Cheryl M. Strong

Western Snowy Plover Numbers, Nesting Success, Fledging Success and Avian Predator Surveys in the San Francisco Bay, 2009

admin — Tue, 14 Nov 2023 21:33:41 +0000

Western Snowy Plover Numbers, Nesting Success, Fledging Success and Avian Predator Surveys in the San Francisco Bay, 2009 admin Tue, 11/14/2023 - 13:33

Document Category

Monitoring Reports

Author(s)

Caitlin W. Robinson-Nilsen

Cheryl M. Strong

Date

2009-11-18

Summary

The San Francisco Bay Bird Observatory (SFBBO), Don Edwards San Francisco Bay National Wildlife Refuge (Refuge), California Department of Fish and Game (CDFG), Hayward Area Recreational and Park District (HARD), and East Bay Regional Parks District (EBRPD) form the Western Snowy Plover Recovery Unit 3. The goal of this
collaboration is to survey former salt ponds and other habitats for Western Snowy Plovers (Charadrius alexandrinus nivosus), determine nest success of Snowy Plover nests and contribute to the management of the San Francisco Bay’s population of breeding Snowy Plovers. In 2009, we recorded Snowy Plover numbers, site use, nest success, fledging success, use of habitat enhancement projects, nest predators and avian predator numbers throughout the Snowy Plover breeding season.

During the 2009 breeding season window survey of the Pacific coast (24 May– 7 June) we counted 147 adult Snowy Plovers in the Bay. In 2009, we determined the fate 163 Snowy Plover nests in the South San Francisco Bay (South Bay). Ninety-six of the nests hatched (59%), 51 were depredated (31%), six were abandoned (3.6%), four were flooded (2.5%), three had unknown fates (1.8%) and two were lost at hatch (1.2%).

On Refuge property, we determined the fate of seven nests in the Alviso salt pond complex (pond A8, the Alviso impoundment and the dry pan area of New Chicago Marsh), 33 nests in the Ravenswood complex (ponds RSF2 and R1 – R5) and 21 nests in the Warm Springs complex (ponds A22 and A23). Out of these nests, 42 hatched (68.8%), 17 were depredated (27.8%), 1 was abandoned (1.6%) and 1 had an unknown fate (1.6%).

This year we determined the fate of 97 Snowy Plover nests at Eden Landing Ecological Reserve. Of the 97 nests, 53 hatched (55%), 32 were depredated (33%), 2 were lost at hatching (2%), 4 were flooded (4%), 5 were abandoned (5%) and 1 had an unknown fate (1%).

We determined the fate of five nests at Hayward Shoreline, one nest in the Old Oliver Brothers North salt ponds, which was depredated, and four nests on EBRPD’s Least Tern island. Out of these four nests, one was depredated by a Killdeer (Charadrius vociferous), two nests were found with broken eggs and one hatched.

Throughout the South Bay, we banded 113 chicks this breeding season. From visual observations, we determined that 28 chicks survived to fledging (24.8%) as of 30 September 2009. Using only the data where all the chicks in the brood were banded (n=29), the number of chicks fledged per male was 0.62.

During avian predator surveys we counted California Gulls (Larus californicus) and unidentified gulls as the most numerous avian predators in all areas surveyed.

SFBBO and the Refuge began a Snowy Plover habitat enhancement study beginning the winter of 2008 at Eden Landing Ecological Reserve. Enhancements consisted of oyster shells spread by hand at densities of five to eight shells/m² over seven one ha plots. More Snowy Plovers nested in shell plots than in control plots, and nests in shell plots were more likely to hatch than all other nests not in shell plots. The highest nest density we recorded was six active nests in a one ha shell plot.

