and spiders from crevices in the bark. Although normally found on trees, it will occasionally hunt prey items on walls, bare ground, or amongst fallen pine needles, and may add some conifer seeds to its diet in the colder months. The female Eurasian treecreeper forages primarily on the upper parts of the tree trunks, while the male uses the lower parts. A study in Finland found that if a male disappears, the unpaired female will forage at lower heights, spend less time on each tree and have shorter foraging bouts than a paired female. This bird may sometimes join mixed-species feeding flocks in winter, but it does not appear to share the resources found by accompanying tits and goldcrests, and may just be benefiting from the extra vigilance of a flock. Wood ants share the same habitat as the treecreeper, and also feed on invertebrates on tree trunks. The Finnish researchers found that where the ants have been foraging, there are fewer arthropods, and male treecreepers spent a shorter time on spruce trunks visited by ants. Habits As a small woodland bird with cryptic plumage and a quiet call, the Eurasian treecreeper is easily overlooked as it hops mouse-like up a vertical trunk, progressing in short hops, using its stiff tail and widely splayed feet as support. Nevertheless, it is not wary, and is largely indifferent to the presence of humans. It has a distinctive erratic and undulating flight, alternating fluttering butterfly-like wing beats with side-slips and tumbles. Migrating birds may fly by day or night, but the extent of movements is usually masked by resident populations. It is solitary in winter, but in cold weather up to a dozen or more birds will roost together in a suitable sheltered crevice. Conservation status This species has an extensive range of about 10 million km2 (3.8 million square miles). It has a large population, including an estimated 11–20 million individuals in Europe alone. Population trends have not been quantified, but the species is not believed to approach the thresholds for the population decline criterion of the IUCN Red List (declining more than 30% in ten years or three generations). For these reasons, the species is evaluated as Least Concern. It is common through much of its range, but in the northernmost areas it is rare, since it is vulnerable to hard winters, especially if its feeding is disrupted by an ice