Certhia familiaris
Eurasian tree-creeper
(Also: Eurasian treecreeper)

Eurasian treecreepers (Certhia familiaris) reside within the Palearctic region. They are found throughout most of Europe as well as select regions of Asia. Their range stretches from Germany and Norway westward to the Pacific coast of Russia and Korea. These birds also reside in the United Kingdom and Japan. Eurasian treecreepers are found as far south as Turkey and Iran and as far north as Norway, Sweden and Russia. ("IUCN Red List of Threatened Species", 2009)

Eurasian treecreepers inhabit deciduous and coniferous woodlands but primarily breed in pine or spruce forests. These birds have three times higher breeding densities in old-growth forests than in managed forests. In general, treecreepers are poor fliers and are better suited for climbing vertically up tree trunks. Therefore they are abundant in mature forests or parks with high densities of large, mature trees. These birds inhabit higher elevations of 400 to 2135 m above sea level. ("BirdFacts", 2011; Dittmann, et al., 2009; Jäntti, et al., 2007a)

Eurasian treecreepers are 12 to 15 cm in length and weigh an average of 10 g. Male and female treecreepers are similar in appearance. The head and upper body are mottled with black, dark brown, tan, and white. Their brown upper bodies contrast sharply with their unmarked, white throats, bellies and under tail coverts. They also feature broad, white supercilia and thin, decurved bills. Treecreepers have long, stiff tail feathers that support them while climbing and foraging on trees. ("BirdFacts", 2011; Beletsky, 2006; Dittmann, et al., 2009; Dunning, 2009; Norberg, 1986)

Eurasian treecreepers are monogamous. Male treecreepers sing to attract female partners. These calls are a sequence of shrill and high-pitched sounds. It is unknown if pair-bonds last longer than one season. (Jantti, 2005; Jäntti, et al., 2007b)

For Eurasian treecreepers, the breeding season occurs between March and late June. Eurasian treecreepers are known to make cryptic nests in tree crevices and behind pieces of loose bark. Their nests are typically made using twigs, vegetation, cocoon parts, spider egg cases, bark, fibers, leaves, mosses, and feathers. They produce two broods per breeding season, with each clutch consisting of 1 to 6 eggs that weigh approximately 1.2 g and measure 16 by 12 mm. Eggs are white with pink or reddish brown spots. Female treecreepers incubate the eggs until they hatch after 13 to 17 days. After hatching, the chicks develop in the nest for 13 to 18 days before they fledge. Time to independence is currently unknown. Juvenile Eurasian treecreepers are able to reproduce at 1 year old. ("BirdFacts", 2011; Burton, 2003; Jäntti, et al., 2007b)

Eurasian treecreepers are monogamous. Both parents care for the offspring and defend the nest during the first brood, but in most cases only the female defends the second brood. The females incubate the eggs. Once hatched, the altricial young are helpless on their own and have only a little bit of down on their heads. Only female treecreepers brood the hatchlings. Male and female treecreepers take turns feeding their young, but the female parents feed the nestlings more than the males. Males invest most of their time in defending the nest and surrounding territory from rival males and predators. Male and female parents take care of the chicks for 13 to 18 more days until fledging. (Beletsky, 2006; Jantti, 2005; Jäntti, et al., 2007b)

The oldest known wild Eurasian treecreeper lived 8 years and 2 months, but the average life expectancy is 2 years. (Fransson, et al., 2010)

Eurasian treecreepers are non-migratory birds that reside in the same general region throughout the year. They are diurnal birds that are active during the day and often form communal roosts at night. Communal roosts may consist of up to 15 treecreepers and most often occur on nights with low temperatures.

Like all treecreepers, these birds have a specialized foraging behavior of "creeping" vertically up tree trunks. Their stiff tail feathers are adapted to support their body weight as they climb vertically, and their decurved bills serve to reach invertebrates under tree bark. Once an individual has reached the top of a tree, it will swoop downward to begin foraging at the base of a new tree. Eurasian treecreepers compete with red wood ants for food. As a result, treecreepers spend less time foraging on tree trunks with ants present because the amount of ants has a negative effect on the number of invertebrates the birds can feed on. (Aho, et al., 1997; Beletsky, 2006; Jantti, 2005; Norberg, 1986)

Currently there are no estimates of Eurasian treecreeper home range.

Male Eurasian treecreepers are known to sing complete and incomplete songs. These incomplete songs, also known as mixed songs, contain a mix of both Eurasian treecreeper and short-toed treecreeper songs and occur where the two species overlap. This occurs when the song is being transmitted from parent to offspring. If the offspring hears another species’ song during song transmission, it will learn a mixed song due to error in copying. The purpose of singing among male treecreepers is primarily to deter rival males from entering the territory during breeding season.

Eurasian treecreepers exhibit low song variation and complexity. Some male individuals sing shortened and mixed variants of the same song type. There is no specific song repertoire among treecreepers.

Like most birds, Eurasian treecreepers use sight, sound, touch, smell and taste to perceive their environment. (Osiejuk and Kuczynski, 2003; Thielcke, 1986)

Eurasian treecreepers forage on insects, spiders, and other arthropods. Eurasian treecreepers' slim curved bills allow them to reach insects hidden behind the crevices in tree trunks.

In the winter when food is scarce, Eurasian treecreepers search for food on the ground and incorporate seeds into their diets. (Aho, et al., 1997; Beletsky, 2006)

Eurasian treecreepers have cryptic coloration that help them blend in with tree trunks to avoid being spotted by predators. Treecreepers' nests also camouflage with the habitat. Potential nest predators include great spotted woodpeckers, least weasels, and stoats. Breeding treecreepers will use a "tjii"-alarm call, a high-pitched, narrow frequency call to silence their nestlings first before actively defending the nest. The call is difficult for predators to detect and serves to avoid alerting the predators of the nest’s location. ("creeper", 2011; Jäntti, et al., 2007b)

Eurasian treecreepers feed on insect and arthropod populations, thereby reducing the population of arboreal pests. When these birds incorporate seeds into their diets during winter, they may also serve as seed dispersers. (Aho, et al., 1997; Aho, et al., 1999)

Eurasian treecreepers likely help humans, specifically the timber industry, by controlling populations of wood-boring insects. (Jäntti, et al., 2007a)

There are no known adverse affects of Eurasian treecreepers on humans.

Currently Eurasian treecreepers are abundant and not considered a vulnerable species. However, they are extremely sensitive to forest fragmentation because they rely on mature forests for foraging and breeding. Deforestation also alters the birds' vegetation and climate conditions. ("IUCN Red List of Threatened Species", 2009; Jäntti, et al., 2007a)