AUSTRALIAN 6 BIRD WATCHER AUSTRALIAN BIRD WATCHER 1989, 13, 6-19 Miscellaneous Notes on the Bowerbirds Chlamydera cerviniventris and C. lauterbachi (Ptilonorhynchidae) in Papua New Guinea by C.B. FRITH and D.W. FRITH 'Prionodura', Paluma via Townsville, Queensland 4816 Summary Nests, a nestling and three bowers of the Fawn-breasted Bowerbird Chlamydera cerviniventris are described, and observations of parental nest attendance reported. Nests, eggs and bowers of Lauterbach's Bowerbird C. lauterbachi are described and observations of male and female behaviours at a bower reported. First descriptions of nestling, fledgling and juvenile Lauterbach's Bowerbird are given. The location of nests relative to bowers and seasonality of nesting of the Fawn-breasted and Lauterbach's Bowerbirds are reviewed. Introduction The four or five Chlamydera bowerbird species (Ptilonorhynchidae) are unlike the other fourteen, forest-dwelling, species in that they inhabit only open drier habitats of riverine forests, open woodlands, grasslands and adjacent forest edges (Donaghey et al. 1985). They are all members of the 'avenue' bower building group but differ from Sericulus and Ptilonorhynchus species, in which males are brightly coloured, by being dull and cryptically sexually monomorphic or very nearly so (Gilliard 1969). Least known of the Chlamydera species are Lauterbach's Bowerbird C. lauterbachi endemic to central and north-eastern New Guinea, and the Fawn-breasted Bowerbird C. cerviniventris of north-western Cape York Peninsula, Australia, and coastal central and eastern New Guinea and the eastern Vogelkop (Cooper & Forshaw 1W7) . Other than descriptions of bowers, some male displays and nest and eggs, little is known of nesting habits and nest dispersion relative to bower locations in Lauterbach's and Fawn-breasted Bowerbirds (Peckover 1969, Cooper & Forshaw 1W7). It is commonly assumed that males are promiscuous, and females alone attend the nest (Gilliard 1969, Peckover 1969, Cooper & Forshaw 1W7, Diamond 1982, 1986) but no direct evidence of this is available. During 3 to 5 December 1985 we examined bowers and nests of the Fawn-breasted Bowerbird in a previously unknown location, in the Lai River valley (Frith 1987) . During a brief trip to Baiyer River Sanctuary, Western Highlands Province, Papua New Guinea in November 1W7 we examined three active bowers and one active nest of Lauterbach's Bowerbird. We returned in November 1985 and spent 52 hours observing an active bower and 12.5 hours photographing a presumed female at her nest and egg; and examined several nestling, fledgling and juvenile specimens in the Baiyer River Sanctuary and Papua New Guinea National Museum collections. Our observations include new facts which add to the limited knowledge of these birds. Results Fawn-breasted Bowerbird Observations of this bowerbird were made at Ruti Cattle Station on the Lai River, Jirni Valley, Western Highlands Province, Papua New Guinea, during 3 to 5 December 1985. Three active bowers and one active and two disused nests were examined within 1.5 kilometres of Ruti Homestead. VOL. 13 (1) MARCH 1989 Notes on Bowerbirds in Papua New Guinea 7 Nest 1 was 1300 mm above ground in a 2.25 m tall, well-foliaged sapling located in grassland approximately 250 m from the rainforest edge (see Plate 6a) and 400 m from the nearest known bower (#1). At midday on 3 December 1985 this nest contained a tail-less nestling with flight feathers in pin, a wing length of 48 mm, and the bird's first (inner) primary 30 mm entirely in pin. Its eyes were open. Tawny-grey down was conspicuous on crown and body, the bill was black with an obvious white egg tooth, and the gape a dull dark white. Breast and flank feathers were in pin but were clearly seen to be dark fawn in colour through the sheaths. Mouth colour was bright orange-yellow, and skin dark flesh. Nestling weight was greater than 50 grams, the maximum of the scales available at the time. At 1200 hours on 4 December nestling wing length was 56 mm, the first (inner) primary 35 mm entirely in pin, and skull plus bill length, or total head length (THL) 40.3 mm. At midday on 5 December wing length was 61 mm and first primary 40 mm long, entirely in pin. Observations of parental care were made at nest 1 on 4 December from 0700 to 1200 and 1400 to 1700 h from a hide 15 m distant, using 8 x 30 binoculars. We gained the distinct impression that only one parent, assumed to be female, attended the nest. The same few routes to and from the nest were repeatedly used and at no time was there any suggestion of two