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Responses of California Brown Pelicans to disturbances at a large Oregon roost

Waterbirds

By:
, , and
DOI: 10.1675/1524-4695(2007)030[0479:ROCBPT]2.0.CO;2

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Abstract

Numbers of California Brown Pelicans (Pelecanus occidentalis californicus) along the coast of Oregon and Washington have increased sharply in recent years. We identified East Sand Island in the Columbia River estuary as the site of the largest pelican roost within this region. Numbers of pelicans roosting on East Sand Island have increased from less than 100 during 1979-1986 to a high count of 10,852 in 2002. The East Sand Island roost is currently the site of a major non-breeding aggregation of this endangered subspecies. Total numbers of pelicans roosting on East Sand Island increased seasonally from April to September or October, and then declined sharply with the onset of winter storms. Pelicans appeared to forage more during low tides, and return to the roost during high tides; therefore, pelican numbers on the island were positively associated with tide height. Land-based human disturbance was negatively associated with total pelican numbers, whereas water-based human disturbance had no significant effect on total pelican numbers on the island. Natural disturbances, although more frequent than human disturbances, apparently did not influence the total number of pelicans on the island.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Responses of California Brown Pelicans to disturbances at a large Oregon roost
Series title:
Waterbirds
DOI:
10.1675/1524-4695(2007)030[0479:ROCBPT]2.0.CO;2
Volume
30
Issue:
4
Year Published:
2007
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Waterbirds
First page:
479
Last page:
487
Number of Pages:
9