Nathan Van Schmidt

Lunch and Learn Science: Spin Cycle: Decoding population dynamics of phalaropes and other waterbirds - Nathan Van Schmidt, SFBBO

ariela — Mon, 24 Mar 2025 23:12:59 +0000

Lunch and Learn Science: Spin Cycle: Decoding population dynamics of phalaropes and other waterbirds - Nathan Van Schmidt, SFBBO

Presentation introductory slide

ariela Mon, 03/24/2025 - 16:12

Presentation

Description

On March 11, 2025, as part of the 2024-25 Restoration Project Lunch and Learn Science Speaker Series, Nathan Van Schmidt of the San Francisco Bay Bird Observatory laid out the challenges facing waterbirds of the Pacific Flyway within the Restoration Project and shared more than two decades of monitoring data on phalaropes and other foraging guilds including shorebirds, ducks, and terns.

See the Event page for more information.

Author(s)

Nathan Van Schmidt

Date

Tue, 03/11/2025 - 11:00am

South Bay Salt Pond Waterbird Surveys, September 2022 – May 2023

ariela — Wed, 19 Feb 2025 19:04:36 +0000

South Bay Salt Pond Waterbird Surveys, September 2022 – May 2023 ariela Wed, 02/19/2025 - 11:04

Document Category

Scientific Reports

Author(s)

Nathan Van Schmidt

SFBBO

Date

2023-10

Summary

REVISED FINAL REPORT

Suggested citation: Van Schmidt, Nathan D. 2023. South Bay Salt Pond Waterbird Surveys: September 2022–May 2023. Report prepared for the South Bay Salt Pond Restoration Project.

Executive Summary
This report serves as a data summary and coarse-scale assessment of waterbird and water quality monitoring efforts at six pond complexes in the South San Francisco Bay. Coyote Hills, Dumbarton, and Mowry salt ponds are owned by Don Edwards San Francisco Bay National Wildlife Refuge and managed for salt production by Cargill Salt. Alviso and Ravenswood complexes are owned and managed by the U.S. Fish & Wildlife Service as part of the Don Edwards San Francisco Bay National Wildlife Refuge. Eden Landing Ecological Reserve (Eden Landing) ponds are owned and managed by California Department of Fish and Wildlife, with the exception pond CP3C, which is owned by Cargill Salt. This report is based primarily on data collected by the San Francisco Bay Bird Observatory between September 2022 and May 2023.

The purpose of this ongoing study is to describe avian use of ponds to guide regional waterbird conservation, management, and habitat restoration efforts. The South Bay Salt Pond Restoration Project (SBSPRP) is restoring 15,000 acres of former salt evaporation ponds to a mix of tidal marsh and enhanced managed pond habitats. Restoration and monitoring is entering its third decade, and long-term population analyses have shown declines in some species and guilds, but evidence of cyclical trends (regular increases and decreases) in others, which may be driven by climate patterns or density-dependent regulation. It is therefore important to determine the drivers of these long-term trends, and to contextualize local trends with population trends elsewhere in the range, to assess the likelihood that observed declines are driven by SBSPRP actions rather than other factors. Understanding how waterbirds use ponds, identifying key habitat associations, and incorporating features essential to pond-dependent species into restoration plans is important for helping maintain baseline numbers of waterbirds in the South Bay and recovering populations that have experienced long-term declines.

From September 2022 – May 2023, we conducted waterbird surveys and water quality sampling at 82 ponds (22 Cargill-managed salt production ponds and 60 SBSPRP-managed ponds). We examined species richness, abundance, and behavior of waterbird assemblages within and among pond complexes. We grouped species into guilds (e.g., dabbling ducks, diving ducks, gulls) based on foraging methods and prey requirements to understand waterbird use of these ponds. We used these data to assess long-term changes in waterbird numbers relative to baseline counts from before marsh restoration. We recorded 1,246,072 waterbird observations of 82 species (all sites combined). The Alviso and Eden Landing pond complexes supported the greatest species diversity and Alviso had the highest abundances of all complexes. The abundance of 5 out of 7 currently tracked species/guilds has increased in SBSPRP ponds since prior to restoration activities in 2005–2007 (6 of 8, if counting small shorebirds in both the fall and spring). Exceptions comprise Bonaparte's gulls, dabbling ducks, and medium shorebirds; plus phalaropes, which supplemental summer surveys show have declined. For most of the species/guilds that increased in abundance across all ponds, the increases are largely due to higher counts within the SBSPRP area. This indicates long-term benefits of the project for many waterbird populations within South San Francisco Bay. However, 6 of the currently tracked fall/winter/spring taxa have declined in recent years, which is cause for caution. Only small shorebirds are currently stable (slightly increasing in fall and slightly declining in spring).

