Waterbird Nesting Ecology and Management in San Francisco Bay Josh Ackerman, Alex Hartman, Mark Herzog, and Sarah Peterson U.S. Geological Survey (October 11, 2017)
Outline Wetland Management for Nesting Waterbirds 1) Some nesting waterbird populations are declining 2) High use of islands as nesting habitat 3) Construction and management of island nesting habitat 4) Social attraction techniques to establish nesting colonies 5) Predatory gull populations are increasing and gulls depredate eggs and chicks
Outline Wetland Management for Nesting Waterbirds 1) Some nesting waterbird populations are declining 2) High use of islands as nesting habitat 3) Construction and management of island nesting habitat 4) Social attraction techniques to establish nesting colonies 5) Predatory gull populations are increasing and gulls depredate eggs and chicks
Nesting Distributions of Waterbirds in South Bay 2005-2017 N=18,024 nests
Declining Populations & Colony Numbers in SF Bay Number of Nests 1600 1200 800 400 500 400 300 200 100 1600 1200 800 400 Number of Nesting Colonies 30 20 10 0 15 10 5 0 20 15 10 5 0 American Avocet Black-necked Stilt Forster's Tern Year Year
Fewer Nests in Fewer Places
Outline Wetland Management for Nesting Waterbirds 1) Some nesting waterbird populations are declining 2) High use of islands as nesting habitat 3) Construction and management of island nesting habitat 4) Social attraction techniques to establish nesting colonies 5) Predatory gull populations are increasing and gulls depredate eggs and chicks
Nests Are On Islands In Managed Ponds 100% 94% 75% 50% 25% 0% Forster s Terns (N=9,410 nests) % of Nests 100% 75% 50% 25% 74% American Avocets (N=6,875 nests) 0% 100% Black-necked Stilts (N=1,691 nests) 75% 50% 25% 0% 24% Island Marsh Levee Peninsula Mudflat Salt Flat Nest Habitat
Outline Wetland Management for Nesting Waterbirds 1) Some nesting waterbird populations are declining 2) High use of islands as nesting habitat 3) Construction and management of island nesting habitat 4) Social attraction techniques to establish nesting colonies 5) Predatory gull populations are increasing and gulls depredate eggs and chicks
Pond SF2 30 islands in 2011 Pond A16 20 islands in 2013 This information is preliminary and is subject to revision. It is being provided to meet the need for timely best science. The information is provided on the condition that neither the U.S. Geological Survey nor the U.S. Government may be held liable for any damages resulting from the authorized or unauthorized use of the information. South Bay Salt Pond Restoration Project
Nesting Islands Constructed in Managed Ponds 200 Pond A16: 16 new & 4 old islands Pond SF2: 30 new & 0 old islands Number of Nests 150 100 50 0 25 20 15 10 5 0 250 200 150 100 50 Construction Construction Construction Construction Construction Construction American Avocet Black-necked Stilt Forster's Tern 0 Year
Constructing Island Nesting Habitat 1) How many islands to put in a wetland? 2) Location of island within wetland? 3) Size and shape of island? 4) Topography of island?
Number of Nesting Islands Within Wetlands # Nests in Pond 90 80 70 60 50 40 30 20 10 0 Construct Fewer Islands in Many Wetlands 0 5 10 15 20 25 30 # Islands in Pond Forster s Terns Avocets Stilts E2 A16 SF2 Hartman et al. 2016 Journal of Wildlife Management 80:1177-1188
Nesting Island Location Within Wetlands Nest Success on Island 100% 80% 60% 40% 20% Construct Islands Far from Levees Forster s Terns Avocets Stilts 0% 0 50 100 150 200 250 300 Island Distance to Levee (m) Hartman et al. 2016 Journal of Wildlife Management 80:1177-1188
Nesting Island Shape # Nests on Island 60 50 40 30 20 Construct Linear Islands Forster s Terns Avocets Stilts 10 0 1 2 3 4 5 ROUND Island Shape Index LINEAR SF2 A1 A2W A16 Hartman et al. 2016 Journal of Wildlife Management 80:1177-1188
Constructing Island Nesting Habitat 1) How many islands to put in a wetland? 2) Location of island within wetland? 3) Size and shape of island? 4) Topography of island?
