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Seabird population trends along the west coast of North America: causes and the extent of regional concordance

Studies in Avian Biology

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Abstract

We compared trends in breeding population size among cormorants, gulls, alcids, and others, among the Farallon Islands, and sites in northern California and Washington, Gulf of Alaska, and Bering Sea, but in most cases only during the last two decades. For a given species, trends were usually concordant within the same oceanographic domain, except for Rhinoceros Auklet, which increased across all domains in its northeastern Pacific range. Overall, humans and their domestic animals have had severe negative impacts to individual islands, but recent restoration efforts have had spectacular results. On the other hand, the California Current and the eastern Bering Sea now seem unable to support historic populations of natural, top-trophic predators. The major factor responsible appears to be overfishing by humans of important seabird prey, especially, in a period when climate has been unstable. Notable trends indicating these general patterns were as follows: 1) The Ashy Storm-Petrel on the Farallon Islands, where 80% of this species breeds, may have decreased in response to the increase of gulls in the storm-petrel breeding habitat. 2) Brandt's and Pelagic cormorants in the central California Current declined radically owing to El Nino and antropogenic factors in the early 1980s, and have since failed to recover, contrary to trends in the 1970s; farther north, populations fluctuated slightly but at low levels during this period. 3) Large Larus gulls have increased. 4) Common Murres in the central and northern portions of the California Current exhibited a marked decline during the early 1980s and have since failed to recover. 5) Most Common Murre populations in the Gulf of Alaska appear to be stable; whereas those in the eastern Bering Sea are decreasing. 6) Rhinoceros Auklet has increased throughout its range and has (re-)colonized new sites in the southern portion of it. 7) Tufted Puffin has ceased recovery in the California Current, but in Alaska it has continued to recover from former anthropogenic impacts. 8) Cassin's Auklet has declined in the central California Current region.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Seabird population trends along the west coast of North America: causes and the extent of regional concordance
Series title:
Studies in Avian Biology
Volume
15
Year Published:
1994
Language:
English
Contributing office(s):
Alaska Biological Science Center
Description:
pp. 119-133
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Studies in Avian Biology
First page:
119
Last page:
133
Number of Pages:
15