The effects of mate and nesting facilities on the occurrence of egg-laying were examined in the Bengalese finch.

Egg-laying is unusual in isolated females and those kept in large groups. It is more common in monosexual pairs, and its incidence in them is not markedly altered by whether males can be heard or not. Females in heterosexual pairs usually lay within three weeks of pairing. A similar lag was found in pairs separated by bars, pointing to copulation being unnecessary.

Carrying of nest material to the nest box is mainly done by males. It is unusual in isolated birds, but occurs in monosexual and heterosexual pairs, and in pairs separated by bars.

Egg-laying is delayed in the absence of hay for nest building. A delay was also found in pairs separated by bars, when only the male was given nest material: this indicates that personal experience by the female is important. Heterosexual pairs deprived of nest boxes, but given nest material, were not recorded as laying.

It is concluded that egg-laying is stimulated by mate and nest material in a complex fashion. The various stimuli these provide interact to a greater or lesser degree to give the physiological and behavioural changes observed.