Domestic pigeons: the stimulus provided by the egg in the nest.

Abstract

SUMMARY The effectiveness of various isolated tactile or visual stimuli in maintaining brooding behaviour in pigeons has been studied. It was found that: In the light (1) The presence of any number of eggs in the nest, whether greater or fewer than the normal clutch size, is equally effective in maintaining brooding behaviour. (2) Any solid model of the approximate size of the natural egg may be an effective stimulus to brooding. (3) Flat oval models, or even the eggs themselves if physical contact with them is prevented, are not effective. (4) Simple stimulation of afferent nerve endings of the apterium is not an effective stimulus in the absence of the egg. (5) Total denervation of the skin of the apterium does not diminish the effective stimulus provided by the natural egg. (6) If prevented from tactile (but not visual) contact with the male, nest bowl and eggs, incubating behaviour in the female continues only so long as the male continues to brood. In the dark (7) Solid egg-shaped models are an effective stimulus for normal birds. (8) Normal incubating behaviour may or may not be maintained after denervation of the apterium. It is concluded that, in the domestic pigeon with previous breeding experience, no one class of sensory receptors and no one afferent route are concerned in the neural pathway conveying the stimulus provided by the present egg to the hypothalamus.