207 AUSTRALIAN FIELD ORNITHOLOGY 2008, 25, 207–209 Observations of Commensal Foraging Associations Between the Common Blackbird and Native Australian Species JOHN M. PETER Birds Australia, Suite 2–05, 60 Leicester Street, Carlton, Victoria 3053 (Email: [email protected]) Summary. This note describes two cases of a native bird species feeding commensally with the introduced Common Blackbird Turdus merula while the latter was feeding on the ground: juvenile Masked Lapwings Vanellus miles, and a Brown Thornbill Acanthiza pusilla. In both cases the native species followed, and appeared to benefit from, the Blackbird’s foraging activities. Since the first Common Blackbirds Turdus merula were introduced into south-eastern Australia in the mid-19th century, the species’ range has expanded greatly. Its distribution now extends north into south-eastern Queensland and north-eastern New South Wales, west onto the Eyre Peninsula in South Australia, and south to the edge of the Southwest National Park in southernmost Tasmania (Barrett et al. 2003; Higgins et al. 2006). Within this range, Blackbirds inhabit a variety of habitats, ranging from coastal heathland and scrub to warm-temperate and subtropical rainforest, and occur from offshore islands up to subalpine elevations (Higgins et al. 2006 and references mentioned therein). Throughout this array of habitats, Blackbirds are potentially exposed to many different species of birds, and yet, in their comprehensive review of the ecology and behaviour of the Blackbird in Australia, Higgins et al. (2006) did not uncover any published records of genuine foraging interactions between the Blackbird and any other species of bird, native or introduced, though there were some unpublished anecdotal reports. One of these was the assertion that Blackbirds and Song Thrushes T. philomelos may occasionally feed together (Higgins et al. 2006). This statement, however, probably reflects the birds foraging in close proximity while exploiting a common potential food-source in a common habitat, more in the manner of gulls Larus, ibis Threskiornis and ravens Corvus foraging together in a rubbish tip, rather than a genuine foraging association. There were two other observations mentioned regarding commensal foraging associations of Blackbirds, with Masked Lapwings Vanellus miles and with a Brown Thornbill Acanthiza pusilla. This note is intended to expand on those observations with extra detail. Foraging association with Masked Lapwing At Lunawanna, on Bruny Island in southern Tasmania, on 15 November 2003, I observed a Blackbird foraging on an area of lawn with short grass. It was vigorously and repeatedly probing the soil with its beak. This action left a patch of the short grass, ~40 cm in diameter, looking ‘scuffed up’. Having intensely probed the area for a minute or two, the Blackbird ran from this patch to another area of lawn a few metres away, where it resumed foraging in the same manner for about a minute. It then repeated this behaviour at a third site before flying away, leaving three small areas of lawn ‘scuffed up’ by its foraging activities. While the Blackbird was foraging on the lawn, a group of five Masked Lapwings, probably a family group comprising two adults and three juvenile birds, stood AUSTRALIAN 208 PETER FIELD ORNITHOLOGY nearby. As soon as the Blackbird had left the first foraging site, two of the juvenile Lapwings walked over to the ‘scuffed up’ grass and immediately began probing the grass and soil. It was not noted whether they were successful in obtaining any food. As soon as the Blackbird left the second spot, the juvenile Lapwings immediately ran straight to that patch of grass, and were joined by the third juvenile Lapwing, and all began probing the soil. All three foraged in that area until the Blackbird flew away from the third foraging spot, when one of the juvenile Lapwings ran to forage there, while the other two birds briefly continued foraging at the second spot and then walked away. The effect of the Lapwings following the foraging Blackbird was clear. It is, however, unclear whether it was the vigorous actions of the foraging Blackbird which acted as a visual cue to alert the Lapwings to the potential availability of food, or whether it was the physical changes to the patch of grass (such as loosening the soil) brought about by the Blackbird’s foraging that made the soil easier for the Lapwings to probe. Perhaps there was another effect on the grass, similar to the effect of