Responses of brooding Australasian Grebes Tachybaptus novaehollandiae to other waterbirds

Abstract

A breeding pair of Australasian Grebes Tachybaptus novaehollandiae was monitored nearly daily between November 2010 and March 2011. This paper describes the responses of the adults to other waterbirds that came within 5 m of their brood, either provoked or unprovoked. Brood loss was rapid, with only one of five chicks surviving more than 3 weeks. Nine instances of brood-defence were recorded, mostly in the first 2 weeks after hatching, as well as one observation of a chick defending itself. The Dusky Moorhen Gallinula tenebrosa was the main species that prompted reactions from the adult Grebes. A Moorhen was seen trying to prey on Grebe chicks on one or probably two occasions, the first time this has been reported. A Purple Swamphen Porphyrio porphyrio was also attacked by the Grebes, and is a likely potential predator of grebe chicks. Ducks and cormorants were attacked or tolerated on different occasions.