(Orthonychidae)
Class: Aves
Order: Passeriformes
Suborder: Passeri (Oscines)
Family: Orthonychidae
Thumbnail description
Small, stocky ground birds with powerful legs and shafts of tail feathers extending as spines
Size
7.3–11.8 in (18.5–30 cm); 0.10–0.47 lb (47–213 g)
Number of genera, species
1 genus; 3 species
Habitat
Rainforest and contiguous thick, low secondary growth
Conservation status
Not threatened
Distribution
Eastern Australia and central ranges of New Guinea
Evolution and systematics
The taxonomic placement of these unusual birds was long problematic. Traditionally they were included with other ground-frequenting passerines of the Australian and New Guinean region, such as quail-thrushes and whipbirds. The DNA-DNA hybridization studies by Charles Sibley and Jon Ahlquist in 1980–90s demonstrated that logrunners were quite distinct from these and other passerine families. Since then they have been separated at family level, an action supported by subsequent research, within the Australo-Papuan corvine radiation. They comprise one of the older groups, with fossil species known from Miocene and Quaternary deposits in Australia.
The distribution of the species has attracted much attention. The southern species, the southern logrunner (Orthonyx temminckii) occurs through central eastern Australia, then apparently leapfrogs the larger, darker chowchilla (O. spaldingii) of northeastern Australia, to reappear in the central ranges of New Guinea. This unusual pattern was illuminated in 2001 by Leo Joseph and his colleagues, who showed that the New Guinea populations were specifically distinct from those in southeastern Australia; they thus take the name New Guinea logrunner (O. novaeguineae). It is not certain, however, to which of the Australian species it is most closely related.
Earlier names for the Australian species were the southern and northern logrunners for O. temminckii and O. spaldingii, respectively. When the New Guinea populations were considered to be conspecific with O. temminckii, the common name of the latter was deemed inappropriate and shortened to logrunner; the name for O. spaldingii was changed to chow-chilla, a rendering of its distinctive call. Now, with the logrunners split into two species, it seems appropriate to qualify the name of the Australian birds by reintroducing the traditional name, southern logrunner. The name logrunner is used collectively for the birds of this family.
The morphology of the hind limb and pelvis reflects the characteristic ground feeding method used by these birds. The femur has a distinctive hour-glass shape bestowed by the expansion of the distal end as a brace and the proximal end for muscle attachments. The pelvis is broad, with deep excavations for the powerful muscles that drive the legs.
Physical characteristics
Logrunners are stocky birds, with the chowchilla, the largest species, reaching a length of 12 in (30 cm); the other species are noticeably smaller (7.3–8.3 in; 18.5–21 cm). All have powerful legs and claws. The unspecialized bill is of moderate strength. Perhaps the most curious physical feature of these birds is the stiffened shafts of the 10 tail feathers, the tips of which protrude beyond the ends of the feathers as pliable spines. This led to the earlier name of "spine-tailed logrunner." While the chowchilla is simply colored with broad patches of unmarked black and white, and in one sex, orange, the other two species have much more complex patterns of brown, rufous, black, gray, and white. All three species have similar patterns of sexual dimorphism: males have white breasts, females orange ones.
Distribution
This family is found only in Australia and New Guinea. The southern logrunner is distributed along coastal areas and adjacent ranges in appropriate habitat from central eastern New South Wales north to southeastern Queensland. The chowchilla is restricted to the Atherton Tableland region in northeastern Australia, particularly above 1,475 ft (450 m). New Guinea birds occur along the central highlands in a zone 6,500–9,300 ft (1,980–2,840 m), in places above and below this. There are breaks in the distribution, some of which are real and others that may merely reflect our poor knowledge of this rare species.
Habitat
Logrunners are birds of the rainforest, although they will venture into contiguous habitats if the vegetation is sufficiently low and thick; this can include invasive, introduced plants.
Behavior
Logrunners live in permanent territories in pairs or small family parties. In 1999 Amy Jensen reported that these groups of 2–5 birds occupied home ranges (the areas in which they foraged) of 1.7–9.8 acres (0.7–4.0 ha), substantially larger than the space actually defended. Territorial defense is strong, birds announcing themselves to neighboring families with loud calls. For the first hour after dawn they call constantly before settling down to feed. They also break into short bouts of calling throughout the day, particularly during encounters with neighbors along a border, and have a concluding burst at dusk. Mike McGuire investigated the vocalizations of several parties of chowchillas. His 1999 study recorded vocabularies of often complex calls with differing local dialects between adjoining groups.
These birds can be quite shy, quickly fleeing into cover, often with a loud shriek, when startled. At other times, they can be remarkably tame, ignoring quiet observers while they search for food—even walking across a person's feet while the bird is foraging.
