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Intertidal estuarine habitat utilization by birds in a Pacific Northwest coastal estuary
Citation:
LAMBERSON, J. O., M. R. FRAZIER, W. G. NELSON, AND H. LEE, II. Intertidal estuarine habitat utilization by birds in a Pacific Northwest coastal estuary. Presented at Coastal and Estuarine Research Federation 20th Biennial Conference, Portland, OR, November 01 - 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 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 together with ducks, shorebirds, corvids and geese comprised over 90% of abundance. 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 were mudflat (frequently colonized by Upogebia pugettensis (mud shrimp)) and Zostera marina (eelgrass) beds, followed by low marsh, sand flat (colonized Neotrypaea californiensis (ghost shrimp)) and Zostera japonica. Taxonomic diversity was highest in sandflat, Z. marina, low marsh and mudflat, and lowest in Z. japonica habitats. Bird distribution within the estuary was not uniform, with many more birds but fewer species occurring in the lower embayments as compared with upriver. Seasonality significantly affected population size and diversity. More detailed observations in 2009 using the same methodology focused on the impact of Z. japonica on waterfowl, shorebirds and other species, as well as patterns of habitat use in other estuaries. These data contribute to an understanding of ecosystem services provided by these intertidal habitats to birds, and by extension to all species, including humans.