The Eurasian treecreeper is an old-growth forest passerine preferring forests of over 100 years old. The species is altricial and the chicks fledge at an age of 14–16 days. Clutch size varies from 3 to 8 (5.5 ± 0.9 eggs (mean ± s.d). The treecreeper specializes in searching for invertebrates on tree trunks. Nests are placed behind the flaps of loose bark or in the crevices of tree trunks, but females also accept specially designed nest-boxes. The treecreeper specializes in searching for invertebrates, especially spiders, which constitutes 65% of their nestling food mass, on tree trunks. Evidence suggests that treecreepers may maximize the number of offspring per breeding attempt by adjusting the sex ratio of their progeny in relation to habitat quality. This can be assumed to be a reasonable strategy for a short-lived passerine species characterized by a low number of subsequent breeding attempts. Habitat quality, in general, may play an important role in determining essential life-history traits in forest-dwelling species (Suorsa et al. 2003)
In forest-interior passerines, the loss of forest area may lead to chronic food shortage and consequently lowered breeding performance. The treecreeper is explicitly dependent on forested areas since it forages for invertebrates (primarily spiders) on tree trunks, the number of which may be lower in small forest fragments than in large fragments. In addition to the lower number of food patches (trunks), the invertebrate densities may be adversely affected by edge effects especially in small forest patches characterized by a high edge–area ratio. For example, surface-dwelling invertebrates are prone to desiccation, which may decrease their survival in edge habitat, characterized by a warmer and drier climate, as compared to that in forest interiors (Suorsa et al. 2004).
Predators of treecreeper nests and young include the Great Spotted Woodpecker, Red Squirrel, and small mustelids, and predation is about three times higher in fragmented landscapes than in solid blocks of woodland (32.4% against 12.0% in less fragmented woodlands). The predation rate increases with the amount of forest edge close to a nest site, and also the presence of nearby agricultural land, in both cases probably because of a higher degree of mustelid predation. This species is parasitized in the nest by the moorhen flea, (Dasypsyllus gallinulae). The juvenile survival rate of this species is unknown, but 47.7% of adults survive each year. The typical lifespan is two years, but the maximum recorded age is eight years and ten months (Huhta et al. 2004).
Reference List
- Huhta.E., Aho.T., Jantti.A., Suorsa.P., Kuitunen.M., Nikula.A., & Hakkarainen.H., (2004) Forest Fragmentation Increases Nest Predation in the Eurasian Treecreeper. Conservation Biology, 18, 148-155.
- Suorsa.P., Helle.H., Huhta.E., Jäntti.A., Nikula.A., & Hakkarainen.H., (2003) Forest fragmentation is associated with primary brood sex ratio in the treecreeper (Certhia familiaris). Proceedings of the Royal Society of London for Biological Sciences, 270, 2215-2222.
- Suorsa.P., Helle.H., Koivunen.V., Huhta.E., Nikula.A., & Hakkarainen.H., (2004) Effects of forest patch size on physiological stress and immunocompetence in an area-sensitive passerine, the Eurasian treecreeper (Certhia familiaris). Proceedings of the Royal Society of London for Biological Sciences, 271, 435-440.