Feeding ecology and diet
The purpose of the spine-tipped tail and oddly shaped femur become apparent when logrunners feed. A feeding bird spreads its tail and rests the spine-like quills against the ground. To expose the soil, the bird rakes a foot through the leaf litter and fallen sticks, throwing the leg to the side, perpendicular to the body. Once the ground is sufficiently cleared to feed, the legs are used alternately to scratch the soil front to back in search of insects, larvae and other invertebrates that form the diet, balancing on one leg while at the same time using the tail as a supporting prop. Pivoting around the tail, logrunners produce distinctive small cleared patches about 8 in (20 cm) in diameter on the forest floor. A foraging bird spends a brief period scratching at the one spot before moving on to another a short distance away. Smaller ground-feeding birds, such as the yellow-throated scrubwren (Sericornis citreogularis) and eastern whipbird (Psophodes olivaceus), may attend foraging logrunners, picking up small invertebrates that are unearthed by the scratching.
Reproductive biology
Unlike many Australian passerines, southern logrunners concentrate much of their breeding in the winter. Starting in about April or June their nesting season continues through to August or September, sometimes as late as October. The female is responsible for building the nest and incubating the eggs, and she provides most of the care for the young.
The nest is a globular dome, usually placed on the ground but on occasion may be situated in low vines or on a fallen log or a stump. The female builds a platform up to 2 in (5 cm) of short, thick sticks. She adds curving sides until these meet and join at the top, finally capping this with dry leaves and green moss. This roof hangs over the side entrance, partially concealing it and keeping the interior of the nest dry, even in heavy downpours. The clutch characteristically comprises two eggs, which are large and white. Usually these hatch after a 21–25 day incubation period. The female has most of the responsibility for feeding the nestlings, but she is assisted by the male; he passes food to her, which she in turn gives to the young birds. The young remain in nest for 16–18 days. After fledging they are fed by both parents. Juveniles have a mottled breast, which on the subsequent moult acquires the color appropriate to the bird's sex.
The breeding biology of the chowchilla, which was long unknown, was revealed in 1997 by Cliff Frith and his associates. Most aspects are similar to those of the southern logrunner, with some important differences. Nesting can occur in any month of the year, peaking in July through December. The nest is the same shape but considerably larger. Only a single egg is laid. Both incubation and nestling periods are longer: 25 days, with 75% of eggs hatching, and 22–27 days, with 67% of young successfully leaving the nest. More than one male may bring food to the female, but males do not themselves feed the chick.
What is known of the breeding in New Guinea logrunners is similar, with records from March and November of nests with single eggs.
Conservation status
The clearance of rainforest has eliminated southern logrunners from parts of the range; however, this species appears capable of persisting in small, isolated patches of rainforest. A population persists to the south of the metropolis of Sydney, New South Wales, well separated from the northern section of its range, and a pair of birds was found in 5 acres (2 ha) of rainforest that had been long-isolated within a surrounding countryside of dairy land. The possibility that proliferating exotic plants, such as lantana and blackberry, in and around the rainforest might force this species from its habitat did not eventuate. The southern logrunner seems to have adapted well to thick stands of these plants, using their cover to colonize along watercourses and even moving away from rainforests into areas where these vigorously invading plants have made inroads into cleared land.
While clearing has undoubtedly reduced the habitat available to chowchillas, this species remains common in northeastern Australia. The New Guinea logrunner appears to be uncommon to rare, but this may be due in part to its shy nature and the remoteness of much of its range. Only in 1987 was it discovered at Tari Gap, central New Guinea, where it had long been thought to be absent.
Significance to humans
The restricted habitat and cryptic behavior of these interesting birds make them unfamiliar to most people. The name "chowchilla" is the name used by the Dyirbal Aboriginal people, itself derived from this bird's call.
Species accounts
Southern logrunnerNew Guinea logrunner
Chowchilla
Resources
Books:Coates, Brian J. The Birds of Papua New Guinea. Vol. 2, Passerines. Alderley: Dove Publications, 1993.
Higgins, P. J., and J. M. Peter, eds. Handbook of Australian, New Zealand and Antarctic Birds. Vol. 6, Pardalotes to Figbird. Melbourne: Oxford University Press, forthcoming.
Schodde, R., and I. J. Mason. The Directory of Australian Birds. Passerines. Collingwood: CSIRO Publishing, 1999.
Periodicals:Frith, C. B., D. W. Frith, and A. Jensen. "The Nesting Biology of the Chowchilla Orthonyx spaldingii (Orthonychidae)." Emu 97 (1997): 18–30.
Hindwood, K. A. "The Spine-tailed Log-runner (Orthonyx temminckii)." Emu 33 (1934): 257–67.
Jensen, A. "Home Ranges and Group-territoriality in Chowchillas Orthonyx spaldingii." Emu 99 (1999): 280–90.
Joseph, L., B. Slikas, D. Alpers, and R. Schodde. "Molecular Systematics and Phylogeography of New Guinean Logrunners (Orthonychidae)." Emu 101 (2001): 273–80.
McGuire, M. "Dialects of the Chowchilla Orthonyx spaldingii in Upland Rain Forest of North-eastern Australia." Emu 96 (1996): 174–80.
Organizations:Birds Australia. 415 Riversdale Road, Hawthorn East, Victoria 3123 Australia. Phone: +61 3 9882 2622. Fax: +61 3 98822677. E-mail: mail@birdsaustralia.com.au Web site:
[Article by: Walter E. Boles, PhD]
