Oregon State University Real Time Research, Inc. USGS-Oregon Cooperative Fish & Wildlife Research Unit Pre-Management Status of Caspian Tern Colonies in the Columbia Plateau Region: Foraging Behavior, Connectivity, and Reliance on Juvenile Salmonids 2013 Research Results

Acknowledgments Co-authors: Ken Collis (Co-PI), Allen Evans, Don Lyons, Pete Loschl, Yasuko Suzuki, Kirsten Bixler, Brad Cramer, Mike Hawbecker, Jessica Adkins, and Tim Lawes Collaborators: U.S. Bureau of Reclamation NOAA Fisheries Oregon Department of Fish and Wildlife Washington Department of Fish and Wildlife U.S. Fish & Wildlife Service Pacific States Marine Fisheries Commission Funding: Grant County Public Utility District (Curt Dotson) U.S. Army Corps of Engineers, Walla Walla District (David Trachtenbarg & Chris Pinney) Bonneville Power Administration (John Skidmore & Dave Roberts)

Crescent Island Tern Colony, McNary Pool Island created from dredge spoil in 1985 Island created from dredge spoil in 1985 Much larger California Gull colony shares the island Much larger California Gull colony shares the island

Goose Island Tern Colony, Potholes Reservoir Rock Island Dam Wanapum Dam Priest Rapids Dam Island created by reservoir Much larger gull colony shares the island

2013 Columbia River Plateau Caspian Tern Colony Sizes Arrows indicate change from 2012

2013 Columbia River Plateau Caspian Tern Productivity Arrows indicate change from 2012

Blalock Islands, John Day Pool Caspian Tern breeding colony

Re-sighting of Banded Caspian Terns

Estimated Caspian Tern Movements in 2013 Sand Island East Sand Island Goose Island Crescent Island Sand Island East Sand Island Goose Island Crescent Island Number of terns moved to Crescent Island Number of terns moved to Goose Island

Foraging Behavior

Caspian Tern Foraging Behavior at Goose Island, GPS tags deployed on May 20 th ; data retrieved from 23 birds 118 foraging trips tracked over 65 bird-days Largest foraging range by a breeding Caspian Tern ever documented:  93 km to Lyons Ferry Hatchery area on Snake River Foraging Trip Locations# Terns Only in/around Potholes Reservoir8 In/around Potholes + Columbia River8 All trips to Columbia River3 In/around Potholes + Snake River1 All trips to Snake River3

Example Trips to In/Around Potholes Reservoir

Example Trips to Columbia River

Example Trips to Snake River

Predation Rates on Salmonid Smolts

Predation Rate Methods

Predation on ESA-listed Salmonids by Caspian Terns at Goose and Crescent Islands, 2013 Predation Rates (95% C.I.) Salmonid ESU/DPSCrescent CATEGoose CATE UCR Steelhead2.8% ( )14.9% ( ) SR Steelhead2.8% ( )0.1% ( ) UCR Spr Chinook0.2% ( )1.7% ( ) SR Spr/Su Chinook0.5% ( )< 0.1% SR Fall Chinook0.6% ( )< 0.1% SR Sockeye0.5% ( )< 0.1% UCR predation rates based on fish last detected passing Rock Island Dam SR predation rates based on fish last detected passing Lower Monumental Dam

Caspian Tern Predation on Spring Chinook at Goose Island Relative to Run-timing, 2013

Caspian Tern Predation on Steelhead at Goose Island Relative to Run-timing, 2013

Summary of Key Findings in 2013 Caspian tern colonies at Crescent Island & Goose Island smaller in 2013 than in recent years, but experienced higher nesting success Considerable movement by Caspian terns from the large, managed colony in the Columbia River estuary to the Crescent Island & Goose Island colonies, and between those two largest colonies for the Columbia Plateau region Some Caspian terns nesting at Goose Island traveled up to 93 km to forage in the Columbia and Snake rivers Predation rates on UCR Spring Chinook were much less than on UCR Steelhead for Caspian terns from both Goose Island & Crescent Island colonies Despite apparent high fish production in Potholes Reservoir in 2013, predation rates on steelhead remained high, indicating a strong preference for river foraging

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Rock Island Dam: Sampling Summary Steelhead (n = 5,893) and Spring Chinook (n = 5,759) sampled from 10 April to 15 June, 2013 Random selection, with fish tagged in proportion to their relative abundance in-river Data recorded on fish origin (hatchery, wild), length, and external condition (body injuries, de-scaling, and other anomalies) Fish released directly into the tailrace of Rock Island Dam Estimated survival from Rock Island to McNary Dam was 62% and 77% for Steelhead and Spring Chinook, respectively

Caspian Tern Predation on Hatchery and Wild Salmonids at Goose Island, 2013 Predation Rate

Salmonids in the Diet of Caspian Terns Nesting on Goose Island,

2013 Diet Composition: Preliminary hypothesis for low proportion of salmonids Anecdotal reports of best fish production in Potholes Reservoir in years* Abundant local fish production may have changed bill-load deliveries to island - Terns may have readily caught fish close to colony for delivery to mates and chicks, rather than carry fish back from Columbia River Per capita steelhead predation rates based on PIT tag recoveries did not decline in 2013 Apparently high local prey abundance did not preclude long-distance foraging trips to Columbia and Snake rivers * Need to verify anecdotal reports of high fish production in Potholes Reservoir

Adult terns (banded as adults or banded as chicks & now ≥ 5 years old) -4 of 11 terns banded at East Sand Island were confirmed breeding at Crescent Island Color-banded Caspian Tern movements to Crescent Island & Goose Island colonies in 2013 Sand Island East Sand Island Goose Island Crescent Island Sand Island East Sand Island Goose Island Crescent Island of 14 terns banded at East Sand Island were confirmed breeding at Goose Island

Example Trips to Wasteway Areas West of Potholes Reservoir On Return from Columbia River Local Trip Tagged terns often used the wasteway region where WDFW stocked ponds No conclusive evidence that the tagged terns used the WDFW ponds specifically, but Caspian terns were seen foraging there x

Use of Evergreen Reservoir Area x

2013 Columbia River Plateau Double-crested Cormorant Colony Sizes Arrows indicate change from 2012