birds in the area, notwithstanding the open country and good visibility about the nest tree (see Plate 6a). The parent was present (in nest tree, on nest rim, or brooding) for only 10.6 % of the eight hour watch. The only three brooding bouts (0.4 per hour) averaged 2 minutes 34 seconds in length. Twenty-one feeding visits (2.6 per hour; mean duration 57 seconds) were made to the nest. During twelve feeding visits the nestling meal could not be identified; three meals consisted of a fruit, and six were of insects of which three were caterpillars. All meals were carried in the bill, not regurgitated to the nestling. All nestling faecal sacs were swallowed by the parent; one sac examined contained remains of several beetles. Empty nests 2 and 3 were located in grassland adjacent to the rainforest edge, 20 m and 80 m respectively from active bower #1 which was located just 4 m from the grassland into the rainforest edge. Nest 2 was a recently disused nest of the current season and nest 3 older and perhaps of the previous season. All nests were in small, isolated, well-foliaged trees within the grassland, the nests being built into near-vertical forks of branches. Table 1 presents measurements of all three nests. Sticks of the foundations of these nests measured up to 450 mm in length and 5 mm in diameter, and extended up to 300 mm outward and beyond the outer nest rim. A substantial symmetrical cup nest of tendrils is built into the stick foundation and a discrete nest­ cup lining of fine twiglets and vine tendrils within that (see plate 6b). The first two bowers examined were consistent with Peckover's (1969) observations in having their central avenue orientated within 30° of east-west, being at 255 o and 290° for bowers 1 and 2 respectively; bower 3 being approximately at 225° (R.D. Mackay pers. comm.). Bower 2 was unusual in having only one stick platform, at its eastern (110°) end of the avenue and this decorated with 35 round green fruits 10 to 21 mm in diameter. Peckover, however, stated that with very few exceptions bowers are decorated on the west platform, and did not note that any of his 85 examined bowers lacked one platform. In addition, bower 2 also lacked sticks on the ground to the north of the avenue wall and this area had, moreover, been meticuously cleared of all debris down to the black soil. Other than this anomaly the two Jimi Valley bowers were typically laid out and decorated, and were of dimensions within recorded extremes for the species. Sticks of the outer avenue walls measured up to 3.5 mm in diameter. AUSTRALIAN 8 FRITH & FRITH BIRD WATCHER Sticks of the inner avenue walls were very much finer but there was no hair-like rootlet fibres lining the extreme inner wall as observed in bowers belonging to Lauterbach's Bowerbirds. Lauterbach's Bowerbird Observations were made in and about Baiyer River Sanctuary, where local people call the species 'Takagul'. Nest 1 was 2 m high in a well-foliaged small tree in grassland of an old native garden 50 m from an active bower. This unmeasured nest contained one egg, measuring 38.5 x T7.3 mm and weighing 14.5 g on 5 November 1fJ77. Chaffer (1949) provided a fine plate of a similar nest and egg. Nest 2 was found on 22 November 1985, within 200 m of the above, still-active, bower in a sparse clump of Helianthus shrubs intermixed with and surrounded by tall blady grass within native gardens. This nest was built between near-vertical fork stems of a Helianthus. It consisted of a sparse and rather haphazard foundation of sticks, up to 500 mm long and 5 mm diameter (predominantly c. 300 mm long and (3 mm diameter) supporting a neat compact cup of fine twigs and vine tendrils 1.5 to 0.6 mm diameter and up to c. 200 mm long (Plate 7c). The tendril-lined cup was strong, but could be seen through in places. Some foundation sticks extended up beside the nest rim and above it as much as 140 mm. Some of these sticks extended out away from the outer cup rim up to 280 mm. Foundation sticks were dry and pale grey, whereas the cup was of moister dark brown tendrils. Measurements appear in Table 1. This nest contained one egg measuring 39.9 x Tl.O mm and weighing 14.7 g. During the 12.5 hours that CBF spent photographing incubation activity at this nest (see Cover Plate) from a hide, the distinct impression was gained that only one bird, assumed to be female, was involved. Nest 3 was found on I December 1985 in a small clump of Acalypha mixed with Helianthus shrubs, amidst native gardens, within less than 200 m of a disused bower which locals knew to be in use some weeks earlier.