Monday, 2 January 2012

Patriarch of the woods

In dawn’s half-light a dark silhouette sits hunched at the top of a tall birch. In one smooth motion it expands to a ragged-winged form to slip silently from its perch. This is a Carrion Crow, patriarch of these woods, and a territory-holding bird whose mate will be somewhere nearby. It is easy to see why these dark sentinels have featured so prominently in legend and lore. There is something ominous and broodingly expectant about the way in which they loiter, ever watchful for the next meal. Our interest in crows, and more widely in other members of the crow family, is rather ambivalent. Kept as pets, shot as pests, viewed with respect but sometimes fear, there is a long history that exists between us.

The Carrion Crow is an adaptable species, quick to learn and thus able to exploit new opportunities. They are one of the species to have benefitted from the new opportunities on offer in our ever-urbanising world. Even here, in the centre of town, a pair has taken up residence and can be heard proclaiming the ownership of their territory.

Crow populations can be divided into the territory-holding pairs and a floating population of non-breeding birds, the latter predominantly comprised of immature birds waiting for an opportunity to take on a territory. This suggests that territories are a limiting factor, the resources and nesting opportunities they contain restricted in their availability. Each territory, which can be up to 110 acres in size, is defended with vigour by the male, supported by his partner. Established neighbours, familiar to the territory-holding pair, are treated less aggressively, leading to some overlap in neighbouring territories and a shared defence of this airspace. In fact, neighbouring pairs may work together to chase off intruders and would-be predators like Buzzards.

During the nesting season, activity is centred on the nest and birds spend less time at the fringes of their territory. The males, however, continue to advertise the ownership with much calling and posturing. Birds from the non-breeding flock frequently test the resilience of established pairs by making territorial incursions, with such activity peaking during the first third of the year. Both the nest site and the breeding territory are defended throughout the year, so even now my local birds are on the lookout for possible trouble.

Despite the rigid territorial structure, Carrion Crows form large communal roosts (often with other crow species). These are a familiar feature of the winter months and are dominated by the non territory-holding birds, although territory holders may join them. For me though, it is the solitary pairs that sit and watch from their territories that are a feature of the dark winter mornings.

No comments:

Post a Comment