'creepers' (10 February 2004)

Whilst recently handling several Treecreepers Certhia familiaris I was thinking about the specialised adaptations for the species' lifestyle:

- their long, sharp claws help them in climbing up trees:

- the stiffened tail feathers (seen here from above and below) are good for propping themselves against tree-trunks:

- their long, thin, curved bill is a great tool for probing the crevices in bark where their insect prey is likely to be hiding:

- and the mottled mixture of shades of brown in their back plumage provides excellent camouflage when seen against a tree trunk:

All of these features are virtually identical in the North American Brown Creeper Certhia americana, until recently considered by some authorities to be the same species, and officially split by the American Ornithologists' Union only in 1982. This is one that I photographed during my visit to Braddock Bay Bird Observatory, near Rochester, New York, 26 September 2003:

My recent time catching birds in Mexico introduced me to another family of 'creepers', the woodcreepers Dendrocolaptidae. Our small team, Mike Lanzone and Adrienne Leppold from Powdermill Nature Reserve, and I, saw several woodcreepers but only caught one species, the Olivaceous Woodcreeper Sittasomus griseicapilus. I am not sure how this species acquired its common name, because 'olivaceous' is not the adjective that comes to mind on seeing its rusty back and tail, and brown wings with obvious tan-coloured patches, but the scientific name of 'grey-capped' does seem appropriate:

Woodcreepers have an even more extreme tail adaptation than the Certhia family, with every rectrix having a vane that is stiffened and bent at the tip, curving outwards and downwards, as shown in the photograph:

Finally, another species that shares some aspects of the 'creeper' life, but does not have the name of 'creeper', is another North American bird, the Black-and-White Warbler Mniotilta varia. This photograph shows an adult (after hatching-year) male that I handled at Powdermill Nature Reserve on 5 October 2003:

The Black-and-White Warbler finds insects by creeping along tree-trunks and branches, but this species has a normal tail, without any stiffened vanes. Its feet and claws, however, are very similar to those of the Certhia family:


David Norman


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