Creeper

Creeper Birds or Treecreepers is the term that is used to define any of the various small birds that can be found creeping along the tree trunks or rock surfaces while they move about for feeding. These treecreepers belong to the family, Certhiidae, consisting of the small passerine birds. Creeper birds are widely distributed in the wooded regions of the Northern Hemisphere and sub-Saharan Africa. This family of Creeper (Certhiidae) includes ten species belonging to the two specific genera, i.e., Certhia and Salpornis. They all have a dull-coloured plumage and as their name implies, they are often found climbing over the tree surfaces in search of food.

Some of the common Creeper birds or songbirds, belonging to the order Passeriformes are - Brown Creepers (Certhia americana) and Indian spotted creeper (Salpornis spilonotus). 

In this article, we have discussed the distribution and habitat of the creeper. Students who are wondering about what is the creeper bird characteristics and classification can refer to this page for the answers. Information about the Brown Creeper as well as the Indian Spotted Creeper has also been provided here.

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Taxonomy of Creeper 

The Creepers belong to the family Certhiidae which consist of two subfamilies, Certhiidae and Salpornithinae, each with one genus. The distinctive anatomical and behavioural characteristics of these sub-families have been discussed in this article. One can refer to these characteristics to understand what are creepers and their classification.

The superfamily, Certhiidae, was formed on the basis of phylogenetic studies using mitochondrial and nuclear DNA. It was initially created to group together a clade of four families that were removed from a larger grouping of passerine birds, i.e., the Sylvioidea. The fossil record of this group was discovered and reported to be a foot bone of an early Miocene bird from Bavaria. This bird has been identified as an extinct representative of the climbing Certhioidea family, which is a clade comprising the treecreepers, wallcreeper and nuthatches. It has been later scientifically named as Certhiops rummeli.

The genus Certhia belonging to the Subfamily Certhiinae includes the typical treecreepers. It consists of seven Creeper species that are found in Europe and Asia. It also includes the brown creeper species which is found abundantly in North America. The genus name Certhia is derived from the Ancient Greek word ‘kerthios’, which meant a small tree-dwelling bird as described by Aristotle and others.

On the other hand, the Subfamily Salpornithinae includes the genus Salpornis consisting of only two Creeper species, i.e., the Indian spotted creeper and African spotted creeper.

The Australian treecreepers (Family - Climacteridae) and the Philippine creepers (Family - Rhabdornithidae) are two other small bird families with treecreeper or creeper in their name but are not closely related to each other. The wallcreeper, which today is considered to be related to the nuthatches, was once originally described in the family Certhiidae. The woodcreepers belonging to the subfamily Dendrocolaptinae also have a similar name.

Given below are the 9 common Creeper Species found under the Genus Certhia are as follows:

• Eurasian treecreeper or common treecreeper (Certhia familiaris)

• Hodgson's treecreeper (Certhia hodgsoni)

• Brown creeper (Certhia americana)

• Short-toed treecreeper (Certhia brachydactyla)

• Bar-tailed treecreeper or Himalayan treecreeper (Certhia himalayana)

• Sichuan treecreeper (Certhia tianquanensis)

• Rusty-flanked treecreeper or Nepal treecreeper (Certhia nipalensis)

• Sikkim treecreeper or brown-throated treecreeper (Certhia discolor)

• Hume's treecreeper (Certhia manipurensis)

Indian spotted creeper (Salpornis spilonotus) and African spotted creeper (Salpornis salvadori) are two species of creepers included under the Genus Salpornis. 

General Characteristics of Creeper Bird

Some of the general characteristics of the Creeper bird species are as follows:

1. The treecreepers generally have a length ranging from 12 to 18 centimetres. 

2. Their bills are long and gently curved downwards which are used for probing bark for insects and spiders. 

3. The creepers are often found to climb up tree trunks by hopping with their feet together in a helical path. They have long toes with strongly curved claws which are used for gripping. 

4. The treecreepers belonging to the genus Certhia have longer and stiffened tails that are used as a prop while climbing, but those found in the spotted creepers are shorter and not stiffened. 

5. These birds are often regarded as singing birds and are known for their thin and high-pitched calls.

Creeper - Distribution and Habitat

Most of the treecreeper species are found to inhabit the Palearctic and Indomalayan realms, ranging from Western Europe to Japan as well as India. Most of the northerly species are partly migratory, and those found in warmer climates are thought to be resident, although information is lacking for many species. One species of creeper, i.e. Brown creeper (Certhia americana) is found in North America from Alaska to Nicaragua. The Indian spotted creeper (Salpornis spilonotus) and African spotted creeper (Salpornis salvadori)  have a discontinuous distribution in India and sub-Saharan Africa respectively. All species of treecreeper are found commonly in forest and woodland habitats. 

Behaviour and Ecology of Creepers

Treecreepers are mostly found to be unobtrusive and indifferent to humans. They occur as singles or in pairs, sometimes in small family groups after fledging. Communal roosting has been observed in three species (and may occur in more), with as many as 20 birds sharing a roosting hole in order to conserve warmth.

Treecreepers are found foraging at the trunks of large trees. They move up the trunk in a progression of small hops. They fly to the lowest level of a tree, then climb in a spiral manner in search of prey. Most of their diet consists of small invertebrates, which include insects, their larvae, spiders, and pseudoscorpions. In hard times seeds and fruits may be taken, and a few species will also visit bird feeders. Species in both genera have been recorded joining mixed-species feeding flocks. 