mowing of a lawn (Devereux et al. 2006), which made the invertebrates in the soil more readily available to be taken by the Lapwings. It has been noted that juvenile Lapwings are reliant on earthworms that have been brought to the surface of the soil (Dann 1981). It is interesting to note that only the juvenile Lapwings were involved in Blackbird-assisted foraging, and that the adult birds remained impassive nearby. It would, therefore, appear that this foraging behaviour was not taught to the young birds by the adults, but was learnt by other means. Foraging association with Brown Thornbill On 20 July 2002 at Gardiner’s Creek Reserve, Bennettswood, in eastern suburban Melbourne, Victoria, I observed a Blackbird foraging on the ground in a clump of dense vegetation within the parkland. The clump comprised a remnant thicket of Swamp Paperbark Melaleuca ericifolia which had been supplemented with plantings of other indigenous shrubs. The ground below the shrubs was mulched with woodchips which were covered with a dense layer of leaf-litter. The Blackbird searched for food among the accumulation of leaf-litter by using its bill to toss loose decomposing debris aside, thereby exposing a moist layer of organic material from which it gleaned invertebrates. As the Blackbird foraged, it was closely followed by a single Brown Thornbill, which also foraged on the ground ~30 cm behind, pecking at tiny invertebrates both among the cast-off sections of leaf-litter and in the shallow depressions excavated by the Blackbird. This mode of foraging appeared similar to the feeding association often recorded between the Pilotbird Pycnoptilus floccosus and Superb Lyrebird Menura novaehollandiae (Wigan 1929; Dickison 1960; Cooper 1972; Smith 1995), and also between the Fernwren Oreoscopus gutturalis and Orange-footed Scrubfowl Megapodius reinwardt (Lindsey 1979), where the larger bird scratches large volumes of leaf- litter aside while foraging, and the smaller bird follows to glean invertebrates thus exposed and flushed, missed or rejected by the Lyrebird or Scrubfowl. This foraging behaviour was observed only once, despite conducting weekly surveys along this section of Gardiner’s Creek for nearly 18 years, and it thus appears not to be a regularly occurring foraging association. These observations indicate that, despite various negative aspects associated with the introduction of exotic species into Australia, as least sometimes, in special (probably opportunistic) circumstances, their presence can benefit native species. VOL. 25 (4) DECEMBER 2008 Native Birds Foraging with Common Blackbird 209 In the cases reported here, it was a native species that followed the foraging Blackbird, rather than vice versa. There are no previous reports of either Masked Lapwings or Brown Thornbills following other foraging bird species in the manner described here, although Brown Thornbills often join mixed-species feeding flocks of other small native insectivorous passerines (Marchant & Higgins 1993; Higgins & Peter 2002). References Barrett, G., Silcocks, A., Barry, S., Cunningham, R. & Poulter, R. (2003), The New Atlas of Australian Birds, Birds Australia, Melbourne. Cooper, R.P. (1972), ‘The occurrence of the Pilot-bird on Wilson’s Promontory’, Australian Bird Watcher 4, 137–143. Dann, P. (1981), ‘Breeding of the Banded and Masked Lapwings in southern Victoria’, Emu 81, 121–127. Devereux, C.L., Whittingham, M.J., Krebs, J.R., Fernandez-Juricic, E. & Vickery, J.A. (2006), ‘What attracts birds to newly mown pasture? Decoupling the action of mowing from the provision of short swards’, Ibis 148, 302–306. Dickison, D.J. (1960), ‘The naming of the Pilot-Bird’, Australian Bird Watcher 1, 76–78. Higgins, P.J.& Peter, J.M. (Eds) (2002), Handbook of Australian, New Zealand and Antarctic Birds, vol. 6, Oxford University Press, Melbourne. Higgins, P.J., Peter, J.M. & Cowling, S.J. (Eds) (2006), Handbook of Australian, New Zealand and Antarctic Birds, vol. 7, Oxford University Press, Melbourne. Lindsey, A.I.G. (1979), ‘A feeding association between Australian Fernwren and Orange- footed Scrubfowl’, Sunbird 10, 47. Marchant, S. & Higgins, P.J. (Eds) (1993), Handbook of Australian, New Zealand and Antarctic Birds, vol. 2, Oxford University Press, Melbourne. Smith, L.H. (1995), ‘The Superb Lyrebird Menura novaehollandiae—a comment on single- species management’, Australian Bird Watcher 16, 169–171. Wigan, L. (1929), ‘Lyrebird and Pilot-bird’, Emu 28, 231. Received 31 August 2007 .