Cardiac response of starlings to sound: effects of lighting and grouping

Abstract

The heart rate of wild starlings (Sturnus vulgaris) isolated in an acoustical chamber was monitored by miniaturized FM transmitters attached to the birds. The normal heart rate of 14 single birds was significantly higher (P < 0.01) during simulated day than during night when the birds were inactive, but there was also a peak at night. When a frightening sound stimulus (recorded starling distress call) was played for 10 sec. to the birds in the chamber, the heart rate showed an immediate sharp rise, peaking within 3 sec. after the sound began and then gradually decreasing toward the base-line (undisturbed) heart rate. The initial response of 26 single birds to the stimulus was greater during the day, but the decrease toward base line was slower at night, resulting in a significantly higher (P< 0.025) average total response at night. The initial response was lower and the decrease faster when each of 22 birds was alone than when in a group of 4 other starlings, resulting in a significantly higher (P< 0.025) average total response for birds in a group.