 On the breeding grounds , the male corn crake 's advertising call is a loud , repetitive , grating krek krek normally delivered from a low perch with the bird 's head and neck almost vertical and its bill wide open . The call can be heard from 1 @.@ 5 km ( 0 @.@ 93 mi ) away , and serves to establish the breeding territory , attract females , and challenge <unk> males . <unk> differences in <unk> mean that individual males can be distinguished by their calls . Early in the season , the call is given almost continuously at night , and often during the day , too . It may be repeated more than 20 @,@ 000 times a night , with a peak between midnight and 3 am . The call has evolved to make a singing male 's location clear , as this species hides in vegetation . The frequency of calling reduces after a few weeks but may intensify again near the end of the laying period before falling away towards the end of the breeding season . To attract males , mechanical imitations of their call can be produced by rubbing a piece of wood down a notched stick , or by <unk> a credit card against a comb or <unk> @-@ <unk> . The male also has a growling call , given with the bill shut and used during aggressive interactions . 
