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Demographics of Piscivorous Colonial Waterbirds and Management Implications for ESA-listed Salmonids on the Columbia Plateau

ScholarsArchive at Oregon State University

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Title Demographics of Piscivorous Colonial Waterbirds and Management Implications for ESA-listed Salmonids on the Columbia Plateau
Names Adkins, Jessica Y. (creator)
Lyons, Donald E. (creator)
Loschl, Peter J. (creator)
Roby, Daniel D. (creator)
Collis, Ken (creator)
Evans, Allen F. (creator)
Hostetter, Nathan J. (creator)
Date Issued 2014-11 (iso8601)
Note To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by the Northwest Scientific Association and can be found at: http://www.bioone.org/loi/nwsc.
Abstract We investigated colony size, productivity, and limiting factors for five piscivorous waterbird species nesting at 18 locations
on the Columbia Plateau (Washington) during 2004–2010 with emphasis on species with a history of salmonid
(Oncorhynchus spp.) depredation. Numbers of nesting Caspian terns (Hydroprogne caspia) and double-crested cormorants
(Phalacrocorax auritus) were stable at about 700–1,000 breeding pairs at five colonies and about 1,200–1,500 breeding
pairs at four colonies, respectively. Numbers of American white pelicans (Pelecanus erythrorhynchos) increased at
Badger Island, the sole breeding colony for the species on the Columbia Plateau, from about 900 individuals in 2007 to
over 2,000 individuals in 2010. Overall numbers of breeding California gulls (Larus californicus) and ring-billed gulls (L.
delawarensis) declined during the study, mostly because of the abandonment of a large colony in the mid-Columbia River.
Three gull colonies below the confluence of the Snake and Columbia rivers increased substantially, however. Factors that
may limit colony size and productivity for piscivorous waterbirds nesting on the Columbia Plateau included availability
of suitable nesting habitat, interspecific competition for nest sites, predation, gull kleptoparasitism, food availability, and
human disturbance. Based on observed population trends alone, there is little reason to project increased impacts to juvenile
salmonid survival from tern and cormorant populations. Additional monitoring and evaluation may be warranted to
assess future impacts of the growing Badger Island American white pelican colony and those gull colonies located near
mainstem dams or associated with Caspian tern colonies where kleptoparasitism is common.
Genre Article
Topic Piscivorous waterbirds
Identifier Adkins, J. Y., Lyons, D. E., Loschl, P. J., Roby, D. D., Collis, K., Evans, A. F., & Hostetter, N. J. (2014). Demographics of Piscivorous Colonial Waterbirds and Management Implications for ESA-listed Salmonids on the Columbia Plateau. Northwest Science, 88(4), 344-359. doi:10.3955/046.088.0408

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