population

The South Bay Salt Pond Restoration Project aims to restore many former salt production ponds, now managed for wildlife and water quality, to tidal marsh. However, because managed ponds support large densities of breeding waterbirds, reduction of pond habitat may influence breeding waterbird distribution and abundance. We investigated habitat use associated with breeding, feeding, and roosting behaviors during the breeding season for American Avocets (Recurvirostra americana), Black-necked Stilts (Himantopus mexicanus), Forster’s Terns (Sterna forsteri), and Caspian Terns (Hydroprogne caspia) in south San Francisco Bay in 2019 after substantial tidal marsh restoration, and compared results to a 2001 survey (before restoration). In 2019, managed ponds (26% of currently available habitat) were selected by waterbirds engaged in breeding behaviors (> 39% of observations), foraging (> 42%), and roosting (> 73%). Waterbirds avoided tidal habitats (43% of available habitat), comprising < 17% of observations of breeding behavior, < 28% of foraging observations, and < 13% of roosting observations. Waterbird densities increased in managed ponds between 2001 and 2019, and decreased in active salt ponds, especially among feeding Avocets (92% decrease) and Stilts (100% decrease). Islands were important for waterbirds observed breeding and roosting (45% of Avocet and 53% of Tern observations). Avocets and Stilts fed primarily on wet bare ground (65% and 58%, respectively), whereas feeding Forster’s Terns and Caspian Terns used mostly open water (82% and 93%, respectively). Within ponds, Avocets were associated with islands (131 m closer than expected). Stilts and Forster’s Terns were also associated with islands (68 m and 161 m closer than expected), except when feeding (1 m closer and 90 m farther than expected). Avocets and Stilts were associated with pond levees (39 m and 41 m closer than expected), but Forster’s Terns were not (9 m closer than expected). Our results emphasize the importance of managed ponds for breeding and foraging waterbirds, including islands for breeding and roosting and levees for foraging.

Keywords

birds

waterbirds

Pond Complex

Alviso

Eden Landing

Ravenswood

Content available here

eScholarship link to paper

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)

Gabbie Burns

Katie LaBarbera

Nathan Van Schmidt

San Francisco Bay Bird Observatory

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)

Katie LaBarbera

Gabbie Burns

Nathan Van Schmidt

San Francisco Bay Bird Observatory

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

San Francisco Bay Bird Observatory

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

Alviso

Eden Landing

Ravenswood

Coordinated phalarope surveys at western North American staging sites, 2019-2020

ariela — Sat, 16 Oct 2021 23:30:45 +0000

Coordinated phalarope surveys at western North American staging sites, 2019-2020 ariela Sat, 10/16/2021 - 16:30

Document Category

Scientific Reports

Author(s)

Date

2021-03

Summary

Wilson’s and red-necked phalaropes (Phalaropus tricolor and P. lobatus, respectively), have
poorly understood conservation statuses. These species breed in northerly latitudes of North
America to migrate to staging areas at saline lakes in western North America, before migrating to
South American lands and waters. Given saline lake habitat is threatened worldwide by water
diversion and climate change, there is an urgent need to better understand phalarope population
and trends. We conducted coordinated monitoring of western North American staging areas of
historical importance to phalaropes: Great Salt Lake (Utah), Mono Lake (California), Lake Abert
(Oregon), Owens Lake (California), south San Francisco Bay (California), and Chaplin Lake
(Saskatchewan). We conducted surveys at each site during week-long “survey windows,” from
mid-July to mid-September, 2019 and 2020, with the goal of at least one survey per site per
window. Methods were standardized within sites but varied across sites, including plane-based,
boat-based, and land-based surveys. We report results from Great Salt Lake, Mono Lake, and
Lake Abert in 2019 and for all surveyed sites in 2020. The peak Wilson’s phalarope count from
all sites combined was 339,715 birds in 2019 (3 sites), and 126,288 birds in 2020 (6 sites).
Inclusion of unidentified birds in Wilson’s phalarope peak counts resulted in high counts of
370,811 birds in 2019 and 236,434 birds in 2020. The peak red-necked phalarope count from all
sites combined was 154,581 birds during 2019 (3 sites), and 53,762 in 2020 (6 sites). Inclusion
of unidentified birds in red-necked phalarope peak counts resulted in high counts of 291,643
birds in 2019 and 123,697 birds in 2020. The three additional sites monitored in 2020 added ≤1%
of the combined totals for each species/unidentified peak count. Timing of both species was
similar to historic patterns, with peak numbers in mid-July for Wilson’s phalaropes and in midto
late-August for red-necked phalaropes. Numbers of both species at Great Salt Lake
outnumbered those at other sites by an order of magnitude in 2019 and 2020. There is a need for
continuing standardization of survey methods across sites, research on phalarope movements
among sites and residence times at sites, and attention toward the issue of interpretation of
unidentified phalarope counts. Continued monitoring will help us understand phalarope
population trends, migratory patterns and timing, and response to climate and environmental
factors, and will provide a valuable indicator of the health of saline lake ecosystems.

