waterbirds

South Bay Salt Pond Waterbird Surveys, September 2021 – May 2022

ariela — Wed, 19 Feb 2025 19:40:41 +0000

South Bay Salt Pond Waterbird Surveys, September 2021 – May 2022 ariela Wed, 02/19/2025 - 11:40

Document Category

Scientific Reports

Author(s)

Gabbie Burns

SFBBO

Date

2022-10

Summary

FINAL REPORT

Suggested citation: Burns, G. 2022. South Bay Salt Pond Waterbird Surveys: September – May 2022. 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 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 (CDFW), 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 2021 and May 2022.

From September 2021 – May 2022, 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 also put these waterbird counts in the context of long-term trends to assess changes in waterbird numbers relative to baseline counts from before marsh restoration.

We recorded 1,248,069 waterbird observations of 78 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 6 out of 10 species/guilds has increased in SBSPRP ponds since prior to restoration activities in 2005 – 2007. Exceptions comprise phalaropes, Bonaparte’s gulls, dabbling ducks, medium shorebirds. Bonaparte’s gull counts declined by 84% which exceeds the threshold of a 50% decline in a single year.

As the SBSPRP progresses, we recommend a precautionary approach to waterbird management and tidal marsh restoration and maintenance of enough of the ponds within the project footprint to provide a variety of salinity and water levels suitable for many different guilds. Special consideration should be given to birds that traditionally prefer medium to high salinity ponds, such as phalaropes and Eared Grebes, since restoration activities have already reduced the prevalence of these habitat conditions and the remaining high salinity habitat is managed for salt production rather than waterbird needs. Creating or maintaining islands or undisturbed levees will provide additional nesting and roosting habitat for other guilds. As the restoration advances, continued monitoring of avian use of Cargill-managed and SBSPRP ponds will be valuable in assessing progress toward the management target of maintaining baseline waterbird numbers.

However, a regional perspective will be needed to tease apart drivers of waterbird use in the project area. With more than a decade of bird and water quality monitoring data available, a useful next step will be to model bird habitat use and to use the model to predict the impact of future restoration scenarios on bird abundance.

Keywords

Pond Complex

Alviso

Eden Landing

Ravenswood

South Bay Salt Pond Waterbird Surveys, September 2019 – February 2021

ariela — Wed, 19 Feb 2025 19:26:38 +0000

South Bay Salt Pond Waterbird Surveys, September 2019 – February 2021 ariela Wed, 02/19/2025 - 11:26

Document Category

Scientific Reports

Author(s)

Max Tarjan

Gabbie Burns

SFBBO

Date

2021-06

Summary

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 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 (CDFW), 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 2019 and February 2021.

From September 2019 to February 2020, we conducted waterbird surveys and water quality sampling at 82 ponds (22 Cargill-managed salt production ponds and 60 SBSPRP managed ponds). Due to site access limitations associated with the COVID-19 pandemic, we surveyed 45 ponds across multiple complexes from March to April 11, 2020 and 25 ponds within Eden Landing Ecological Reserve from April 15 to May 2020 and December 2020 to February 2021. 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 also put these waterbird counts in the context of long-term trends to assess changes in waterbird numbers relative to baseline counts from before marsh restoration. We recorded 1,293,322 waterbird observations of 78 species (all sites combined). The Alviso and Eden Landing pond complexes supported the greatest species diversity and also the highest abundances of all complexes. The abundances of diving ducks, Ruddy ducks, dabbling ducks, and medium shorebirds in winter, as well as small shorebirds in fall and Least Terns in summer have increased in SBSPRP ponds since prior to restoration activities in 2005–2007. Counts of small shorebirds in spring remain at baseline values. Eared Grebes have increased in active salt production ponds (Coyote Hills, Dumbarton, and Mowry complexes), but not in SBSPRP ponds (Alviso, Eden Landing, and Ravenswood complexes), and Bonaparte’s gulls have declined by 18%. Since limited ponds were surveyed in 2020, meaningful comparisons to previous years’ data were restricted to a subset of sites in spring and winter. Further, no fall surveys were completed in 2020. While the results presented in this report are informative, a complete understanding of contemporary waterbird trends in the project area will require resumption of surveys at all sites in fall, winter, and spring of 2021-2022.

