Wildlife Column: Bird with mouse-like behaviour...
One of my favourite little birds is the treecreeper or Certhia familiaris, a diminutive andoften overlooked ‘small brown job’.
This tiny tree-climber is brown on its uppers and white underneath, with a distinctive downward-curved bill, and long, pointed tail. It uses the latter (which has protruding shafts) to prop itself against vertical tree-trunks as it climbs nimbly upwards. Its typical behaviour is to fly down to ground level and then climb in a circular fashion up the trunk searching for tiny insects and spiders with its recurved beak; which is a little like a surgeon’s forceps. The treecreeper is probably more common than generally realised as it tends to be rather shy and will often move silently around to the far side of a tree in order to be out of view of inquisitive watchers. In winter they join up with tit flocks or at least interact with them as they pass through woodland-edge habitats. The call is rather like the goldcrest with a thin but insistent, ‘tsee-tsee’. With its secretive, almost mouse-like behaviour this is a bird to look out for. They are primarily a woodland species but will come to gardens with largish trees, and to parks and hedgerows. Their nests are usually cup-shaped and neatly placed behind tree-bark on older trees and the territorial singing has been described as ‘a very sweet little wisp of a song’. This is a tremulous descending ripple with a terminal flourish; so listen out for that!
Whilst the treecreeper may nip niftily behind a tree, their other strategy on being aware of being spotted is to freeze and simply pretend that you can’t see them. With their speckled brown plumage that can work quite well. Generally you will only see single birds or pairs but sometimes in cold weather they group together at communal roosts in order to keep warm and in that case you may, in winter, come across a small flock. Not altogether the brightest bird we have, if you stand still, the youngsters sometimes mistake people for trees. They have been known to climb up a person!
Professor Ian D. Rotherham, of Sheffield Hallam University, researcher, writer and broadcaster on wildlife and environmental issues.