Dunking behaviour in Carib grackles

Dunking behaviour, the dipping of food in water, has been anecdotally observed in more than 25 species of birds in the wild, but its function and ecology have not been systematically studied. In experiments conducted in the field and in captivity on Carib grackles, Quiscalus lugubris, in Barbados, we showed that: (1) dunking rate in the field was influenced by food type and that moistening dry food seems to be one of the major benefits of dunking; (2) most dunking observed in the field was performed by a minority of individuals, but the vast majority (86%) of grackles tested in captivity were capable of dunking; (3) a higher density of conspecifics at a water source was associated with a lower dunking rate and an increased risk of kleptoparasitism when dunking; and (4) there were consistent individual differences in dunking and stealing frequency. We conclude that dunking is part of the normal behavioural repertoire of Carib grackles in Barbados, and that the low frequency of the behaviour in the field did not result from the inability of some individuals to perform the technique, but more likely from the balance of costs and benefits affecting its expression.