Date

2008

Document Type

Master's Thesis

Degree Name

Master of Science (M.S.)

Department

Moss Landing Marine Laboratories

Abstract

Seabirds present an interesting challenge for quantifying and understanding dispersal because they are highly mobile but often exhibit natal site fidelity when breeding (Frederiksen and Petersen 2000, Steiner and Gaston 2005, Milot et al. 2008). I quantified movement and examined dispersal patterns of an elusive and threatened seabird, the Marbled Murrelet (Brachyramphus marmoratus) with genetic population assignments using thirteen microsatellite loci. Two genetically distinct populations of Marbled Murrelets were identified: one included birds from southern Alaska to northern California and the other included birds from central California. Pair-wise comparisons of Fst values for central California had the greatest genetic differentiation (0.034 ± 0.001), whereas all other pair-wise comparisons had low Fst values (0.005 ± 0.001). I identified twenty-nine migrant birds from the northern populations in central California. A greater proportion of migrants was observed in central California during winter (November to March) than during breeding (April to July) and post-breeding (August to October) seasons. The number of female migrants (n = 18) was significantly greater than the number of male migrants (n = 9), implying that dispersal in Marbled Murrelets was sex-biased. In addition, migrant birds had shorter residence times in central California than birds that were classified as residents, and a low proportion of migrants (0.02) had a first-order relative in central California. My results indicated that birds from the northern populations dispersed into central California but did not permanently recruit to the central California population. These migrants would increase competition with resident birds for resources without contributing to the reproductive output of the central California population and would be counted and included in population estimates potentially obscuring the detection of a population decline in the central California Marbled Murrelet population.

Comments

Thesis (M.S.) Division of Science and Environmental Policy. Moss Landing Marine Laboratories

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