Le. Palomares et al., SEX-RELATED AND AGE-RELATED BIOMETRIC VARIATION OF BLACK-HEADED GULLSLARUS-RIDIBUNDUS IN WESTERN-EUROPEAN POPULATIONS, Bird study, 44, 1997, pp. 310-317
A multivariate discriminant analysis was performed with biometric data
from 583 Black-headed Gulls Larus ridibundus of known sex, either win
tering in central Spain or wintering and breeding in The Netherlands.
The discriminant function calculated from these birds was applied to 1
158 Black-headed Gulls trapped in Madrid; age, sex and temporal differ
ences in biometrics were analysed for those birds. All measurements ta
ken varied significantly between the sexes, but head-and-bill length a
nd bill depth were the best discriminant variables. Bone measurements
(bill length, head-and-bill length, and tarsus length) did not vary be
tween first-or second-winter birds or adults. In contrast, wing length
, length of the eighth primary, mass and bill depth increased signific
antly with age for both sexes, although females attained their final s
ize quicker than males. Both wing length and body condition increased
throughout the winter. Possible explanations for these results are dis
cussed.