Dusky Woodswallows: Feeding of Juvenile with Bill Malformation by Another Juvenile On the morning of 2 February 1997, I was watching feeding behaviour of a loose flock of about 20 Dusky Woodswallows Anamus cyanopterus in an area of open woodland on 'Callum Brae' sheep-grazing property, just south of the inner southern suburbs of Canberra, A.C. T. About a dozen adult birds were feeding several obvious juveniles 2-5 months old. Independently, two or three foraging juveniles were engaging in active hang-gleaning in the outer foliage of nearby mature eucalypts, mainly Red Box Eucalyptus polyanthemos. AUSTRALIAN 350 DABB BIRD WATCHER The 'long-billed' juvenile Dusky Woodswallow in begging posture Plate 54 Photo: Geoffrey Dabb Hunched 'long-bill' faces expected feeder Plate 55 Photo: Geoffrey Dabb VOL. 17 (7) SEPTEMBER 1998 Juvenile Dusky Woodswallow Feeding Another Juvenile 351 'Long-bill' fed by second juvenile Woodswallow Plate 56 Photo: Geoffrey Dabb A moment later, both juveniles side by side. Note similar plumage. Plate 57 Photo: Geoffrey Dabb AUSTRALIAN 352 DABB BIRD WATCHER The young birds could be distinguished and roughly aged by their mottled underparts, buff spotting and some mottling on head and back, and bill colour of mauve or pinkish hom in place of the distinctive adult blue-grey. By contrast with newly fledged birds seen in spring and early summer, these February juveniles were of adult proportions or nearly so, showing the usual progression from fledgling to sub-adult. Dusky Woodswallows are migratory in the Canberra region, with most adults returning in September and the first young being seen no earlier than October (Taylor & COG 1992) aild, accordingly, juveniles seen in late summer can be assumed to be the result of breeding activity in the previous spring in the Canberra region or farther south. About 7-8 m away, I noticed an unusual young Dusky Woodswallow engaged in apparent begging behaviour of head-lowering, wing-extending and wing-fluttering. This bird had a malformed bill, thin and elongated, rather like a Lichenostomus honeyeater's, and with a small bump on the upper mandible. A few seconds after I focussed my camera on this unusual bird, a Woodswallow which looked like another young bird alighted beside it and immediately fed it a small piece of food. The feeding bird was probably one of the foliage-gleaners as it came from the direction of that activity. The two birds remained perched side by side for a few seconds before flying off. Later, I noticed the juvenile with the distinctive bill being fed by an adult Woodswallow. On examining the developed slides (Plates 54-57) I found that they had captured reasonably well the feeding sequence described. In addition, the final photograph of the two birds together shows sufficient detail to indicate that they are of the same age, possibly siblings from the same nest. Assessment of both as juvenile birds is consistent with the criteria in Rogers et al . (1986). All photographs are of the one perch within a few seconds of one another; the birds shown are the fed (thin-billed) and feeding (normal-billed) juvenile birds. Dusky Woodswallows are recognised co-operative breeders, in that birds other than parents are recorded as feeding young birds (Schodde & Tidemann 1986, Strahan 1996). This observation suggests that non-parental feeding of young birds may be behaviour that develops early in life, and may emerge as feeding by advanced juveniles of same-year siblings, even, perhaps in exceptional circumstances, of brood-mates. References Rogers, K., Rogers, R., Rogers, D. , Lane, B. & Male, B. (1986), Banders Aid: A Guide to Ageing and Sexing Bush Birds, Rogers, St Andrews (Vic.). Schodde, R. & Tidemann, S.C. (Eds) (1986), Readers Digest Complete Book of Australian Birds, 2nd edn, Readers Digest Services, Sydney. Strahan, R. (Ed.) (1996), Finches, Bowerbirds & Other Passerines of Australia, Angus & Robertson, Sydney. Taylor, I.M. & Canberra Ornithologists Group (1992), Birds of the Australian Capital Territory: An Atlas, Canberra Ornithologists Group and National Capital Planning Authority, Canberra. By GEOFFREY DABB, 24 Brockman Street, Narrabundah, A. C. T. 2604 Received 6 February 1998 • .