Pecking and Respiration Rhythms of Pigeons

The production and coordination of rhythmic activities in birds is seldom investigated. Here we describe the pecking and breathing rhythms of pigeons under different conditions. When feeding from a heap of small grains, hungry pigeons pecked at regular intervals of about 0.3 s. The pecking rhythm was slightly slo,":,er in the afternoon. The pecking rhythm induced by the dopaminergic drug apomorphine was somewhat faster but some overt pecks were skipped. The mean respiratory cycle during a non pecking baseline condition lasted about 2.5 s. Breathing was slightly faster in the afternoon. During bouts of grain pecking, the breathing cycle shortened to about 1.7 s but returned to baseline soon afterwards. Under the influence of apomorphine, the respiration cycle duration was reduced to about 0.8 s. There was a relative interaction between the pecking and breathing rhythms, the pecks tending to occur at particular points of the inspiration and expiration phases. This partial entrainment was less pronounced during apomorphine-induced than grain-induced pecking. The mechanisms and functions that might be involved are discussed.