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Estuarine intertidal habitat use by birds in a Pacific Northwest coastal estuary
Citation:
LAMBERSON, J. O., M. Frazier, W. G. NELSON, AND H. LEE, II. Estuarine intertidal habitat use by birds in a Pacific Northwest coastal estuary. Presented at Pacific Estuarine Research Society annual meeting, Bellingham, WA, April 02 - 05, 2009.
Impact/Purpose:
Results of a year long study of the distribution of birds across five intertidal estuarine habitats reveal that tide level largely controls use of the habitats by birds.
Description:
Results of a year long study of the distribution of birds across five intertidal estuarine habitats reveal that tide level largely controls use of the habitats by birds. A total census of all birds observed from shoreline observation locations was made at five tide levels over six 2-month count cycles from December 2007 through December 2008. A total of 54,693 birds of 92 species assigned to eleven species groups were observed foraging, resting or hunting in intertidal habitats in Yaquina Estuary, Oregon. Gulls comprised 45% of all birds observed, and these along with ducks, shorebirds, corvids and geese comprised over 90%. The remaining 10% were herons/egrets, diving birds, rails (coots), passerines, raptors and alcids. In terms of total number of birds and population density the overall most important habitats supporting bird use were mudflat (frequently colonized by the burrowing mud shrimp Upogebia pugettensis) and Zostera marina eelgrass beds, followed by low marsh, sand flat (colonized by the burrowing mud shrimp Neotrypaea californiensis) and Zostera japonica. Taxonomic diversity was highest in sandflat, Z. marina, low marsh and mudflat, and lowest in Z. japonica. Bird distribution within the estuary was not uniform, with many more birds but fewer species in the lower embayments than upriver, and seasonality significantly affected population size and diversity. These data contribute to an understanding of ecosystem services provided by these intertidal habitats to birds, and by extension to all species, including humans, and to an analysis of the economic value of those habitats.