The Grey tit (Parus major caschmerensis) in Northern India: Behaviour and Ecology in the non-breeding season

Abstract

Studied the grey tit (Parus major caschmerensis) in Naina Devi Sanctuary. in the Shivalik hills of the Himachal Pradesh Himalaya. This is a subspecies of the well-studied great tit which ranges over a large part of Eurasia. The study had two main components: a. to investigate the non-breeding behaviour and ecology of this bird in India, and to interpret the findings with respect to what is known about the species from more northern areas (a comparative approach). b. to study the behaviour of individuals in the context of short· and long-tenn processes (in the winter, examples of these might be survival and reproduction. respectively), I collected data on colour-banded grey tits by following individuals, and recording behaviour using the point-sampling technique with one-minute intervals. Field work was carried out between December 1994 and April 1995. Throughout this study, I refer to the subspecies in India as grey tits, those studied in Europe and Japan as the great tit, and to the species as a whole as Parus major. In a comparison with what is known about great tits, the following points emerge: .Grey tits do not spend the winter in flocks of conspecifics; instead. they are either solitary or in pairs. This is associated with comparatively high winter temperatures, and may be the result of a low seasonality in resource abundance allowing for greater territorial site-fidelity. Sexual dimorphism in bill shape mirrors that found in a previous study on great tits in England, where males have deeper and shorter beaks than females, tend to forage more on beech seeds, and are more efficient at doing so than females. Grey tits show a sexual dimorphism in beak shape paralleling this, and males exhibit a strong tendency to forage more on Acacia catechu (from which largely pods are taken) than females, implying that similar ecomorphological processes can operate in populations widely separated in space. Grey tits use a wider variety of foraging substrates than their more northern counterparts, and correspondingly spend less time foraging on the ground. This is' associated with the absence of any congeners, although whether it is a case of competitive release is open to dispute. The Indian birds seem to spend more time feeding than what has been reported for English great tits. The greater time spent feeding is perhaps unexpected given the comparatively higher winter temperatures, and longer day-lengths in Naina Devi than in northern Europe. While a strict comparison of different studies may not be entirely valid, the solitary/pair living habit of grey tits may result in lower levels of aggression, and this may allow for more feeding time. The date of laying is related to the duration for which the male and female have been together (i.e pairing date). Birds which paired early bred early, though this is based on a limited sample of four pairs. If this relationship is causal, and if reproductive success decreases through the breeding season (as has been shown for many temperate species), it would imply a strong selection pressure for early pairing in the great tit. As breeding approached, males spent less time feeding than in the winter, and were involved in greater territorial activity such as singing. Female time budgets showed a similar, though nonsignificant trend over the season. Pooling sexes, the proportion of time spent tended towards a decrease as summer drew near. This decrease approached statistical significance.