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Waterbird and mammal censuses at Siuslaw Estuary, Lane County, Oregon Public Deposited

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  • At the Siuslaw Estuary or some adjacent areas, U. S. Fish and Wildlife Service (USFWS) Biologists John Annear, John Cornely, and Roy Lowe conducted 67 censuses; Maureen Woolington made 90 censuses, and Range Bayer completed 429 censuses. Unfortunately, these censuses do not give a complete picture of the seasonality, abundance, and distribution for all waterbirds or mammals at Siuslaw Estuary because USFWS biologists mainly censused waterfowl, Bayer pooled all gulls and "peeps," only Bayer censused mammals, no one censused the entire Siuslaw Channel for all birds, and no one made many censuses in summer. Further, only Woolington sometimes censused nonwaterfowl in intertidal salt marshes. Nevertheless, there are sufficient censuses to greatly elucidate the status and distribution of many species. Highlights are given in the rest of this paragraph. Humans, especially those with hunting dogs, sometimes disrupted bird activity. Harbor seals regularly rested in the water or hauled out at two embayments in the lower Siuslaw Estuary during high tide. Brown Pelicans were uncommon. The Siuslaw region is a very important area along the Oregon Coast for wintering Tundra Swans, but their abundance sometimes changes from year to year. Great Basin Canada Geese (which were released here in 1983) now nest at the Siuslaw and appear to be permanent residents with some migrants sometimes swelling the population. Dabbling ducks and diving ducks were most abundant in January-March. Osprey and Bald Eagles were occasionally present in low numbers, but no Peregrine Falcons or Snowy Plovers were reported. American Coot numbers averaged less than 10/census. Yellowlegs and Whimbrels were only recorded during spring and fall migrations. Sanderlings were the most common "peep" in winter with as many as 260 recorded. Western Gull nesting was not apparent in the Estuary. Crows were abundant in intertidal areas in November-March, and Common Ravens were not numerous but were seen surprisingly often. Several birds normally considered as "terrestrial" were occasionally found on intertidal rocks, mudflats, or sandflats. It is also clear from these censuses that there can often be significant within-day (i.e., tidal), within-month, seasonal, and yearly variation in bird numbers. If possible, there should be several censuses each month under similar tidal conditions, so that the range in monthly variation can be determined. Unless monthly variation is measured each year, apparent differences in animal numbers between years may not represent real yearly variation in animal populations but may simply be artifacts of inadequate censusing. Unfortunately, it may not be feasible to do more than one census each month. But if the results are cautiously interpreted, one census/month is valuable and is certainly better than none. Because of the different censusing methods of Woolington, Bayer, and USFWS Biologists; it isn't possible to robustly compare their different study areas at the Siuslaw. However, a few comments about specific areas are in order. Many waterbird taxa (especially waterfowl) were more abundant east of the Highway 101 bridge at Florence than west of the bridge. The South Jetty Deflation Plain was the most important area at the Siuslaw for Tundra Swans. Site 8 (which is proposed to become a boat marina) was used by a greater variety of birds and usually more birds than the two adjacent, potential mitigation sites. Finally, Wendson Pasture received the heaviest use by Canada Geese and dabbling ducks of any area that was censused at the Siuslaw.
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  • Bayer, Range D. and Roy W. Lowe. 1988. Waterbird and mammal censuses at Siuslaw Estuary, Lane County, Oregon. Studies in Oregon Ornithology No. 4.
Table of Contents
  • Gahmken Press Purpose -- Title Page -- Copyright Page -- Abstract -- Bayer's Preface -- Lowe's Preface -- Acknowledgments -- Author's Division of Labor -- Table of Contents -- List of Tables -- List of Figures -- List of Appendices -- Chap. -- Appendices -- References -- Index
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