干旱区生态环境知识资源中心

We review intra- and interspecific brood parasitism in herons, and describe new cases for Little Egrets (Egretta garzetta), Cattle Egrets (Bubulcus ibis), Squacco (Ardeola ralloides) and Purple Herons (Ardea purpurea) breeding in the Ebro Delta, Spain. We report also a case of a Little Egret chick that was successfully reared by Squacco Herons. We experimentally evaluated antiparasitic responses to simulated intra- and interspecific parasitism using dummy eggs. Large dummy eggs corresponded in size with normal Cattle or Little Egret eggs, while small dummy eggs were equivalent to the size of normal Squacco Heron eggs. Both egret species and Squacco Herons, deserted their nests significantly more frequently when a large egg was added to the clutch. Thus, the egret species were more responsive to simulated intraspecific parasitism while Squacco Herons were more responsive to simulated interspecific parasitism. Size asymmetries between host and parasite, hatching asynchrony brood reduction and nest-guarding all seem to be important to the evolution of brood parasitism in herons.