Keywords

birds

waterbirds

population

Pond Complex

Alviso

Eden Landing

Ravenswood

Breeding Waterbird Populations Have Declined in South San Francisco Bay: An Assessment Over Two Decades

ariela — Tue, 28 Sep 2021 17:03:30 +0000

Breeding Waterbird Populations Have Declined in South San Francisco Bay: An Assessment Over Two Decades ariela Tue, 09/28/2021 - 10:03

Document Category

Scientific Reports

Author(s)

Date

2021-09

Summary

In south San Francisco Bay, former salt ponds now managed as wildlife habitat support large populations of breeding waterbirds. In 2006, the South Bay Salt Pond Restoration Project began the process of converting 50% to 90% of these managed pond habitats into tidal marsh. We compared American Avocet (Recurvirostra americana) and Black-necked Stilt (Himantopus mexicanus) abundance in south San Francisco Bay before (2001) and after approximately 1,300 ha of managed ponds were breached to tidal action to begin tidal marsh restoration (2019). Over the 18-year period, American Avocet abundance declined 13.5% (2,765 in 2001 vs. 2,391 in 2019), and Black-necked Stilt abundance declined 30.0% (1,184 in 2001 vs. 828 in 2019). Forster’s Tern (Sterna forsteri) abundance was 2,675 birds in 2019. In 2019, managed ponds accounted for only 25.8% of suitable habitats, yet contained 53.9%, 38.6%, and 65.6% American Avocet, Black-necked Stilt, and Forster’s Tern observations, respectively. Conversely, tidal marsh and tidal mudflats accounted for 42.9% of suitable habitats, yet contained only 18.4%, 10.3%, and 19.8% of American Avocet, Black-necked Stilt, and Forster’s Tern observations, respectively. Using a separate nest-monitoring data set, we found that nest abundance in south San Francisco Bay declined for all three species from 2005–2019. Average annual nest abundance during 2017–2019 declined 53%, 71%, and 36%, for American Avocets, Back-necked Stilts, and Forster’s Terns, respectively, compared to 2005–2007. Loss of island nesting habitat as a result of tidal marsh conversion and an increasing population of predatory California Gulls (Larus californicus) are two potential causes of these declines. All three species established nesting colonies on newly constructed islands within remaining managed ponds; however, these new colonies did not make up for the steep declines observed at other historical nesting sites. For future wetland restoration, retaining more managed ponds that contain islands suitable for nesting may help to limit further declines in breeding waterbird populations.

