Sex ratios of Dunlin wintering at two latitudes on the Pacific coast

Citation
Pcf. Shepherd et al., Sex ratios of Dunlin wintering at two latitudes on the Pacific coast, CONDOR, 103(2), 2001, pp. 352-360
Citations number
37
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Animal Sciences
Journal title
CONDOR
ISSN journal
0010-5422 → ACNP
Volume
103
Issue
2
Year of publication
2001
Pages
352 - 360
Database
ISI
SICI code
0010-5422(200105)103:2<352:SRODWA>2.0.ZU;2-Q
Abstract
Latitudinal dines in sex ratio during the nonbreeding season occur in some shorebirds of the Scolopacidae. We compared populations of nonbreeding Dunl in (Calidris alpina pacifica) from two latitudes along the Pacific flyway: the Fraser River Delta, British Columbia, and Bolinas Lagoon, California, t o determine whether, and to what degree, they exhibited sex ratios consiste nt with a latitudinal cline. Dunlin are plumage monomorphic, so we used a m aximum likelihood model to estimate overall and monthly sex ratios for each population based on culmen length distributions. Sex ratios in the Fraser River Delta were corrected for sex differences in habitat use. Monthly sex ratios were similar at the two sites but varied throughout the winter, like ly reflecting differences in seasonal movement patterns between the sexes. Both populations showed an overall bias toward males (Fraser = 61% males, B olinas = 65% males). Since there is no evidence to support the possibility of a skew toward males in C. a. pacifica as a whole, our data are consisten t with some form of latitudinal dine in the sex ratio of C. a. pacifica. Ho wever, additional data from the Oregon coast, southern California, and Mexi co are required to resolve this question. We also tested the hypothesis tha t mean body size within each sex is larger at the higher-latitude site (Fra ser River Delta), but this did nor appear to be the case.