Criteria for Sexing and Aging European Starlings (Sturnus vulgaris)

The following study on age and sex criteria in the European starling (Sturnus vulgaris) is based on the results of a three-year field study at Ithaca, New York.During .thistime over 1000 birds have .beenexamined, and a collection of a'bout 350 skins has been made as a reference collection.Many of the results of this study corroborate the works of earlier authors--Dwight (1900), Harrison (1928), Hicks (1934), •Banzhaf (1937), Witschi and Miller (1938), Bullough (1942a, 1942b), and others.Additional criteria have been noted and some of the previous work put on a more definite basis.SEX CRITERIA The final criterion of sex is the gonad; frequently this is the only known method of sexing an animal.The examination of gonads is not feasible, ,however, when studies require the use .ofliving birds.In the European starling there are at least two external characters that are quite reliable as sex criteria.The color of the rami of the lower mandible during the breeding season is one of these.It is pale pink in the female, and blue to blue-black in the male.This character is useful from November through the breeding season, during which period the rest of the bill is either completely yellow or has the yellow pigment in the basal region.The developing yellow in the .billadvances from the base toward •the tip, showing first at the base of the lower mandible in late November.After the proximal two-thirds has become yellow it is possible to use the color of the mandibular rami as a reliable sex indicator.Immediately following the nesting season the bills begin to darken, coincident with the start of the post-nuptial molt.As this darkening process likewise begins at the proximal end of the bill, the pink or blue coloring becomes masked and the character is no longer valid.In 600 yellow-billed birds examined for this character and then dissected, the color of the base of the bill gave complete accuracy.In dried museum skins, the dimorphic color of the rami is still a reliable ,cri, teria for sexing starlings: In the males the color deepens to almost black, while in the females the pink may fade, leaving the rami creamcolored.The color of the eye is another character that can be used as a sex criterion in starlings.Although the eyes are not quite as reliable as the color of the lower mandible, they can be used during the entire year.In the male starling the iris is a deep brown color throughout; in the female the outer edge of the iris becomes yellowish, making a lightcolored, conspicuous ring around it.Usually this difference is distinct, and some females show the character when only six weeks of age.Occasionally, however, the yellow ring in the female eye is difficult to discern; or at times in the male eye a faint, light ring is discernible about the iris, but it is farther back under the eyelids and much less distinct than in most females.