The incidence of nocturnal song by male Corncrakes Crex crex is reduced during pairing

Counts of singing male Corncrakes are often used to estimate population size, but they provide no information on the number of females. For much of the breeding season male Corncrakes sing almost continuously at night, but females ave inconspicuous and have not been recorded to sing in the wild. During radio-tracking studies, male Corncrakes were found to be singing on 92% of night-time checks when they appeared nor to have been accompanied by a female during the preceding day, but males accompanied by a female on the preceding day were only recorded singing on 12% of checks. Males were always silent when accompanied at night by a radio-tagged female. Wind speed and rainfall had no significant effect on the chance of it male being recorded singing. These findings suggest that surveillance of nocturnal song production could be used as a non-intrusive method of assessing whether male Corncrakes are attracting mates.