Co-ordination between the activity of the heart and the flight muscles during flight in small birds

Abstract

1. 1. The heart rate during rest was 7/sec in the budgerigar and 10/sec in the finch. 2. 2. In the budgerigar the maximal heart rate during flight was equal to the wing beat rate (15·5/sec), while in the finch it was half the wing beat rate (32/sec). 3. 3. There were no obligatory links between the activity of the heart and the pectoral muscles during flight; however, the heart was rarely activated simultaneously with the pectoral muscles. 4. 4. It is concluded that the pectoral muscles in small birds may work like a “venous pump” during flight by contracting every time the heart is in diastole.