The creeper bird species are also monogamous and territorial. The eggs and nesting patterns seem to vary between both genera.  Those belonging to Genus Certhia, usually nest in a gap between the tree bark and the tree, whereas the species of Genus Salpornis i.e., the spotted creepers make their nest in the fork of a branch. The Incubation period for both of the genera lasts 14 to 15 days, and starts to fledge after 15 to 16 days. 

Brown Creepers

The brown creepers also commonly known as the American treecreepers  (Certhia americana) are the small songbirds belonging to the treecreeper family Certhiidae and are found mostly in North American. They have brown upper parts with some light spotting that resembles a piece of tree bark, with white underparts. They have a long thin bill that is curved slightly downwards along with a long stiff tail which is used for support as the bird creeps upwards. The male creeper has a slightly larger bill than the female. Relatively, brown creepers are smaller than white-breasted nuthatches but larger than golden-crowned kinglets. They have a body length ranging from 4.7 inches - 5.5 inches (12 cm - 14 cm) with an average weight between 5g -10g. They have a wingspan of 6.7 inches - 7.9 inches (17 cm - 20 cm).

The brown creepers are known for their single and very high pitched calls. These calls are often short, insistent and thus they have also been given the name of singing birds. The song often has a cadence like willow-wee or with notes similar to the calls.

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Distribution and habitat of Brown Creepers

This species of creeper birds are found to inhabit mature forests, especially conifers, in Canada, Alaska and the northeastern and western United States. It has also been found that these birds reside permanently in all of their range. Although many northern birds migrate farther south to the United States. Brown creeper is also vagrant to Bermuda and Central America's mountains in Guatemala, Honduras and the northern cordillera of El Salvador. They have also experienced a 1.5% yearly population increase throughout the northeastern and northwestern (Pacific coast) regions of its range since the year 1966.

Regarded as a migratory bird species found in the northern range, the brown creeper is a conceivable vagrant to western Europe. However, they have intermediate characteristics of both common treecreeper and short-toed treecreeper, and has sometimes been considered a subspecies of the common treecreeper in the past, although its closest relative seems to be the short-toed treecreeper.  Since the two European treecreepers are themselves among the most difficult species on that continent to distinguish from each other, a brown creeper would probably not even be suspected, other than on a treeless western island, and would be difficult to verify even then.

Brown Creepers prefer mature, moist, coniferous forests or mixed coniferous/deciduous forests. They are found in drier forests as well, including Engelmann Spruce and larch forest in eastern Washington. They generally avoid the rainforest of the outer coast. While they generally nest in hardwoods, conifers are preferred for foraging.

Behaviour

They are often found foraging on the tree trunks and branches, usually spiralling upwards from the bottom of a tree trunk, and then flying down to the bottom of another tree. These birds creep in a slow manner with their body flattened against the bark, along with probing their beak against it to prey on insects. They will rarely feed on the ground. They mainly eat small arthropods found in the bark, but sometimes they will eat seeds in winter.

Breeding Process

Breeding season for the brown creepers starts in the month of April. In this season, the female creeper makes a partial cup nest either under a piece of bark partially detached from the tree or in a tree cavity. They can lay around 3 to 7 eggs, and the incubation period lasts approximately two weeks. Both of the creeper parents are found to help feed the chicks.

Indian Spotted Creeper 

The Indian spotted creeper (Salpornis spilonota) belonging to the genus Salpornis is a small passerine bird placed along with the treecreeper family Certhiidae. It belongs to the subfamily Salpornithinae and has a marbled black and white plumage that makes it difficult to spot while foraging on the trunks of dark, deeply fissured trees. They are often found preying on insects using their curved bill. They are not migratory birds and are found inhabiting patchily distributed localities mainly in the dry scrub and open deciduous forests of northern and central peninsular India. Their inclusion along with the treecreepers is not certain and some studies find them more closely related to the nuthatches while others suggest a close relation to the wallcreeper. They lack the stiff tail feathers of treecreepers and do not use their tail for supporting them while creeping vertically along tree trunks.

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The Indian spotted creepers are grey and white spotted birds having a barred plumage. They can weigh up to 16 grams, which is twice as much as treecreepers and have a body length up to 15 cm. They have a thin pointed bill that is curved downwards and is a bit longer than the head. It is used to extricate insects from bark, but these birds lack the stiff tail feathers to prop themselves on the vertical surface of tree trunks. They instead have a whitish supercilium contrasting with a dark eye stripe and white on the throat. The wing is long and pointed with a highly reduced first primary feather. 

Distribution of Indian Spotted Creeper

These species of Indian spotted creepers are found in locations scattered around parts of Rajasthan, Gujarat, Haryana, Uttar Pradesh, Central India, Orissa and Andhra Pradesh. Initially, the slightly paler plumaged population of these creepers were found in the arid zone of the Aravalli hills and were considered to be a subspecies Rajputanae by Richard Meinertzhagen (and his wife) but later they were treated as part of a single population and combined into a single subspecies. The Indian creepers are found mainly in habitats having trees with deeply fissured bark including those of Acacia, Diospyros, Tectona and mango.