Sex determination based on morphometric measurements in yellow-legged gulls (Larus michahellis) around Istanbul.

Background: Yellow-legged gulls (Larus michahellis), commonly found in Istanbul and their surroundings, have a monomorphic plumage, like other gull species. For this reason, sex determination cannot be made externally. In this study, a total of 60 adult Yellow-legged gulls, 33 males, and 27 females, collected from the coastal areas of Istanbul, were examined. Discriminating functions were developed to classify males and females using birds that were previously sexed by DNA analysis and abdominal dissection.

Results: Head length and bill depth were selected to build the discriminant function by the stepwise analysis. The function classified male gulls with an accuracy of 97.0% and females with an accuracy of 92.6%. Head length alone is the most accurate predictor in terms of the percentage of correct sex determination (90.9% for males, 92.6% for females).

Conclusions: Functions that can easily determine sexual dimorphism for the population of Larus michahellis gulls around Istanbul have been put forward for the first time.