Encyclopædia Britannica, Ninth Edition/Tree-creeper
TREE-CREEPER, one of the smallest of British birds, and, regard being had to its requirements, one very gene rally distributed. It is the Certhia familiaris of ornithology, and remarkable for the stiffened shafts of its long and pointed tail-feathers, aided by which, and by its comparatively large feet, it climbs nimbly, in a succession of jerks, the trunks or branches of trees, invariably proceed ing upwards or outwards and generally in a spiral direction, as it seeks the small insects that are hidden in the bark and form its chief food. When in the course of its search it nears the end of a branch or the top of a trunk, it flits to another, always alighting lower down than the place it has left, and so continues its work.
Inconspicuous in colour, for its upper plumage is mostly of various shades of brown mottled with white, buff, and tawny, and beneath it is of a silvery white, the Tree-Creeper is far more common than the incurious suppose; but, attention once drawn to it, it can be frequently seen and at times heard, for though a shy singer its song is loud and sweet. The nest is neat, generally placed in a chink formed by a half-detached piece of bark, which secures it from observation, and a considerable mass of material is commonly used to partly stuff up the opening and give a sure foundation for the tiny cup, in which are laid from six to nine eggs of a translucent white, spotted or blotched with rust-colour. The Tree-Creeper inhabits almost the whole of Europe as well as Algeria, and has been traced across Asia to Japan. It is now recognized as an inhabitant of the greater part of North America, though for a time examples from that part of the world, which differed slightly in the tinge of the plumage, were accounted a distinct species (C. americana), and even those from Mexico and Guatemala (C. mexicana) have lately been referred to the same. It therefore occupies an area not exceeded in extent by that of many Passerine birds, and is one of the strongest witnesses to the close alliance of the so-called Nearctic and Palæarctic Regions.
Allied to the Tree-Creeper, but wanting its lengthened and stiff tail-feathers, is the genus Tichodroma, the single member of which is the Wall-Creeper (T. muraria) of the Alps and some other mountainous parts of Europe and Asia, and occasionally seen by the fortunate visitor to Switzerland fluttering like a big butterfly against the face of a rock, conspicuous from the scarlet-crimson of its wing-coverts and its white spotted primaries. Its bright hue is hardly visible when the bird is at rest, and it then presents a dingy appearance of grey and black. It is a species of wide range, extending from Spain to China; and, though but seldom leaving its cliffs, it has wandered even so far as England. Merrett (Pinax, p. 177) in 1667 included it as a British bird, and the correspondence between Marsham and Gilbert White (Proc. Norf. and Norw. Nat. Society, ii. p. 180) proves that an example was shot in Norfolk, 30th October 1792; while another is reported (Zoologist, ser. 2, p. 4839) to have been killed in Lancashire, 8th May 1872.
The genus Certhia, as founded by Linnæus contained 25 species, all of which, except the two above mentioned, have now been shewn to belong elsewhere; and for a long while so many others were referred to it that it became a most heterogeneous company. At present, so few are the forms left in the Family Certhiidæ that systematists are not wanting to unite it with the Sittidæ (cf. Nuthatch), for the two groups, however much their extreme members may differ, are linked by so many forms which still exist that little violence is done to the imagination by drawing upon the past for others to complete the series of descendants from a common and not very remote ancestor, one that was possibly the ancestor of the Wrens (q.v.) as well. One thing, however, has especially to be noticed here. The Certhiidæ have not the least affinity to the Picidæ (cf. Woodpecker, infra), but are strictly Passerine, though the Australian genus Climacteris may possibly not belong to them. (a. n.)