VOL. 9 (3) SEPTEMBER 1981 69 Observations on the Red-necked Crake Rallina tricolor By IAN J. MASON*, H. B. GILL* and J. H. YOUNGt Introduction There is little known about the Red-necked Crake Rallina tricolor because of its shy, retiring habits and its crepuscular and nocturnal behaviour. This paper records new field observations by H. B. G. and J. H. Y., a study of museum material by I. J. M., and a review of the literature. · The scientific and English names used in the text are based on Olson (1973) and the Royal Australasian Ornithological Union (1978), respec­ tively. Distribution The Red-necked Crake is found in north-eastern Queensland, New Guinea and offshore island chains (Waigeu, Misool, Aru Islands), the Bismarck Archipelago and the Lesser Sundas (Damar, Tanimbars). In New Guinea, the species commonly inhabits lowland swamp forests and marshes. It may penetrate primary rainforest to 1500 m along the edges of creeks: Diamond (1972) records a specimen from Karimui at 1310 m in the Eastern Highlands, and in the Australian National Wildlife Collection, Canberra, there are chicks from Lake Kutubu (670 m) and eggs from Wagau, Herzog Mountains (1370 m). At these higher altitudes its distribution - but not necessarily its habitat- may overlap with that of the mountain-inhabiting Forbe's Chestnut Rail Canirallus forbesi (cf. Olson 1973, p. 392). Within Australia, the Red-necked Crake is an abundant resident in coastal north-eastern Queensland and may comprise two separate popu­ lations: Torres Strait Islands south to Mcllwraith Range, and from Cooktown south to Ingham and coastal offshore islands (i.e. Hinchin­ brook, Palm and South Barnard Islands) - see map. Occasionally it is recorded from the southern ranges e.g. Atherton Tableland. There are no records between the Mcllwraith Range and Cooktown (Endeavour River), an area of unsuitable tropical savannah woodland. A specimen was collected by J. T. Cockerell allegedly from Port Denison (=Bowen). The northern population inhabits thickets of vine and monsoon scrub and rainforest, the southern population inhabits dense rainforest. In both areas the birds are usually found in the vicinity of permanent creeks. *Division of Wildlife Research, C.S.I.R.O., P.O. Box 84, Lyneham, A.C.T. 2602. tPalm Cove, Captain Cook Highway, Cairns, Queensland 4871. AUSTRALIAN 70 MASON, GILL & YOUNG BIRD WATCHER Throughout its range it appears to be separated from potential eco­ logical competitors by habitat: the Buff-banded Rail Rallus philippensis mostly inhabits swamps and wet grasslands; Lewin's Rail Rallus pectoralis, which may extend as far north as Cairns, could overlap near creek courses, but it also utilizes a wider range of habitats. Similarly, the Bush-hen Gallinula olivacea, which co-exists with the Red-necked Crake, frequents grasslands and marshes. When any of the above species come into contact, it is possible that they utilize different food sources as do the sympatric Sora Porzana carolina and Virginia Rail Rallus limicola in North America (Horak 1970). Description of Age Classes Adults (Australian material). Males and females combined: total length 260-290 mm; wing span c. 360-440 mm; weight 166-215 g. Dorsal surface: crown, nape and mantle chestnut; back, scapulars and wing coverts medium to dark olive brown (slate wash to mantle), rump and tail browner; flight feathers somewhat browner than back, with three- sometimes four- whitish bars on the inner vanes (occasional obscure bars to outer webs of primaries). Ventral surface: sides of face, throat and breast chestnut (lighter to whitish on the throat); belly, abdomen, thighs and uppertail coverts greyer brown than dorsum; central belly, abdomen, thighs and vent variably barred cream (cinnamon washed, especially to vent); underwing coverts and flight feathers dull black barred white as on dorsal surface but more clear cut (white barring washed cinnamon on lesser coverts); tail grey brown. Iris orange-scarlet to scarlet. The irides showing no obvious outward signs of specialization for nocturnal activity. Bill colour variable, dull green-yellow to olive green, at times yellower on the cutting edge and lower mandible (it is not known whether there is any pigment change in relation to breeding, although the bill colour has been noted as bright fluorescent green during this period); inside bill green; tarsus and toes dull greenish yellow to light olive; claws light brown. In a number of specimens the barring to the belly, abdomen, thighs and vent varied from distinct to indistinct or absent (cf. Gyldenstolpe 1955). museum material is scanty and mostly poorly documented it is impossible to ascertain whether these differences are due to age or individual variation. Females average slightly smaller and marginally paler and may have relatively shorter bills than males (vide Geographical Variation). Austra­ lian museum specimens examined from Australia revealed an unusually high proportion of males. Presumably this is due to sampling bias as the sex ratio of Mayr's (1949) New Guinea sample was more even. Chicks. Down silky black. Iris brown; eye ring pale grey; bill black; inside bill pale fleshy pink; tarsus, toes and claws flesh grey to brown. AUSTRALIAN 72 MASON, GILL & YOUNG BIRD WATCHER Descriptions of the immature and sub-adult plumages are based on the only two skins of young Red-necked Crakes in Australian museum collections. (Mathews (1911) and North (1913) have also described birds in similar plumages.) Immature (AM 0.18443). Dorsal surface mid brown-grey, lighter on the crown, darker towards rump. F light feathers are dark brown, barred white. Throat whitish, rest of ventral surface plain light to mid grey­ brown, rustier on vent. Sub-adult (AM B.4509). Colouration approaches that of adults in that the dorsal surface is of the same tone but lighter, including rump and tail; crown, nape and mantle dull chestnut and washed with greyer tones. Upper breast dull brownish (paler on throat); belly and abdomen greyish brown with indistinct cream barring only to abdomen and vent (latter bars reduced and tinted with a cinnamon wash). Iris reddish brown; bill olive-brown; tarsus and toes greenish olive. Geographical Variation Ripley (1977) placed the Australian populations of the Red-necked Crake with nominate tricolor from New Guinea and its western satellite islands. However, variation within this subspecies may warrant further investigation. The observations below are based on the limited material available: New Guinea: Ambunti (East Sepik Province), Vanapa River (Central Province), 2 males: wing 154, 143; tail 71 , 63; tarsus 54, 48; exposed culmen 34, 31 mm; bill/wing ratio 0.23, 0.20 respectively. Crown, mantle and breast is a deep chestnut; rest of dorsal surface mid to dark slate grey; belly and abdomen similar in tone though lighter. Mayr (1949) and Ripley (1977) state that there is considerable variability within plumage tones and size. General plumage varying from slate-grey to brownish olive, and size decreasing clinally within New Guinea from west to east, the smallest birds being found in the Fly River region. Within this region Mayr's (Joe. cit. p. 14) measurements are comparable to those of ours from Cape York Peninsula. Australia: Cape York Peninsula ( = Torres Strait Islands-Mcllwraith Range) and north Queensland ( = Cooktown-Ingham) are similar in plum­ age but differ from the two New Guinea birds in having lighter tones to the areas of chestnut, and an olive-brown, not slate-grey dorsal and ventral plumage (vide Description of Age Classes). Mayr (loc. cit.) com­ ments that the Fly River birds immediately opposite to those of Cape York Peninsula average more slate-grey. However, there is one specimen in the Queensland Museum indistinguishable from the New Guinea material in plumage. Cape York Peninsula (6 males, 2 females): wing 142.3 + or - 2.1, 140; tail 66.7 + or - 5.7, 60.5; tarsus 46.3 + or - 2.2, 45.5; exposed culmen 27.5 + or - 1.5, 25.5; bill/ wing ratio 0.19, 0.19. North Queens­ land (6 males, 2 females): wing 149 + or - 4.2, 150; tail 70.3 + or - 3.0, 69.5; tarsus 45.2 + or - 2.1, 43; exposed culmen 27.0 + or - 0.6, VOL. 9 (3) SEPTEMBER 1981 Observations on the Red-necked Crake 73 Known distribution of the Red-necked Crake Rallina tricolor in Australia. Dots indicate recorded observations and specimens. AUSTRALIAN 74 MASON, GILL & YOUNG BIRD WATCHER 25; bill / wing ratio 0.18, 0.16. (All measurements in millimetres and are me~ns + or - s.d.) Cape York Peninsula specimens are smaller in wing than those from north Queensland. In view of Mayr's (1949) and Ripley's (1977) comments this may be simply clinal (Bergmann's Rule) but on the other hand, the lack of suitable habitat between these two populations and the probable sedentary nature of this species, may indicate sub­ speciation. General Behaviour Red-necked Crakes are very rarely seen by day, which raises the question of where they roost. On Australian offshore islands they have been flushed during the day from rock crevices, occasionally from the crowns of palms, and once from the buttress of a tree. It is possib!e they may also use communal roosting platforms like Forbe's Chestnut Rail in New Guinea (Mayr & Gilliard 1954). Olive (in Robinson & Laverock 1900) noted that 'About dusk they are seen hopping down from thick scrub where they pass the day, to the water, generally in parties of three'. Observations by H. B. G. support the view that these birds could have been coming from roosting platforms. Red-necked Crakes are more often heard than seen. Judging from observations and calls, they are most active at dusk and into the early hours of the evening when they can be seen working their way along creeks in search of food.