Two species/guilds have declined below trigger values defined in the Adaptive Management Plan: Bonaparte’s gulls and phalaropes. In the previous year, Bonaparte’s gull had declined by 84% relative to their baseline abundance, crossing the adaptive management plan’s trigger threshold of >50% decline below the baseline in a single year, or >25% in three consecutive years. This winter, detections of Bonaparte’s gull had increased from the previous year to an average of 763, but this still represents a decline of -40% and the running average two-year decline is -62% (winter 2021 and 2022 seasons; winter 2020 was not surveyed due to COVID-19 restrictions).

Given that two other saline specialist guilds also show signs of decline within the SBSPRP area–phalaropes have passed the trigger level, and eared grebes remain in salt production ponds but have dwindled in the SBSPRP footprint–the loss of high-salinity habitats is likely one of the causative factors. We recommend special consideration should be given to habitat needs of phalaropes and Bonaparte’s gulls, but note that these are poorly understood within the South San Francisco Bay ecosystem. More focused field studies on their habitat use and selection are needed to identify their habitat requirements and understand how to manage them effectively to recover these populations. In the meantime, we recommend cautiously maintaining a variety of water quality parameter levels in order to support guilds with different habitat requirements.

Keywords

Pond Complex

Alviso

Eden Landing

Ravenswood

EDEN LANDING ECOLOGICAL RESERVE PILOT STUDY ON PREDATORS OF WESTERN SNOWY PLOVERS AND CALIFORNIA LEAST TERNS FINAL REPORT

Dave Halsing — Mon, 04 Mar 2024 15:30:51 +0000

EDEN LANDING ECOLOGICAL RESERVE PILOT STUDY ON PREDATORS OF WESTERN SNOWY PLOVERS AND CALIFORNIA LEAST TERNS FINAL REPORT Dave Halsing Mon, 03/04/2024 - 07:30

Document Category

Scientific Reports

Author(s)

Date

2024-02

Summary

The objectives of this study were to 1) determine whether avian and mammalian predator activity, density, and space use can be successfully detected and quantified using camera traps, 2) employ multiple field techniques to estimate the activity, density, and space use of the array of species that depredate snowy plovers, comprising both birds and mammals, 3) make a preliminary determination of the effect of predator removal on predation rates using camera-trap derived estimations in combination with existing data, and 4) conduct preliminary testing of 1-2 additional methods of predator management (i.e., fencing and raptor nest relocation) and measuring subsequent responses, if any, in predator activity and predation rates.

Keywords

western snowy plover

least tern

predation

Pond Complex

Eden Landing

Phalarope Migration Surveys June – September 2022

ariela — Wed, 31 May 2023 20:02:28 +0000

Phalarope Migration Surveys June – September 2022 ariela Wed, 05/31/2023 - 13:02

Document Category

Scientific Reports

Author(s)

Date

2023-04

Summary

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.

Keywords

Pond Complex

Alviso

Eden Landing

Ravenswood

Review and analysis of historical phalarope population trends

ariela — Wed, 31 May 2023 19:54:28 +0000

Review and analysis of historical phalarope population trends ariela Wed, 05/31/2023 - 12:54

Document Category

Scientific Reports

Author(s)

Date

2023-04

Summary

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.
If a species group is observed to drop below a sustained threshold or hit a single-year trigger
point below that baseline, the Project is committed to evaluating available data and considering
targeted management action. Part of this consideration is whether the decline is likely a result of
restoration actions. In 2017, phalarope counts were below their assigned trigger point. Now we
seek to understand how this observed decline in the salt ponds compares to broader population
trends throughout the phalaropes’ Western migration routes.

