Neck-collars are commonly used to identify geese and swans, but possible adverse effects of collars have been investigated in few species. We evaluated the effects of plastic neck-collars on the behaviour and condition of Black Swans (Cygnus atratus). We fitted 67 individuals with rigid, plastic neck-collars between July and November 2007, and three months later compared the behaviour of a sample of 16 collared Swans with that of 16 uncollared birds. There were no differences between collared and uncollared Swans in the percentage time spent resting, swimming or preening. Collared Swans tended to spend less time upending and more time dabbling than uncollared Swans, but the overall proportion of time spent foraging was similar, and the difference in preferred foraging mode did not result in differences in body condition. We suggest that neck-collars are suitable for identification of Black Swans.