Phalarope migration surveys in 2020 found that counts of Wilson’s phalaropes peaked at 767 phalaropes on July 21 and counts of Red-necked phalaropes peaked at 1,700 phalaropes on August 28. The peak count of Red-necked phalaropes was higher than in 2019 (1,447 phalaropes), despite visiting fewer ponds in 2020.

As the SBSPRP progresses, we recommend a precautionary approach to waterbird management and tidal marsh restoration and maintenance of enough of the ponds within the project footprint to provide a variety of salinity and water levels suitable for many different guilds. Special consideration should be given to birds that prefer medium to high salinity ponds, such as phalaropes and Eared Grebes, since restoration activities have already reduced the prevalence of these habitat conditions and the remaining high salinity habitat is managed for salt production rather than waterbird needs. Creating or maintaining islands or undisturbed levees will provide additional nesting and roosting habitat for other guilds. As the restoration advances, continued monitoring of avian use of Cargill-managed and SBSPRP ponds will be valuable in assessing progress toward the management target of maintaining baseline waterbird numbers. However, a regional perspective will be needed to tease apart drivers of waterbird use in the project area. With more than a decade of bird and water quality monitoring data available, a useful next step will be to model bird habitat use and to use the model to predict the impact of future restoration scenarios on bird abundance.

Keywords

Pond Complex

Alviso

Eden Landing

Ravenswood

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

Habitat Use by Breeding Waterbirds in Relation to Tidal Marsh Restoration in the San Francisco Bay Estuary

ariela — Tue, 27 Jun 2023 18:27:53 +0000

Habitat Use by Breeding Waterbirds in Relation to Tidal Marsh Restoration in the San Francisco Bay Estuary

Map of 2019 avocet observations

ariela Tue, 06/27/2023 - 11:27

Document Category

Scientific Reports

Author(s)

Date

2023-06

Summary

Abstract

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

Pond Complex

Alviso

Eden Landing

Ravenswood

Content available here

eScholarship link to paper

Monitoring Nesting Waterbirds for the South Bay Salt Pond Restoration Project: 2022 Breeding Season

admin — Wed, 05 Apr 2023 22:28:49 +0000

Monitoring Nesting Waterbirds for the South Bay Salt Pond Restoration Project: 2022 Breeding Season

Figure from: Ackerman, JT, CA Hartman, and MP Herzog. 2023. Monitoring nesting waterbirds for the South Bay Salt Pond Restoration Project: 2022 breeding season. U.S. Geological Survey Open-File Report

admin Wed, 04/05/2023 - 15:28

Document Category

Monitoring Reports

Author(s)

