Black swans engage in a behaviour known as crèching or brood amalgamation. Some time after hatching, cygnets from different broods move from one family to another and so end up being reared by adults other than their genetic parents. A variety of hypotheses have been developed to explain why individuals should engage in this curious behaviour. In this paper, Ken finds that adopted cygnets are more closely related to their ‘foster’ parents than they are to most other swans in the population, raising the intriguing possibility that brood amalgamation involves close relatives.
KRAAIJEVELD, K. (2005). Black swans Cygnus atratus adopt related cygnets. Ardea 93: 163-169
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