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In page Crex:

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The advertising calls of both crakes are readily distinguished from the quite dissimilar calls of potentially sympatric rails such as the spotted crake, striped crake, Baillon's crake,[4] or water rail.[5] The calls of the two Crex species cannot be confused, since the corn crake is silent in Africa.[6] Both sexes may give distinctive territorial or alarm calls, and females and chicks communicate with cheeps and wheezes. The African crake can be attracted to within 10 m (33 ft) of a human by imitation of its kraaa threat call,[1] and the male corn crake by mechanical imitations of their advertising call, including rubbing a piece of wood down a notched stick, or by flicking a credit card against a comb or zip-fastener.[3]