Coastal seabirds are prey generalists known to be influenced by food availability, oceanographic conditions, and predator disturbance. Elegant Terns (Thalasseus elegans) nest at three sites in southern California: south San Diego Bay, Bolsa Chica Ecological Reserve, and Los Angeles Harbor. Numbers of nesting pairs fluctuate dramatically within and among years at these sites. I tested the hypothesis that nest numbers were related to prey abundance, chlorophyll a, sea surface temperature (SST), or predator disturbance. Abundances of four of the tern’s key prey species—northern anchovy, Pacific sardine, jacksmelt and topsmelt—were obtained from data on fish entrapped in nearby power-plant intakes. Chlorophyll a and SST were measured by in-situ data from the California Cooperative Oceanic Fisheries Investigations program and satellite data from the MODIS sensor aboard the Terra satellite. Nest number was not related to prey abundance, chlorophyll a or SST according to bootstrap regression analyses. Predator disturbance was estimated by the number of Peregrine Falcon, feral dog and coyote observations at the San Diego site, which had the most detailed data. Disturbance was higher during courtship in crash years (<825 nests) than non-crash years (mean = 8, SD = ±3.96, N = 6, median = 7.5; and mean = 3.44, SD = ±2.40, N = 9, median = 3, respectively). My results suggest that the courtship stage is a trial period in which Elegant Terns assess a site for suitability, in particular by the level of predator disturbance. However, we need standardized methods of collecting disturbance data and nest numbers to generalize findings across all Elegant Tern colonies in southern California.
|Advisor:||Horn, Michael H.|
|Commitee:||Abraham, Joel K., Behseta, Sam, Wu, Jindong|
|School:||California State University, Fullerton|
|School Location:||United States -- California|
|Source:||MAI 55/04M(E), Masters Abstracts International|
|Keywords:||Breeding ecology, Oceanography, Predator disturbance, Prey availability, Seabird, Southern California Bight, Thalasseus elegans|
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