2025/09/17 by Teresa Catry, José P. Granadeiro, Edna Correia · 1 voice
Environmental Science · Agricultural and Biological Sciences · #Wildlife Ecology and Conservation #Avian ecology and behavior #Animal Behavior and Reproduction
paper · doi:10.1675/063.048.0204
In species exhibiting sexual size dimorphism (SSD) but no plumage dimorphism, morphometric sexing using linear discriminant analysis (LDA) may offer an efficient and economical alternative to molecular methods in field studies. Despite their importance, published discriminant functions remain scarce for many avian families, namely the Threskiornithidae, which includes ibises and spoonbills. In this study, Glossy Ibis (Plegadis falcinellus) were captured in rice fields in Portugal and sexed using molecular techniques. Morphometric measurements—wing length, culmen length, tarsus length, and body mass—were recorded, revealing significant male-biased SSD across all metrics. Males were, on average, 24% heavier and exhibited 19%, 18%, and 7% longer tarsus, culmen, and wing lengths, respectively. Univariate discriminant functions using wing or tarsus length alone correctly classified 96% of all measured individuals, while a multivariate function including wing, culmen and tarsus length achieved 100% of accuracy. Eleven equations with one or more variables correctly assigned 100% of the females to their sex-class while classification accuracy for males ranged between 93 and 100%. Our findings highlight the effectiveness of morphometric methods for reliable sexing Glossy Ibis and provide a practical tool for future ecological studies requiring sex determination.