Bird Watch

No leaves on the trees is a distinct advantage and many birds will begin to sing or call in preparation for the breeding season.

Treecreepers Certhia familiaris are common and widespread in Britain, although perhaps harder to see than the more noisy and colourful species such as blue tits and nuthatches, with which they often associate in the winter flocks.

They are one of our more anonymous birds, difficult to see and their calls are rather indistinct, high-pitched and not particularly loud. As they do not migrate, they are not seen on passage in unusual locations.

They are found very much in wooded habitats and are rarely seen in gardens, unless they happen to border woodland or there are rows of mature trees.

Typically, they climb trees in a slow spiral investigating cracks and fissures in the bark, from which the thin, down-curved bill is used to pick out small invertebrates.

To find yourself a treecreeper in winter, look for other woodland birds first as they will often appear with flocks of long- tailed tits and others as they move through a wood.

Waiting for them to come to you is the best way, as they will often ignore humans if you remain quiet. They are white underneath but their upper parts are a perfect match for the tree trunks upon which they spend their time '“ different shades of browns and greys, flecked with white.

They have a long and quite broad tail, not obvious when the bird is high in a tree, but close up it is clearly used as a 'prop' with which they support themselves while ascending a tree. They climb facing upwards, although they can 'back down' trees a little way; this sets them apart from the nuthatch, which can climb headfirst down a tree trunk.

They are also very loyal to the trunk and large branches of a tree, rarely seeming interested in the outer branches or crown. This is presumably because smaller branches are not suited to the method in which they climb and the bark is lacking the nooks and crannies that hold hibernating insects.

Treecreepers are one of Britain's most sedentary birds '“ most stay within 20km of where they were reared. On the continent, some populations in the north do migrate short distances to avoid cold weather but for the most part they are as stay-put as they are here.

Another species of treecreeper (the short-toed treecreeper), found on continental Europe and present just across the English Channel, is only very rarely recorded in Britain. It is fair to say they are not great travellers.

Bird tables seem to hold no interest to treecreepers. Nuthatches, great spotted woodpeckers and all the members of the tit family take a variety of birdfeed but treecreepers do not. This is because they rely entirely on invertebrate food and do not eat seeds, fruits and nuts.

The old oak trees dotted around the reserve here at Pulborough Brooks is ideal habitat for them, just as it is for the nuthatches and woodpeckers, providing ample opportunity for nesting and feeding.

This feature was originally published in the West Sussex Gazette of February 13 2008. Read Birdwatch in the West Sussex Gazette every Wednesday.