Wednesday, March 14, 2012

Eurasian Treecreeper/ Træløber

Eurasian treecreeper

Certhia familiaris
The Eurasian Treecreeper or Common Treecreeper (Certhia familiaris) is a small, insignificant bird and has a curved bill, patterned brown upperparts, whitish underparts, a broad, white eye-stripe and long stiff tail feathers which help it creep up tree trunks. The spread of the treecreeper is the northern, eastern and central Europe and eastwards through Russia and Central Asia to the Pacific Coast and Japan. The treecreeper appears especially in hardwoods and parks, but also in older coniferus forests, the species is especially numerous in old nature-forest, where 20-40 couple can breed pr. km2. The treecreeper is relatively mobile and is found all over the Denmark, including most small islands. During the last decades of the 20th century it was during expansion, especially in the northern Jutland and upon the western Lolland. This might be connected to the mild winters of the 1990s and partly an ageing of the north Jutland forests, which made them more suitable for the treecreeper.

alder swamp
The Eurasian treecreeper can be most easily distinguished from the similar Short-toed treecreeper, which shares much of its European range, by its different song.The name refers to that it runs upon trees, where it is fishing insects from the furrowed bark with its small, curved beak. Unlike the nuthatch the treecreeper only runs upwards, when it seeks food. It is almost identically in appeareance with the short-toed treecreeper, which also breeds in Denmark, but the short-toed treecreeper is not as common, and it's mostly spread in the southern part of the country. The two species have very similar requirements for habitats, in spring there are sometimes fierce territorial battles between them. In the field they are best separated by their voices. The treecreeper's song is a light strophe in a falling pitch with an abrupt rise to finish, while the call is weak, uniform strophes in a high pitch.

The treecreeper is a strejf-fugl which means that it is roaming inside its area without being a migration bird. It stays in Denmark in winter, where it is often seen in mixed flocks with tits. Birds from northern populations are seen in migrations, especially on the island Bornholm, in spring and autumn. In cold winters the treecreepers often overnight close together to keep the warmth, and in very hard winters the mortality is high. The overwintering means that the treecreeper already in the end of February starts the breeding-activity, and the singing is at its highest in the middle of March. It begins to build the nest in late April, and it is typically placed in holes in old trees or under large pieces of loose bark.

alder swamp
The food of the treecreeper is insects, insect-larvaes and spiders, which it finds under the bark of the trees. Since the density of insects is highest in old trees with a knotty, rough bark, the treecreeper especially seeks its food in trees like oak, ash, fir and alder. It has a very characteristic way of doing this. It starts from the bottom of the tree and moves upwards in a spiral around the stem, while it's moving its head from side to side to find insects. When it has reached the top, it flies down again and starts the research in a new tree.

Breeding couple in Denmark in 2000: 15.000-25.000

Source: Natur og Fugle, Dansk Ornitologisk Forening 

photo Klostermølle 10. March 2012: grethe bachmann


Out on the prairie said...

Have one here,certhia americana, with a shorter bill.It is a fun bird to watch and listen to.

Thyra said...

Hej Steve, yes, I also like those little birds in spring. You've got many fine photos of birds where you live. I think they are often difficult to get close to, but this one just sat quite still. I don't know if it was half-sleeping or stiff with fright? ´) And it is fantastic how its colours blend with the stem of the tree.
Have a good day !
Grethe ´)