Sexing California gulls using morphometrics and discriminant function analysis

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A discriminant function analysis (DFA) model was developed with DNA sex verification so that external morphology could be used to sex 203 adult California Gulls (Larus californicus) in San Francisco Bay (SFB). The best model was 97% accurate and included head-to-bill length, culmen depth at the gonys, and wing length. Using an iterative process, the model was simplified to a single measurement (head-to-bill length) that still assigned sex correctly 94% of the time. A previous California Gull sex determination model developed for a population in Wyoming was then assessed by fitting SFB California Gull measurement data to the Wyoming model; this new model failed to converge on the same measurements as those originally used by the Wyoming model. Results from the SFB discriminant function model were compared to the Wyoming model results (by using SFB data with the Wyoming model); the SFB model was 7% more accurate for SFB California gulls. The simplified DFA model (head-to-bill length only) provided highly accurate results (94%) and minimized the measurements and time required to accurately sex California Gulls.
Publication type Article
Publication Subtype Journal Article
Title Sexing California gulls using morphometrics and discriminant function analysis
Series title Waterbirds
DOI 10.1675/063.033.0109
Volume 33
Issue 1
Year Published 2010
Language English
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Waterbirds
First page 79
Last page 85
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