The Eurasian treecreeper breeds from the age of one year, nesting in tree crevices or behind bark flakes.[1] Where present, the introduced North American giant sequoia is a favourite nesting tree, since a nest cavity can be easily hollowed out in its soft bark.[9] Crevices in buildings or walls are sometimes used, and artificial nest boxes or flaps may be preferred in coniferous woodland.[3] The nest has a base of twigs, pine needles, grass or bark, and a lining of finer material such as feathers, wool, moss, lichen or spider web.