Tuesday, 27 March 2012

A flurry of brown

With a whir of rust-coloured wings, a small bundle of brown can be seen flying between a scruffy, moss-covered stump and a thick column of ivy that clings to the trunk of a nearby Sycamore. The bird makes the trip several times, each time returning from the stump with a beak full of moss. This is a male Wren and he is busy building a nest to which he hopes to attract a mate.

The nest itself is soon discovered by watching the bird, a growing pile of moss pressed against the trunk and held in place by the mass of ivy tendrils and leaves within which it is placed. It looks as if much of the main structure has been completed, the bird now working on the top of what will become a neatly domed structure. The material around the entrance hole will be particularly tightly woven, allowing the bird to create a slight overhang, which affords the nest contents that little bit extra in the way of protection.

This is unlikely to be the only nest that this male will build over the coming weeks, since males construct a number of ‘cock’ nests, only one of which will secure the female’s approval. The favoured nest will be finished off with a lining of feathers. Some cock nests can appear a little rushed and are poorly constructed, giving the impression that the male is simply going through the motions – or it might be that the female has already selected another nest and he abandons the attempt mid-build. Most, however, are well built and look just like a finished and occupied nest, meaning that you cannot tell if a nest is active until you place a finger (or endoscope) inside and discover the soft lining. Even those nests that appear unused later into the season may suddenly come good, perhaps used for a second clutch or, in some instances, where the male takes on another mate.

Like most birds, it is during the period when building that Wrens are sensitive to disturbance. At this stage they have invested little in the breeding attempt and the cost of starting again somewhere else is low. For this reason, I will simply note the location of this nest from a distance, returning in a few weeks time to make a proper check. In the meantime I will return over the coming days to see if I can spot this particular male building other nests within his territory. He should be obvious enough, although this piece of damp woodland supports many male Wrens and it is not always that easy to work out where one breeding territory stops and the next begins.

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