Effect of artificially increased day length in winter on female domesticated canaries

Abstract

Three groups of female canaries were given different schedules of increasing day‐length between October and December: all groups responded in the same way. Three groups of female canaries were given a 20 hour light/four hour dark schedule at different periods outof the breeding season (October‐December, October‐January, and January‐February).All experimental birds became defeathered and vascular. There was an increase in skin tactile sensitivity in October‐December but not in January‐February. Nest‐building was induced in all months. Only six out of 41 experimental birds laid eggs. Eleven birds which did not lay showed marked incubation behaviour. Discussion centres around the hormonal control of brood patch formation. The possibility that the absence of an effect of photostimulation on sensitivity in January‐February is due to shortage of progesterone is considered. These light schedules induced more nest‐building than injected oestrogen: no conclusions are yet possible on the hormonal control of next‐building.