Dimorfismo sexual y diferenciación de edades en Sturnus unicolor Temm

Abstract

127 skins and 59 live specimens of Sturnus unicolor Temm. were studied from several Spanish localities in the hope of detecting differences related to age and sex. Biometric features, plumage pattern and other characteristics were examined with that purpose. The results are as follows: a) The Iberían population of Spotless Starling is quite homogeneous in its biometric measurements. b) Males (67 specimens) resulted to be significantly bigger than females (72 specimens) in the measurements of wing, tail and tarsus. On the contrary there was no significant difference in measurement of bill. c) Between males, adult ones were significantly bigger than juveniles of the first winter (eertainty index 99.5 ro), the group of adults showing a significantly bigger variance than those of the 1st. winter and 2nd year Spring (index 99.5 %). The other differential characters are considered across the differents seasons of the year namely Autumm and Spring, since the valid characters are: a) First winter subjects are spotted, the adults being uniformly black. b) The outline of the tail feathers is sharper in the adults. e) Adults males show longer feathers on the throat area than the males of the First winter. d) Sexes can be sorted as follows: animals with the edges of the wing feathers of a creamy gilt are females. Males do not show this feature. In Spring the valid characters are: a) For separating ages we use same of Autumm although with different applicability. b) When trying to sort animals of differents sex it is valid to use the same features as in Autumm plus the following two: -At this time females show base of bill of a pink flesh colour, males show a blue eolour in this area. -Females also show the iris bicoloured, males of an uniform colour.