Eurasian Treecreeper Bird is a slight bird with a long and slender shape, a thin decurved bill and a long, stiff and 'spiky' tail. It creeps up tree trunks like a mouse, often starting at the base and then climbing up before dropping down to the base of an adjoining tree and starting again. It is essentially bark-coloured above, with a complex pattern of brown finely marked with whitish spots and streaks. It is white below, faintly tinged with brown on the rear flanks and vent, and has a white supercilium that is strongest behind the eye.
Eurasian Treecreeper Bird is a resident and arboreal bird, found in deciduous, mixed and coniferous forest. In Britain it favours broadleaved woodland, often where quite dense, but commonly in small marginal patches of trees in farmland, hedges, parks, large gardens and in riverine strips of alder and other species. It requires bark with crevices for feeding, with decaying wood and loose and flaky bark needed for nesting and roosting. Where its range overlaps with the Short-toed Treecreeper, it is generally found in more montane and coniferous areas.
The song of Eurasian Treecreeper Bird is a very high-pitched, regularly structured little ditty lasting 2-2.5 seconds, starting with high flat notes and then accelerating and descending in tone before a flourish at the end. The penultimate note is the lowest of the sequence and the final note is rather higher, such as "tseee, tsee'tsee tsi'sisisisi sisoo'wit". Variations occur, and where both treecreeper species occur together, this one may mimic the other! The calls are also very high pitched, as high as a Goldcrest at 8.5kHz, as in the short and often repeated contact call "zssii" or "tiih", sometimes given with a dipping inflexion, such as "tsu'ui", as well as a harsher, slightly buzzing "zsih'h'h'h" and a more trilling, high and flat "tsirrrr".