Hartman, C. A, Ackerman, J. T, Schacter, C. R, Herzog, M. P, Tarjan, L. M, Wang, Y., et al. (2021). Breeding Waterbird Populations Have Declined in South San Francisco Bay: An Assessment Over Two Decades. San Francisco Estuary and Watershed Science, 19(3). http://dx.doi.org/10.15447/sfews.2021v19iss3art4 Retrieved from https://escholarship.org/uc/item/16n259mc

Keywords

Pond Complex

Alviso

Eden Landing

Ravenswood

Content available here

San Francisco Estuary and Watershed Science, Volume 19, Issue 3

Social attraction used to establish Caspian tern (Hydroprogne caspia) nesting colonies on modified islands at the Don Edwards San Francisco Bay National Wildlife Refuge, California—Final report

Biruk — Fri, 01 Nov 2019 19:11:45 +0000

Social attraction used to establish Caspian tern (Hydroprogne caspia) nesting colonies on modified islands at the Don Edwards San Francisco Bay National Wildlife Refuge, California—Final report Biruk Fri, 11/01/2019 - 12:11

Document Category

Scientific Reports

Author(s)

Date

2018

Summary

Executive Summary
To address the 2008/2010 and Supplemental 2014 National Oceanic and Atmospheric
Administration Fisheries Biological Opinion for operation of the Federal Columbia River Power
System, the U.S. Army Corps of Engineers (USACE) and the Bureau of Reclamation (Reclamation)
developed and began implementation of Caspian tern (Hydroprogne caspia) management plans. This
implementation includes redistribution of the Caspian terns in the Columbia River estuary and the mid-
Columbia River region to reduce predation on salmonids listed under the Endangered Species Act. Key
elements of the plans are (1) reduction of nesting habitat for Caspian terns in the Columbia River estuary
and the mid-Columbia River region, and (2) creation or modification of nesting habitat at alternative
sites within the Caspian tern breeding range. As part of this effort, USACE and Reclamation developed
Caspian tern nesting habitat at the U.S. Fish and Wildlife Service Don Edwards San Francisco Bay
National Wildlife Refuge (DENWR), California, prior to the 2015 nesting season. Furthermore, nesting
habitat for western snowy plovers (Charadrius alexandrinus nivosus) also was developed to provide
separate nesting opportunities in the same managed ponds to reduce potential conflicts with Caspian
terns. Specifically, seven recently constructed islands within two managed ponds (Ponds A16 and SF2)
of DENWR were modified to provide habitat attractive to nesting Caspian terns (5 islands) and snowy
plovers (2 islands). These 7 islands were a subset of 46 islands recently constructed in Ponds A16 and
SF2 to provide waterbird nesting habitat as part of the South Bay Salt Pond (SBSP) Restoration Project.

We used social attraction methods (decoys and electronic call systems) to attract Caspian terns
and snowy plovers to these seven modified islands, and conducted surveys from March to September of
2015, 2016, and 2017 to evaluate nest numbers, nest density, and productivity. Results from the 2015
nesting season, the first year of the study, indicated that island modifications and social attraction
measures were successful in establishing Caspian tern breeding colonies at Ponds A16 and SF2 of
DENWR. Prior to 2015, there was no history of Caspian terns nesting in either Pond A16 or Pond SF2.
The success of 2015 continued in 2016 and 2017. In 2017, the third and final year of the project,
Caspian terns initiated at least 664 nests, fledged at least 239 chicks, and had a breeding success rate of
0.36 fledged chicks per breeding pair. This represents a 171 percent increase in the number of breeding
pairs and a 41 percent increase in the number of chicks fledged, but a 48 percent decrease in the
fledglings produced per breeding pair in 2017 compared to 2015, the first year the colonies were
established. The two new large and growing Caspian tern nesting colonies at Ponds A16 and SF2
demonstrate the effectiveness of social attraction measures in helping to establish tern nesting colonies
in San Francisco Bay. Social attraction measures similar to those used in this study, but targeting other
colonial species such as Forster’s terns (Sterna forsteri) and American avocets (Recurvirostra
americana), may help to establish waterbird breeding colonies at wetlands enhanced as part of the SBSP
Restoration Project.

Keywords

Pond Complex

Alviso

Ravenswood

Content available here

https://pubs.usgs.gov/of/2018/1136/ofr20181136.pdf