In order to test biometrics and plumage variability in bluethroats Luscinia svecica in central Iberia, 185 birds were captured in four areas (Sierra-Béjar, Sierra-Piedrahita, Sierra-Gredos and Sierra-Paramera). Older bluethroats were significantly larger than second calendar year birds in wing, tail, and total body lengths, but not in tarsus and bill lengths. A multivariate analysis of variance (MANOVA) and a principal component analysis (PCA) were used. Total body length only varied significantly between sampling areas: the birds from Sierra-Béjar were larger than those from Sierra-Gredos and Sierra-Paramera, but were similar to those of Sierra-Piedrahita. Birds with a white spot, a chestnut spot or no spot were found. Therefore, the question arises whether there are three subspecies (L. s. cyanecula, L. s. svecica and L. s. azuricollis), or three forms of a single subspecies (L. s. azuricollis). The percentage of birds with and without a throat spot was similar in the four sampled areas, and the percentage of birds with a spot significantly increased with age. These observations suggest that some plumage characters, such as the throat spot, should not be used as taxonomic characters, at least in the area where this study was conducted.
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