Circadian Rhythm Determines the Timing of Activity, and Ingestive and Grooming Behaviours in Indian House Crows, Corvus splendens

Abstract

Corvids show an episodic memory with the temporal information on 'when' an event has actually occurred. We propose that crows keep the time and duration of an event by involving the endogenous circadian clocks, reliably measured in behavioural rhythms. The aim of the present study is to find out if circadian rhythms were involved in the organization of daily behavioural patterns in Indian house crows, Corvus splendens . We monitored the activity, ingestive (feeding: eating and drinking) and grooming (preening) behaviours in crows sequentially exposed to 12 h light : 12 h darkness (12 L : 12 D) and dim constant light (LL dim ) for one and three weeks respectively. The behavioural patterns were synchronized and diurnal was under 12 L : 12 D, while freeran had a circadian period under the LL dim . In general, eating and drinking, not grooming, patterns were more closely related to the activity - rest cycle. These results show the persistence of circadian rhythms in behavioural patterns, and extend the idea that endogenous circadian clocks determine daily timing of the physiology and behaviour in Indian house crows, in particular, and birds, in general.