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 ReclamationNOAA Fisheries Oregon Department of Fish and Wildlife Washington Department of Fish and WildlifeU.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 • 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 reservoirMuch larger gull colony shares the island

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Caspian Tern Colony Sizes

Arrows indicate change from 2012

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2013 Columbia River PlateauCaspian 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

East Sand Island

Goose Island

Crescent Island

56

92 East Sand Island

Goose Island

Crescent Island

2357

Number of terns moved to Crescent Island

Number of terns moved to Goose Island

Foraging Behavior

Caspian Tern Foraging Behavior at Goose Island, 2013

• 28 GPS tags deployed on May 20th; 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 Reservoir 8

In/around Potholes + Columbia River 8

All trips to Columbia River 3

In/around Potholes + Snake River 1

All trips to Snake River 3

Example Trips to In/Around Potholes Reservoir

Example Trips to Columbia River

Example Trips to Snake River

Predation Rates on Salmonid Smolts

Predation Rate Methods1 2

3 4

Predation on ESA-listed Salmonids byCaspian Terns at Goose and Crescent Islands, 2013

Predation Rates (95% C.I.)Salmonid ESU/DPS Crescent CATE Goose CATEUCR Steelhead 2.8% (2.2-3.5) 14.9% (12.8 - 17.8)

SR Steelhead 2.8% (2.4-3.4) 0.1% (0.1-0.2)

UCR Spr Chinook 0.2% (0.1-0.6) 1.7% (1.1 - 2.4)

SR Spr/Su Chinook 0.5% (0.4-0.7) < 0.1%

SR Fall Chinook 0.6% (0.4-0.9) < 0.1%

SR Sockeye 0.5% (0.1-1.0) < 0.1%

UCR predation rates based on fish last detected passing Rock Island DamSR predation rates based on fish last detected passing Lower Monumental Dam

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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

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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

Thanks! Questions?

Backup Slides

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

Hatchery Chinook

(n= 5,482)

Wild Chinook (n=277)

Hatchery steelhead

(n= 4,284)

Wild steelhead

(n= 1,609)

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Salmonids in the Diet of Caspian TernsNesting on Goose Island, 2010-2013

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April 10 -April 23

April 24 -May 7

May 8 -May 21

May 22 -June 4

June 5 -June 18

June 19 -July 2

July 3 -July 16

July 17 -July 30

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2010201120122013

2013 Diet Composition:Preliminary hypothesisfor 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

East Sand Island

Goose Island

Crescent Island

11

17

206

East Sand Island

Goose Island

Crescent Island

14131

39

- 6 of 14 terns banded at East Sand Island were confirmed breeding at Goose Island

Example Trips to Wasteway AreasWest 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

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Use of Evergreen Reservoir Area

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Double-crested Cormorant Colony Sizes

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