Frequency and intensity of chick distress calls: Effects on maternal foodcalling in chickens.

The food call of broody domestic hens was used to measure maternal response to four frequency components found in chick distress calls (2,3,4 and 5 kHz) and to variations in distress call intensity (0-86 dB). Foodcalling increased significantly with frequency of the pure-tone test pulse; response to a taped distress call occurred between 40 dB and 86 dB intensity with a maximum at 60-65 dB. The results suggest that the mother uses the higher frequency components in recognizing the distress call, but responds maximally within a specific intensity range. The selective advantage of such behaviour is discussed.