Australian treecreepers are usually found in pairs, family groups, or alone. When they are found in pairs, or family groups, territorial defenses are more obvious, such as chasing and calling. Otherwise, the birds tend to be sedentary, stay in one place. Only in some young birds does any migration, travel, occur, and then it is only within several miles or kilometers.
The Great Australasian Radiation refers to the period of time when many different birds evolved across Australia and Asia—the birds evolved in isolation for eons. Australian treecreepers are part of that radiation. Data has indicated that they are related to lyrebirds, scrub-birds, and bowerbirds. The birds' behavior had originally placed them near the northern treecreepers, spotted creepers of Africa and India, and Philippine creepers. But they are not related to any of these birds. Their tree-climbing is an example of convergent evolution, where species develop similar characteristics although they are not related.
Most species have a voice that consists of shrill, high-pitched whistles. Their display includes tail clicking and flicking.
Some species breed in pairs. Those include the white-throated treecreeper in Australia and New Guinea. Most are cooperative breeders, where young males from previous breedings help care for and protect the current chicks. Those species that breed cooperatively include the red-browed treecreeper, the black-tailed treecreeper, the brown treecreeper, and the rufous treecreeper. Neighboring groups of treecreepers often have close relationships with each other, with males going only one or two territories away from their homes to live. The breeding season is from August to January, with many attempts to breed. It is not uncommon for Australian treecreepers to have two broods a year. The nests are built deep into tree hollows, or sometimes in a hollow log or other cavity. Nests are made of grasses, plant down, soft bark, and animal fur. The female is known to sweep snakeskin, insect wings, and even plastic around the entrance to the nest. One or more males assist the female in incubation, the process of sitting on eggs to provide warmth for development. Eggs are found in clutches of two or three and are white to pinkish in color with brown markings. The incubation takes place over fourteen to twenty-four days, with fledging at twenty-five to twenty-seven days.
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