EMBRYONIC HEART-RATE IN ALTRICIAL BIRDS, THE PIGEON (COLUMBA-DOMESTICA) AND THE BANK-SWALLOW (RIPARIA-RIPARIA)

Ballistocardiography or impedance cardiography was used to measure on a daily basis the heart rate (f(H)) of embryos of altricial pigeons (C olumba domestica) and bank swallows (Riparia riparia). The patterns of f(H) changes during development were investigated. Embryonic f(H) of domestic and homing pigeons increases slowly during the middle stages of development and then increases sharply toward the end of incubation . Fantail pigeons show a different pattern of embryonic f(H) change; t hat is, f(H) remains constant until 1-2 d prior to external pipping an d increases thereafter. Heart rate of the bank swallow increases conti nually throughout the last half of the incubation period. The developm ental patterns of f(H) changes in pigeons and swallows generally are d ifferent from those of most precocial birds, in which embryonic f(H) d ecreases during the last stages of prepipping development.