Eurasian treecreeper | Certhia familiaris

Voice

This is where the case is decided. The call is a thin, high, sibilant srreeh with a slight vibrato and a drawn-out quality — far more attenuated and piercing than the full tyoot of short-toed treecreeper, and pitched high enough that older ears routinely miss it. There is also a fine tsee. The song runs two to three seconds and is clearly longer, higher and more musical than the short hard phrase of its twin: a thin cascade that falls away in pitch and curls upward into a closing figure at the end, Blue Tit-like in timbre. One caution belongs with it: in the overlap zone males of both species take up each other's phrase, and birds are documented that command both songs. The call is the more dependable of the two.

Identification

At any distance, a treecreeper and nothing more: small, mouse-like, brown and spangled above, pale below, with a long curved bill and a stiff pointed tail braced against the bark. Every difference from its twin is one of degree. The underparts are whiter and cleaner, without the dingy buff or brownish wash on flank and lower belly. The upperparts are warmer and more rufous in tone and more contrastingly spangled, the white spots standing out more sharply. The supercilium is a cleaner white, more crisply bounded, and runs noticeably further behind the eye; on the best birds the two brows look as if they nearly meet across the nape. The pale band across the primaries carries an obvious projecting step. The bill averages shorter and the hind claw longer. Individually not one of these will carry a record in poor light.

Confusion species

In Britain and Ireland there is no confusion species at all, and this freedom is worth using: it is the place to fix in the mind what a clean white belly and a long white supercilium actually look like, so the Continental comparison later has a baseline. Elsewhere everything turns on short-toed treecreeper — see its own species page, where the same difference is set out from the other side. That bird is duller and greyer above, dingy to buff on flanks and lower belly, with a weaker and shorter supercilium, a flatter wing band, a longer bill and a shorter hind claw. None of those characters survive backlighting, rain or a high, shaded canopy, and a badly lit Eurasian treecreeper can suggest every mark of a short-toed. In Spain the rule of thumb is geographic before it is morphological: below the montane belt, and outside the Pyrenees and the Cantabrian range, a treecreeper is always short-toed; in the high-mountain conifers of those two ranges, listen before you note it down. Without a call or song a treecreeper elsewhere should not be logged as Eurasian — however white the belly looks. Nuthatch is heavier, blue-grey with rusty flanks, a black eye-stripe, a straight bill and no propping tail, and climbs head-down. Wren hops, is round and cocks a short tail.

Habitat

Conifer and mixed forest are the core: spruce and pine, old mossy stands with plenty of dead wood, montane forest up to the tree line. Where short-toed treecreeper is absent — Britain, Ireland, Scandinavia and much of Russia — it takes broadleaved woodland, parks and gardens as readily, which shows that the constraint is not the tree but the neighbour. In Britain it uses mature oak and beech woodland, wooded parkland, conifer plantation and even large gardens, and it has a well-known liking for the soft fibrous bark of planted giant sequoias, in which it gouges oval roost hollows. The nest goes behind a loose plate of bark or in a narrow crevice.

Range and movements

From Ireland and Scotland across Scandinavia, the Baltic and Russia to Japan, Korea and northern China, with southern outliers in the Pyrenees, the Cantabrian Mountains, the Alps, the Carpathians, the Balkans, Turkey and the Caucasus. A large part of that range lies far outside Europe. In Britain it is a widespread and largely sedentary resident of perhaps two hundred thousand territories, absent only from treeless uplands and the outer isles. In Spain the population is small and mountain-bound, split between the Pyrenees — from Navarre to Catalonia — and the Cantabrian ranges, resident apart from altitudinal shifts in hard winters. In the Netherlands two separate stories run side by side: Scandinavian birds appear from October as a scarce autumn and winter visitor, mainly on the Wadden islands and in the coastal dunes, while the central European form has bred in small numbers in southern Limburg since 1993 and is slowly spreading along the eastern border. Both remain rare.

• Resident
• Breeding (summer)
• Winter
• Passage
• dark = core range, pale = thinly spread

How and when to look

Look for it where the odds are best and the comparison sharpest. In Britain, use winter tit flocks: walk mature woodland from November to February, wait for the flock, and pick out the very high, thin srreeh among the Goldcrest and coal tit calls. In frosty weather check any planted sequoia in a park or churchyard for oval roost hollows at chest height, and stand back at dusk. In the Netherlands, a search over Vlieland, Terschelling or Schiermonnikoog after a north-easterly in October and November gives the best chance of a Scandinavian bird; in the bare dune scrub every treecreeper is worth checking, and listen especially for the call. For the breeding bird, go to the slope woods of southern Limburg in March and April — the Vijlenerbos and the Bunderbos are proven addresses — and listen from sunrise for a phrase longer and more musical than the one you know from home. In Spain the best way to get to know it is a spring walk uphill: go in May or June to a spruce or beech wood in the Pyrenees above twelve hundred metres — the Ordesa valley, Irati or the Catalan Pyrenees all work — and listen from dawn for the long, falling phrase with its final flourish, clearly different from the short, dry song of the common treecreeper singing lower on the slope; the mature beechwoods of the Picos de Europa in the Cantabrian range offer the same chance. For the comparison without a travel plan: in the German Eifel, the Ardennes and the Vosges both species sing in the same valley, one down in the broadleaf woodland and the other up among the spruce.

Conservation status

Not globally threatened, and common to abundant across an immense boreal and montane range. In western Europe local declines follow the felling of old conifer stands and the removal of dead wood, and in Britain and Ireland a slow decrease has been recorded that is often linked to wet summers chilling nestlings behind rain-soaked bark. Elsewhere the trend is stable. Mature forest left standing, with rough-barked veterans and loose bark plates, is all the species asks for.

Scientific name

Certhia familiaris | Linnaeus, 1758

Linnaeus described the species in 1758 and placed it straight away in the genus where it still stands. He introduced the genus Certhia in that same work. Certhia is from Ancient Greek kerthios, a small tree-dwelling bird described by Aristotle and others. familiaris is Latin for 'familiar' or 'common'. The specimen the first description was based on came from Sweden.