Joshua T. Ackerman

C. Alex Hartman

Mark P. Herzog

Date

2023-04-06

Summary

San Francisco Bay supports thousands of breeding waterbirds annually and historically has hosted large populations of American avocets (Recurvirostra americana), black-necked stilts (Himantopus mexicanus), and Forster’s terns (Sterna forsteri). These three species have relied largely on former agricultural salt ponds in South San Francisco Bay, which provide wetland foraging habitat as well as island nesting habitat. The South Bay Salt Pond Restoration Project is in the process of restoring up to 15,100 acres of these former salt ponds to tidal marsh and tidal mudflats. Although this restoration is expected to have numerous benefits including providing habitat for tidal wetland-dependent species, improved water quality, buffering against storm surge and protecting inland areas from sea level rise, the reduction in former salt pond habitat and nesting islands therein may negatively impact breeding waterbirds. To address this, the South Bay Salt Pond Restoration Project also includes enhancements to remaining pond habitat such as the construction of new islands for nesting. Moreover, the South Bay Salt Pond Restoration Project follows an adaptive management plan in which waterbird response to the changing landscape is monitored over time to ensure that existing breeding waterbird populations are maintained. In this report, we provide results of waterbird nest monitoring in South San Francisco Bay during the 2022 breeding season and present these results in the context of annual nest monitoring in South San Francisco Bay since 2005. Overall nest abundance remained at or near 18-year lows for American avocets (176 nests) and black-necked stilts (97 nests), but Forster’s tern nest abundance (1,727 nests) was at an 18-year high, reversing historically low abundance observed during 2015-2017. In 2022, there were only 6 American avocet, 3 blacknecked stilt, and 4 Forster’s tern major colony nesting sites, down from annual averages of 12.4, 6.6, and 6.6 observed during 2005-2009. Nest success (30% for American avocets, 29% for black-necked stilt, and 53% for Forster’s terns) was below 2005-2007 baseline values established for the South Bay Salt Pond Restoration Project. Average egg hatching success (98%, 100%, and 90%), and clutch sizes (3.68, 3.70, and 2.63 eggs) of American avocets, black-necked stilts, and Forster’s terns, respectively, were similar to values observed during 2005-2010. All three species exhibited notable shifts in nest initiation dates in 2022, with American avocets and Forster’s terns nesting 10-11 days earlier and black-necked stilts nesting 10 days later than during 2005-2010. Finally, the enhanced managed ponds with newly constructed islands (Ponds A16 and SF2) supported 86% of all the Forster’s tern nests recorded in South San Francisco Bay in 2022, the first time these managed ponds have hosted such a substantial number of tern nests.

Table 1: USGS has monitored nesting waterbird populations and their reproductive success in the South Bay Salt Pond Restoration Project area since 2005 (2005-2022). This table represents demographic rates and nesting habitat parameters for American avocets, black-necked stilts, and Forster’s terns in San Francisco Bay during 2022.
Species	Number of nests	Clutch size	Nest success	Egg hatching success	Nest initiation date	Vegetation height (cm) at the nest	Percent vegetation cover at the nest	Percent bare ground at the nest
American avocet	176	3.68 (3.56 - 3.85)	30% (17 - 44%)	98% (95 - 100%)	May 4 (April 9 - June 5)	6.5 (5.8 – 7.3)	41.7% (36.5 – 47.0%)	58.2% (53.2 – 63.2%)
Black-necked stilt	97	3.70 (3.55 - 3.85)	29% (13 - 46%)	100% (100 - 100%)	May 13 (May 1 - June 25)	12.0 (10.4 – 13.5)	77.0% (70.2 – 83.7%)	22.1% (15.7 – 28.6%)
Forster's tern	1727	2.63 (2.56 - 2.69)	53% (41 - 63%)	90% (86% - 93%)	May 20 (May 11 – June 10)	8.0 (7.5 – 8.4)	56.4% (52.8 – 59.9%)	44.1% (40.9 – 47.3%)

Keywords

Pond Complex

Alviso

Eden Landing

Ravenswood

South Bay Salt Pond Restoration Project: Annual Report 2013

ariela — Thu, 23 Jun 2022 20:06:07 +0000

South Bay Salt Pond Restoration Project: Annual Report 2013

2013 Annual Report cover

ariela Thu, 06/23/2022 - 13:06

Document Category

Progress Reports

Author(s)

SBSP Project Management Team

Date

03-2014

Summary

A yearly snapshot of Project milestones and assessment of progress toward meeting restoration, public access and flood management goals

Keywords

trail use/public access

Colonial Waterbird Nesting Summary for Don Edwards San Francisco Bay National Wildlife Refuge and Eden Landing Ecological Reserve, South San Francisco Bay 2005

Dave Halsing — Tue, 26 Apr 2022 18:56:47 +0000

Colonial Waterbird Nesting Summary for Don Edwards San Francisco Bay National Wildlife Refuge and Eden Landing Ecological Reserve, South San Francisco Bay 2005 Dave Halsing Tue, 04/26/2022 - 11:56

Document Category

Scientific Reports

Author(s)

Cheryl M. Strong

SFBBO

Date

2005-11

Summary

This report conveys the results of the 2005 nesting waterbird monitoring program, led by the San Francisco Bay Bird Observatory.

Keywords

waterbirds

waterbird abundance