SFBBO, with the help of H.T. Harvey and Associates, deployed camera systems at Snowy Plover nests at Eden Landing. Camera systems were placed at 24 nests and recorded footage 24 hours a day. We recorded eight depredation events on film, including two separate events where California Gulls depredated a Snowy Plover nest and chicks. The camera systems also recorded Common Ravens (Corvus corax), Northern Harriers (Circus cyaneus) and Red-tailed Hawks (Buteo jamaicensis) depredating Snowy Plover nests.

The South Bay Salt Pond Restoration Project, which encompasses much of the South Bay, should continue to consider the habitat requirements of Western Snowy Plovers in the restoration planning process, including the need for large expanses of dry salt pond nesting substrate adjacent to foraging areas.

Pond Complex

Alviso

Eden Landing

Ravenswood

Content available here

Western Snowy Plover Monitoring, 2009

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

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

Pond Complex

Alviso

Eden Landing

Ravenswood

Colonial Waterbird Nesting Summary for the South San Francisco Bay, 2006

Dave Halsing — Tue, 26 Apr 2022 18:54:54 +0000

Colonial Waterbird Nesting Summary for the South San Francisco Bay, 2006 Dave Halsing Tue, 04/26/2022 - 11:54

Document Category

Scientific Reports

Author(s)

Cheryl M. Strong

SFBBO

Date

2006-11

Summary

This report conveys the results of the 2006 nesting waterbird monitoring program, led by the San Francisco Bay Bird Observatory.

Keywords

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

Establishing Forster’s Tern (Sterna forsteri) Nesting Sites at Pond A16 Using Social Attraction for the South Bay Salt Pond Restoration Project

ariela — Mon, 10 Aug 2020 18:52:54 +0000

Establishing Forster’s Tern (Sterna forsteri) Nesting Sites at Pond A16 Using Social Attraction for the South Bay Salt Pond Restoration Project

Cover of Forster's tern report

ariela Mon, 08/10/2020 - 11:52

Document Category

Scientific Reports

Author(s)

Date

2020-07

Summary

Abstract

Forster’s terns (Sterna forsteri), historically one of the most numerous colonial-breeding waterbirds in South San Francisco Bay, California, have experienced recent decreases in the number of nesting colonies and overall breeding population size. The South Bay Salt Pond Restoration Project aims to restore 50–90 percent of former salt evaporation ponds to tidal marsh habitat in South San Francisco Bay. During phase 1 of the South Bay Salt Pond Restoration Project, the breaching of several pond levees to begin the process of tidal marsh restoration inundated island nesting habitat that had been used by Forster’s terns, American avocets (Recurvirostra americana), and other waterbirds. Additional nesting habitat could be lost as more managed ponds are converted to tidal marsh in the future. To address this issue, the South Bay Salt Pond Restoration Project organized the construction of new nesting islands in managed ponds that will not be restored to tidal marsh, thereby providing enduring island nesting habitat for waterbirds. In 2012, 16 new islands were constructed in Pond A16 in the Alviso complex of the Don Edwards San Francisco Bay National Wildlife Refuge, which increased the number of islands in this pond from 4 to 20. However, despite a long history of nesting on the four islands in Pond A16 before the 2012 construction activities, no Forster’s terns have nested in Pond A16 during the 7-year period (2012–18) after island construction.

During the 2017 and 2019 breeding seasons, we used social attraction measures (decoys and colony call playback systems) to attract Forster’s terns to islands within Pond A16 to re-establish nesting colonies. We maintained these systems from March through August in each year. To evaluate the effect of these social attraction measures, we completed surveys (between April and August) where we recorded the number and location of all Forster’s terns and other waterbirds using Pond A16, and we monitored waterbird nests. We compared bird survey and nest monitoring data collected in 2017 and 2019 to data collected in 2015 and 2016, prior to the implementation of social attraction measures, allowing for direct evaluation of the effect of social attraction efforts on Forster’s terns.

To increase the visibility and stakeholder involvement of this project, we engaged in multiple outreach activities in 2017, 2019, and 2020, including the development of a project website and educational video; publication of popular articles in 2017 and 2020; the development of outreach materials describing the project to the general public; and public presentations to relay findings to managers, stakeholders, and the general public.

