Age and sex of Common Murres Uria aalge recovered during the 1997-98 Point Reyes Tarball Incidents in central California

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Nevins, H. M., & Carter, H. R. (2003). Age and sex of Common Murres Uria aalge recovered during the 1997-98 Point Reyes Tarball Incidents in central California. Marine Ornithology, 31(1), 51-58.
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TitleAge and sex of Common Murres Uria aalge recovered during the 1997-98 Point Reyes Tarball Incidents in central California
AuthorsH. Nevins, H. Carter
AbstractWe examined 1,138 Common Murre Uria aalge carcasses recovered along the central California coast from November 1997 through March 1998 during the Point Reyes Tarball Incidents, a prolonged oiling event traced to the sunken vessel S. S. Jacob Luckenbach. We used head plumage, supraorbital ridge, and bursa of Fabricius, to classify age among carcasses as hatch-year (HY), or after-hatch year (AHY). We then separated AHY birds into two maturity categories based on gonad development: subadult and adult. The observed age class composition (14.6% HY, 37.6% subadult, and 47.8% adult) was not different from expected values generated with a stage-based matrix model that assumed a year-round resident population. The sex ratio for HY birds was equal (1.2:1 ), indicating little difference in at-sea distribution among male and female HY birds during winter. We found male-biased sex ratios in subadult (1.6:1) and adult (1.5:1) age classes. Sex-based differences in winter dispersal or colony attendance may have caused different risks to oiling among AHY birds. Mortality of mostly AHY murres during the Point Reyes Tarball Incidents and other oil spills has contributed to slow recovery of the central California population following historic and recent declines.
JournalMarine Ornithology
Date2003
Volume31
Issue1
Start page51
End page58
ISSN1018-3337
Subjectsage, mortality, oil pollution, seabird, sex ratio, California, North America, Point Reyes, United States, Aves, Laridae, Uria, Uria aalge
NoteCited By (since 1996):11, Marine Mammals, Birds & Turtles

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