Cooperative Fish and Wildlife Research Units Program: Oregon
Education, Research and Technical Assistance for Managing Our Natural Resources

Oregon Project

Avian Predation on Juvenile Salmonids in the Lower Columbia River

February 1997 - January 2019

Personnel

Daniel Roby, Principal Investigator

Participating Agencies

DOE - Bonneville Power Administration

Long-term research, monitoring, and evaluation project investigating the impact of piscivorous colonial waterbirds on survival of ESA-listed salmonids from the Columbia River basin.

Research Publications

Research Publications	Publication Date
Lyons, D.E., and D.D. Roby. 2011. Validating growth and development of a seabird as an indicator of food availability: Captive-reared Caspian Tern chicks fed ad libitum and restricted diets. Journal of Field Ornithology 82: 88-100.	January 2011
Collis, K., D. D. Roby, D. P. Craig, S. Adamany, J. Y. Adkins, and D. E. Lyons. 2002. Colony size and diet composition of piscivorous waterbirds on the lower Columbia River: Implications for losses of juvenile salmonids to avian predation. Transactions of the American Fisheries Society 131: 537-550.	May 2002
Collis, K., D. D. Roby, D. P. Craig, B. A. Ryan, and R. D. Ledgerwood. 2001. Colonial waterbird predation on juvenile salmondis tagged with passive integrated transponders in the Columbia River estuary: vulnerability of different salmonid species, stocks, and rearing types. Transactions of the American Fisheries Society 130:385-396.	January 2001
Collar, S., D. D. Roby, and D. E. Lyons. Top-down and bottom-up interactions influence nesting success at the world's largest colony of Caspian terns (Hydroprogne caspia) in the Columbia River estuary. \| Abstract	April 2017	Our study investigated the influence of bottom-up and top-down drivers on the declining productivity at a once thriving breeding colony of Caspian terns (Hydroprogne caspia). Situated at the mouth of the Columbia River, Oregon, East Sand Island (ESI) is home to the largest Caspian tern breeding colony in the world. Since 2001 the decline in reproductive success of Caspian terns at ESI has been associated with a significant increase in average river discharge during May and June. The abundance of forage fish for terns in the estuary was inversely related to river discharge, which also apparently affected the reliance of tern nest predators on the tern colony as a food source, resulting in increased disturbance and decreased reproductive success at the tern colony. There was a significant increase in disturbance rates by bald eagles (Haliaeetus leucocephalus) during June for terns nesting at the ESI colony, and eagle disturbance rates were positively associated with May river discharge. We found a significant increase in kleptoparasitism rates of terns by glaucous-winged/western gulls (Larus glaucescens x L. occidentalis) since 2001, and a significant negative relationship between average annual rates of gull kleptoparasitism and Caspian tern nesting success at ESI. Although correlational, our results support the hypothesis that the decline in Caspian tern nesting success at this large estuarine colony was primarily driven by the interaction of bottom-up and top-down factors, influencing tern productivity through the food supply, and triggering potential predators to identify the tern breeding colony as an alternative source of prey.

Technical Publications

Technical Publications	Publication Date
Roby, D.D., K. Collis, D.E. Lyons, A. Evans, J.Y. Adkins, Y. Suzuki, P. Loschl, T. Lawes, K. Bixler, B. Cramer, A. Peck-Richardson, M. Hawbecker, N. Hostetter, E. Dykstra, J. Harms, W. Mashburn, J. Tennyson, N. Ventolini, R.D. Ledgerwood, and S. Sebring. 2012. Research, monitoring, and evaluation of avian predation on salmonid smolts in the lower and mid-Columbia River. Final 2011 Annual Report. Bonneville Power Administration and U.S. Army Corps of Engineers, Portland, OR. 171 pp.	August 2012

Theses and Dissertations

Theses and Dissertations	Publication Date
Wright, S.K. 2005. Disturbance and roosting ecology of California brown pelicans (Pelecanus occidentalis californicus) on East Sand Island in the Columbia River estuary. M.S. thesis, Oregon State University, Corvallis, OR. 106 pp.	June 2005
Suzuki, Y. 2012. Piscivorous colonial waterbirds in the Columbia River estuary: Demography, dietary contaminants, and management. Ph.D. dissertation, Oregon State University, Corvallis, OR. 204 pp.	January 2012
Myers, A.M. 2007. Evaluating the fatty acid signature technique for studies of diet composition in piscivorous waterbirds. M.S. thesis, Oregon State University, Corvallis, OR. 107 pp.	June 2007
Lyons, D.E. 2004. Foraging ecology of Caspian terns and double-crested cormorants in the Columbia River estuary. M.S. thesis, Oregon State University, Corvallis, OR. 90 pp.	June 2004
Collar, S. 2013. Site fidelity and colony dynamics of Caspian terns nesting at East Sand Island, Columbia River estuary, Oregon, USA. M.S. in Wildlife Science, Oregon State University, Corvallis, OR. 125 pp.	December 2013
Bailey, O.A. 2018. Extrinsic and intrinsic factors associated with reproductive success of Caspian Terns (Hydroprogne caspia) at East Sand Island, Columbia River estuary. M.S. thesis, Oregon State University, Corvallis, Oregon. 142 pp.	September 2018
Anderson, S.K. 2003. Foraging ecology, colony attendance, and chick provisioning of Caspian terns (Sterna caspia) in the Columbia River estuary. M.S. thesis, Oregon State University, Corvallis, OR. 101 pp.	December 2003