We reviewed a combination of existing scientific survey data and community science data to
gain insight into phalarope abundance and how it has changed over time. In July 1986,
coordinated Wilson’s phalarope surveys across migration stopover sites yielded peak counts of
741,000, including 40,000 (5% of the total count) in South San Francisco Bay. By the early
1990’s, peak Wilson’s phalarope counts at the three largest migration sites had dropped by 50%.
Range-wide data is not available for red-necked phalaropes, but it was estimated that
52,000–65,000 passed through Mono Lake each year during the early 1980’s.

The next regular scientific surveys of phalaropes at migration sites began in 2019 and are
ongoing. Counts have varied across years and no clear directional trends have emerged. The
Wilson’s phalarope peak count was highest in 2019 (370,770) and lowest in 2022 (just under
200,000). The red-necked phalarope peak count was highest in 2019 (296,731 birds) and lowest
in 2021 (124,048). In 2021, counts from SFBBO’s Phalarope Migration Surveys represented less
than 1% of the total counts during peak periods. The 2022 peak count for Wilson’s phalarope
(735 birds) represents a decline of 98% from the 1986 survey data.

The time period of greatest interest for our purposes (2005–2018) is part of the gap between
scientific surveys of phalarope numbers. To shed light on this period, we performed an analysis
of community science data submitted to the eBird platform. We used negative binomial linear
models to investigate trends in phalarope counts while controlling for survey effort at several
geographic scales, ranging from three Bay Area counties to the state of California. We found that
phalarope counts had declined steeply from the early 1970s to the late 1990s, and from then to
the present showed a continuing but more shallow decline. The three Refuge counties (Alameda,
San Mateo, and Santa Clara) had higher counts than the rest of California in the 1970s, but
declined more steeply in the following two decades. Analysis of only the most recent 20 years
(2002-2022) found no significant difference in estimated population trends between the Refuge
counties and the rest of California, although the nature of eBird data makes this a relatively
insensitive analysis.

Keywords

Pond Complex

Alviso

Eden Landing

Ravenswood

Bridging the gap between disparate phalarope survey methodologies to evaluate population status

ariela — Wed, 31 May 2023 19:47:55 +0000

Bridging the gap between disparate phalarope survey methodologies to evaluate population status ariela Wed, 05/31/2023 - 12:47

Document Category

Scientific Reports

Author(s)

Gabbie Burns

Nathan Van Schmidt

SFBBO

Date

2023-04

Summary

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.
As part of the Project’s Adaptive Management Plan, NEPA/CEQA baseline population levels
were calculated based on Salt Pond Survey data from 2005–2007, before major restoration
efforts began. If a species group is observed to drop below a sustained threshold or hit a
single-year trigger point below that baseline, the Project is committed to evaluating available
data and considering targeted management action. In 2017, phalarope counts were 78% below
the baseline value, which is well beyond the action trigger of 50% below the baseline of a
monthly summer average of 3225 birds.

In response to this observed decline, targeted Phalarope Migration Surveys were piloted in 2019
and have been implemented in 2020–2022 with the goal of better capturing phalarope counts
during their brief migration window through the Bay Area and the salt ponds. As these new
surveys and the Salt Pond Surveys use different protocols with different levels of detectability, it
would be misleading to simply compare raw Phalarope Migration Survey results to the baseline.
The goal of this report was to identify data analysis strategies that could best assess the new
phalarope migration survey data with respect to the original NEPA/CEQA baseline.

We calculated adjustments to both the Phalarope Migration Survey data and the original baseline
to control for differences in survey location, timing, and frequency. In situations where there
were multiple options for how to reconcile these differences, we performed each alternative.

The results demonstrate that in every case, the counts from 2020–2022 are more than 50% below
the NEPA/CEQA baseline, hitting the management trigger. For future comparisons, we
recommend using a revised baseline that includes September surveys to more closely align with
the new Phalarope Migration Survey protocol. We also recommend continued Phalarope
Migration Surveys until there are sufficient years of survey data to perform an advanced analysis
of the rate of population change and differences between the restoration sites and those external
to the Project area. At a minimum this requires at least one more year of Phalarope Migration
Surveys, to give us a total of three complete years, but the quality of results will improve with
further years. Additionally, surveys should be conducted before and after major changes to pond
state (e.g., drying or breaching) in order to understand the impact of restoration activities.

Keywords

Pond Complex