and
understanding phalarope migration between stopover sites.
