Tree Creepers are small, mostly brown birds that are usually seen climbing steadily up the trunk of a tree and along its branches, and then planning down to the base of another tree to repeat the process. They have long toes with deeply curved claws for climbing and a slightly down-curved bill for probing into crevices and under flakes of bark in search of insects. Apart from these adaptations to their niche, however, the members of the three families of treecreepers have little in common.
Even their climbing techniques differ. In the Holarctictreecreepers the feet are held parallel and are moved simultaneously, whereas in the Australasian tree creepers, one foot is always held in front of the other and the lower foots brought up to the level of the upper before the latter is moved higher. Moreover, most species of Australasian tree creepers spend much time on the ground.
The five species of Holarctic treecreepers belonging to the genus Cathie are unique among tree creepers in possessing pointed tail feathers with stiffened shafts, which aroused as a prop when climbing. This adaptation is also seen in the unrelated woodpeckers and woodcreepers. The five Certhiaspecies are very similar in appearance and habits, being mainly solitary. The circum-polar Common tree creeper, known as the Brown creeper in America, overlaps the Range of all four of the other species to some extent.
In Britain, where it is the only treecreeper, this species inhabits open deciduous woodlands, but in Europe, this habitat is occupied by the Short-toed treecreeper, and the Common is confined to coniferous forests. Four species occur in the Himalayas up to the timberline (about 3, 5 rooms, 5ooft), all moving down to the foothills and adjacent plains during winter. The Himalayan tree creeper favors conifers and avoids pure oak forest, where it is replaced by the Brown-throated treecreeper. The Stoliczka’s tree creeper haste the most restricted distribution of all, but it’s not known how this bird differs from the others in its habitat or niche requirements.
Although the Spotted creeper is included in the Holarctic tree creepers it lacks the modified tail of the main genus Cathie and differs markedly from all other treecreepers in its nest, which is built on a horizontal branch usually in a fork. It is beautifully camouflaged, being decorated externally with spiders’ egg bags, lichen, and caterpillar frays (excrement). This peculiarity sag-gests that it may have closer relatives than other no-climbing families.
Similarly, though once considered allied to the Australasian tree creepers, the Philippine creepers lack the sexual differences and modifications of the foot of the latter and may instead represent a branch of the diverse Asian babblers (Timeline). Little is known about these birds. They reputedly gather at times to visit flowering plants in open areas but their tongue is not particularly specialized for nectar-feeding. Of’ the two Philippine creepers the larger Plain-headed creeper prefers the higher montane forest regions, while the Stripe-headed deeper occupies lower areas.
The six species of Australasian tree-creepers are all found on the Australian mainland, but one also occurs in New Guinea. They overlap little in their distribution except in southeastern Australia, where the White-throated often coexists with the Red-browed in eucalypt forests, and with the Brown in woodlands and partly cleared areas. The larger Brown is often found on the ground but the other two are similar in size and live almost entirely in trees. However, the White-throated uses rough-barked trees more than the Red-browed, preferring the fibrous bark of the trunk, while the latter concentrates on the smooth branches of such trees.
The White-throated tree creeper is the only species that occurs in rainforests and possibly had a different ancestor to the other Australasian tree creepers. It differs in many respects, including patterns of sexual differences. Juvenile plumage and egg color-action. In the White-throated, females have orange spots on the cheek while females of the other species are characterized by rufous stripes on the chest.
Juvenile White-throated tree creepers have a whitish streak on the scapular feathers (above the shoulders) and a bright chestnut patch on the rump (in females), features lacking in the other species. In contrast with the other species, the White-throated has relatively unmarked eggs, and only the female builds the nest. It has a much longer incubation period, a special territorial display, and calls specific to each sex. Moreover, it roosts externally whereas the other species generally sleep inside hollow spouts.
Social organization varies greatly among the Australasian tree creepers. The White-throated breed in pairs but is normally soli-tarry during the no-breeding season. By con-trust, the Red-browed and Browntreecreepers live in pairs or groups of up to six. These groups usually consist of the breeding pair and their male offspring, females tending to disperse in their first year. Both species breed communally, nonbreeding birds feeding the incubating female and young. In the Brown, however, birds sometimes attend two nests in different territories contemporaneously.
This unique behavior results from, firstly, some birds continuing to attend nests in their natal territory even after they have become breeders with their separate territory, and secondly somenonbreeders attending the young of their brothers or stepbrothers, as well as their father. The parents benefit from this “help “from these extra attendants but the latter may also benefit in the future from the help of the young they attend.