The relative abundance of Forster’s terns in Pond A16, after adjusting for the overall South San Francisco Bay breeding population each year, was higher during the nesting period in 2017 and 2019 (when social attraction was used) than in 2015 and 2016 (before social attraction was used). Furthermore, more Forster’s terns were observed during the pre-nesting and nesting periods in the areas of Pond A16 where decoys and call systems were deployed. Although no Forster’s tern nests were observed in Pond A16 before social attraction was implemented (2015, 2016), or during the first-year social attraction was implemented (2017), 35 Forster’s tern nests were recorded during the second year of social attraction implementation in 2019. These 35 nests represent a re-establishment of a Forster’s tern nesting colony to Pond A16 for the first time in 8 years. As social attraction efforts often benefit from multiple years of decoy and call system deployment, results from 2017 and 2019 suggest that continued implementation of social attraction measures could help to ensure Forster’s tern breeding colonies persist in Pond A16 and other areas of South San Francisco Bay.

Suggested Citation

Hartman, C.A., Ackerman, J.T., Herzog, M.P., Wang, Y., and Strong, C., 2020, Establishing Forster’s Tern (Sterna forsteri) nesting sites at pond A16 using social attraction for the South Bay Salt Pond restoration project: U.S. Geological Survey Open-File Report 2020–1081, 28 p., https://doi.org/10.3133/ofr20201081.

ISSN: 2331-1258 (online)

Keywords

Pond Complex

Alviso

Evaluation of Caspian tern (Hydroprogne caspia) and snowy plover (Charadrius alexandrinus nivosus) nesting on modified islands at the Don Edwards San Francisco Bay National Wildlife Refuge, California—2015 Annual Report

Dave Halsing — Wed, 22 Jan 2020 21:19:20 +0000

Evaluation of Caspian tern (Hydroprogne caspia) and snowy plover (Charadrius alexandrinus nivosus) nesting on modified islands at the Don Edwards San Francisco Bay National Wildlife Refuge, California—2015 Annual Report Dave Halsing Wed, 01/22/2020 - 13:19

Document Category

Scientific Reports

Author(s)

Date

2016-03-24

Keywords

Pond Complex

Alviso

Ravenswood

Content available here

USGS Publications

Evaluation of Caspian tern (Hydroprogne caspia) and snowy plover (Charadrius alexandrinus nivosus) nesting on modified islands at the Don Edwards San Francisco Bay National Wildlife Refuge, California--2016 Annual report

Dave Halsing — Wed, 22 Jan 2020 21:11:36 +0000

Evaluation of Caspian tern (Hydroprogne caspia) and snowy plover (Charadrius alexandrinus nivosus) nesting on modified islands at the Don Edwards San Francisco Bay National Wildlife Refuge, California--2016 Annual report Dave Halsing Wed, 01/22/2020 - 13:11

Document Category

Scientific Reports

Author(s)

Date

2017-05-08

Keywords

Caspian tern

snowy plover

nesting islands

Pond Complex

Alviso

Ravenswood

Content available here

USGS Publications

Evaluation of social attraction measures to establish Forster's tern (Sterna forsteri) nesting colonies for the South Bay Salt Pond Restoration Project, San Francisco Bay, California--2017 Annual Report

Dave Halsing — Wed, 22 Jan 2020 21:05:37 +0000

Evaluation of social attraction measures to establish Forster's tern (Sterna forsteri) nesting colonies for the South Bay Salt Pond Restoration Project, San Francisco Bay, California--2017 Annual Report Dave Halsing Wed, 01/22/2020 - 13:05

Document Category

Scientific Reports

Author(s)

Date

2018-05-31

Keywords

Forster’s tern

social attraction

nesting density

Pond Complex

Alviso

Content available here

USGS Publications

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