Using morphometry and molecular markers for sexing South American, Cayenne and Royal Terns breeding in Patagonia, Argentina

LISNIZER, N.; COTICHELI, L.; YORIO, P.; BASSO, N.; GATTO, A.

WATERBIRDS (DE LEON SPRINGS, FLA.)

WATERBIRD SOC

Año: 2014 vol. 37 p. 183 - 190

1524-4695

Data on the morphometry and sexual size dimorphism of the sympatric South American (Sterna hirundinacea), Cayenne (Thalasseus sandvicensis eurygnathus) and Royal (T. maximus maximus) terns from the Patagonia region in Argentina is reported. Data using discriminant analysis to sex the three species is reported. Morphological characters were obtained from South American Terns (n = 83), Cayenne Terns (n= 63) and Royal Terns (n = 20). All species were sexed using PCR-based molecular techniques. The three species showed significant differences in all body measurements, with the Royal Tern the largest species and the South American Tern the smallest. Sexes in the three tern species were only slightly dimorphic in size. Male Cayenne and South American terns were significantly larger than females in bill length, bill depth and head length. Royal Terns, in contrast, showed a high overlap in most morphological measurements, with head length being the only measurement that differed significantly between sexes. A discriminant function including bill depth, tarsus length, wing length, and head length correctly sexed 89% of South American Terns, while a function including bill depth and head length correctly sexed 78% of Cayenne Terns. Head length was the only variable that significantly discriminated sex in Royal Terns, allowing gender identification in 75% of cases. Our results provide a valuable tool for rapid sexing in the field of these three Patagonian terns, although reliable sexing in Cayenne and Royal terns should be preferentially achieved using a combination of morphometric and molecular sexing.