SEX DETERMINATION IN GLOSSY IBIS CHICKS BASED ON MORPHOLOGICAL CHARACTERS

SUMMARY.—Sex determination in glossy ibis chicks based on morphological characters. Aims: We derived two discriminant equations to sex glossy ibis Plegadis falcinellus chicks (2- 5 we-eks old) based on morphological characters. Location: Doñana, South-West Spain. Methods: Wing length and tarsus length and width of 198 individuals were measured in the 2002 and 2003 breeding seasons. Results: Tarsus width was the most discriminant character and in combination with wing length allo-wed us to sex 86.9 % of individuals correctly. A formula based on wing and tarsus length also sexed 84.9 % of individuals correctly. The reliability of this second equation was also tested with an independent sam-ple of 209 individuals measured in 2004, with error rates similar to those of the original data. Intervals for discriminant scores reducing errors in sexing to 10 % or 5 % were derived, at the cost of reducing the proportion of individuals that can be sexed. These equations should not be applied in other localities wi-thout validation, but our analyses suggest they can be used on different cohorts. We also describe a vi-sual sexing technique found to have 95 % accuracy for an experienced observer. Conclusions: Sex can be reliably determined for many glossy ibis chicks. Given the considerable se