EGG AND NEST RECOGNITION BY 2 TERN SPECIES (STERNIDAE-AVES)

Colonial ground-nesting birds may nest in very dense aggregations, and their ability to recognize their own nests has obvious consequences f or individual fitness. We conducted field experiments, simulating natu ra!events, designed to evaluate the importance of egg, nest, and habit at characteristics for nest recognition by Common and Little terns. Co mmon and Little terns differed in the use of landmarks for nest identi fication Little terns discriminated their own eggs from foreign eggs, but Common terns did not. Little terns retrieved foreign eggs. The dif fering cues used by the two species may represent adaptations to the p revailing habitat features of their colonies: open sites for Little te rns compared with vegetated sites for Common terns.