Island Topography & Nest Site Selection Real-time kinetics (RTK) GPS (1cm accuracy) Topography of 30 nesting islands Locations of >1,600 nests on islands Avocet Tern
Nest Site Location on Islands (Avocets) Nests Aspect Slope Elevation GPS points Probability of Nesting 0.05 0.04 0.03 0.02 0.01 0.00 0 3 6 9 12 15 18 21 Slope (degrees) Probability of Nesting Probability of Nesting Probability of Nesting 0.04 0.03 0.02 0.01 0.00 0 3 6 9 12 15 Distance to Water (m) 0.04 0.03 0.02 0.01 0.00 0.0 0.3 0.6 0.9 1.2 1.5 Elevation (m) 0.05 0.04 0.03 0.02 0.01 0.00 0 20 40 60 80 100 120 140 160 180 Aspect (degrees [direction nest faces]) This information is preliminary and is subject to revision. It is being provided to meet the need for timely best science. The information is provided on the condition that neither the U.S. Geological Survey nor the U.S. Government may be held liable for any damages resulting from the authorized or unauthorized use of the information. Hartman et al. 2016 Journal of Wildlife Management 80:1267-1279
Outline Wetland Management for Nesting Waterbirds 1) Some nesting waterbird populations are declining 2) High use of islands as nesting habitat 3) Construction and management of island nesting habitat 4) Social attraction techniques to establish nesting colonies 5) Predatory gull populations are increasing and gulls depredate eggs and chicks
Caspian Tern Social Attraction Islands Pond SF2 Caspian tern islands Pond A16
Caspian Tern Social Attraction 5 islands (2 in Pond A16, 3 in Pond SF2) Enhanced substrate: 10,000 yards 3 of ⅜ pea-gravel 50-150 tern decoys on each island Sound system broadcasting colony sounds March-September
Caspian Tern Social Attraction Number of Caspian Terns 600 400 200 ADULTS NESTS CHICKS FLEDGED Peak <2014 2015 2016 2017 # adults 0 374 484 711 # nests 0 224 317 501 # chicks hatched 0 192 207 331 # chicks fledged 0 174 158 230 0 2015 2016 2017
Outline Wetland Management for Nesting Waterbirds 1) Some nesting waterbird populations are declining 2) High use of islands as nesting habitat 3) Construction and management of island nesting habitat 4) Social attraction techniques to establish nesting colonies 5) Predatory gull populations are increasing and gulls depredate eggs and chicks
California Gull Breeding Population Growth in San Francisco Bay 60,000 50,000 Gull Population Size 40,000 30,000 20,000 10,000 0 1980 1985 1990 1995 2000 2005 2010 2015 Year neither the U.S. Geological Survey nor the U.S. Government may be held liable for any damages resulting from the authorized or unauthorized use of the information. Burns, CE, JT Ackerman, N Washburn, J Bluso-Demers, C Robinson-Nilsen, and C Strong. 2018. Three decades of California gull population growth and ecological impacts in the San Francisco Bay Estuary. Studies of Western Birds in press.
Gull Breeding Population 2007=37,000 2008=47,000 10% 12% 18% 60% neither the U.S. Geological Survey nor the U.S. Government may be held liable for any damages resulting from the authorized or unauthorized use of the information.
Gull Diet in San Francisco Bay (based on stable isotope analysis) 100% 80% Landfill foraging strategy Estuarine foraging strategy % of Gull Diet 60% 40% 20% 0% Individual gulls will specialize on prey; 1 gull killed 11 tern chicks Gull Diet Items neither the U.S. Geological Survey nor the U.S. Government may be held liable for any damages resulting from the authorized or unauthorized use of the information. Peterson et al. 2017 Ecological Indicators 74:205-215
Gull Predation on Waterbird Eggs and Chicks Eggs 11% of depredation on avocet & stilt Chicks 55% of avocet, 15% of stilt, 54% of tern chick deaths neither the U.S. Geological Survey nor the U.S. Government may be held liable for any damages resulting from the authorized or unauthorized use of the information. Ackerman et al. 2014 Journal of Wildlife Management 78:818-829 Ackerman et al. 2014 Journal of Avian Biology 45:609-623 Herring et al. 2011 Southwestern Naturalist 56:35-43
900% Increase in Tern Chick Survival at Pond A7 after Gull Colony Relocation Tern Chick Fledging Success 60% 50% 40% 30% 20% 10% 0% Gull Relocation from A6 2010 2011 2010 2011 Pond A2W Pond A7 Tern Colony Location and Year A6=23,000 gulls in colony in 2010 Tidally Restored A6 A2W A7 neither the U.S. Geological Survey nor the U.S. Government may be held liable for any damages resulting from the authorized or unauthorized use of the information. Ackerman et al. 2014 Journal of Wildlife Management 78:818-829
Conclusions 1) Some nesting waterbird populations are declining 2) High use of islands as nesting habitat 3) Construction and management of island nesting habitat 4) Social attraction techniques to establish nesting colonies 5) Predatory gull populations are increasing and gulls depredate eggs and chicks neither the U.S. Geological Survey nor the U.S. Government may be held liable for any damages resulting from the authorized or unauthorized use of the information.
Support & Funding: South Bay Salt Pond Restoration Project Don Edwards San Francisco Bay National Wildlife Refuge Eden Landing Ecological Reserve Napa-Sonoma Marshes Wildlife Area U.S. Fish and Wildlife Service Ca. Dept. Fish and Wildlife San Francisco Bay Bird Observatory California Coastal Conservancy Resources Legacy Fund U.S. Army Corps of Engineers Santa Clara Valley Water District CALFED Ecosystem Restoration Program Photos by: Ken Phenicie, Michael Kern, Abe Borker, and Crystal Shore Contact jackerman@usgs.gov Acknowledgments neither the U.S. Geological Survey nor the U.S. Government may be held liable for any damages resulting from the authorized or unauthorized use of the information.