The Eastern Whipbird: a Seed Predator of the Endangered Caley's Grevillea Grevillea Caleyi

VOL. 25 (2) JUNE 2008 99 AUSTRALIAN FIELD ORNITHOLOGY 2008, 25, 99–101 The Eastern Whipbird: A Seed Predator of the Endangered Caley’s Grevillea Grevillea caleyi CARL R. GOSPER and TANYA M. LLORENS Institute for Conservation Biology, University of Wollongong, Wollongong, New South Wales 2522 (Present address: Department of Environment and Conservation, Locked Bag 104, Bentley Delivery Centre, Western Australia 6983; email: [email protected]) Summary. This note describes an observation of an Eastern Whipbird Psophodes olivaceus collecting, manipulating and feeding on the seeds of the endangered shrub Caley’s Grevillea Grevillea caleyi. An Eastern Whipbird Psophodes olivaceus was observed destructively consuming seeds of Caley’s Grevillea Grevillea caleyi (Proteaceae) on 21 September 2000. This occurred in dry sclerophyll forest of Silvertop Ash Eucalyptus sieberi and Red Bloodwood Corymbia gummifera, above a dense shrubby understorey dominated by Caley’s Grevillea, Myrtle Wattle Acacia myrtifolia and Silver Banksia Banksia marginata, in Ku-ring-gai Chase National Park, Sydney, New South Wales. The bird came to the attention of the observer (CG) by behaving in an unusual manner for the species, within a plot being monitored for floral visitors to the Grevillea. The bird was jumping from perches to the outer foliage of the Grevillea shrubs, and after appearing to snatch an item in its bill, it fell downwards through the foliage to a lower perch or to the ground. After a short period, the bird then moved up through the shrubbery and repeated the process. This behaviour continued for several minutes before the bird moved to a position ~10 m from the observer, where it was visible through a less dense section of the vegetation that enabled a closer examination of the bird’s behaviour. When the Whipbird repeated the jump, snatch and fall manoeuvre, the item snatched was observed to be a large fruit, which was held in the bill while the bird was on the ground. The bird then dropped the fruit to the ground, hit it vigorously several times with its bill, consumed fragments of it and then continued into dense vegetation and out of sight. The location where the bird fed was inspected and fruit fragments were collected and photographed. Only fragments of the pericarp (follicle wall) of the fruit could be found, and were identified as being from Caley’s Grevillea. No remains of the seed were located, so it is presumed that the seed formed the bulk of the material consumed. The colour of the pericarp indicated that the fruit was not yet mature enough to have shed the seed. The observation described here is of interest because few plant foods have been recorded for the Eastern Whipbird, and fewer instances of seed predation. Robertson & Robertson (1999) recorded Whipbirds eating the seeds of Arum Lilies Zantedeschia aethiopica and Sunflowers Helianthus annuus in a manner similar to this observation, with birds removing the inner part of the seeds. Other seeds have been identified in Whipbird stomach or faecal contents (Barker & Vestjens 1990; French 1990; Rose 1999), where fleshy fruits may have been the food digested, and Frith (1992) described the systematic inspection by Whipbirds of Yellowheart Fagraea gracilipes [now F. fagraeacea] fruit and consumption of what was presumed to be insect larvae from within the fruit. Although mature AUSTRALIAN 100GOSPER & LLORENS FIELD ORNITHOLOGY Caley’s Grevillea fruit often contain weevil larvae (Auld & Denham 2001a), in this case the Eastern Whipbird consumed the bulk of the seed and made no effort to separate from the seed any larvae that may have been present, suggesting that the seed itself may have been the desired food. Nonetheless, the possibility that the bird was ingesting insect larvae cannot be discounted. Robertson & Robertson (1999) suggested that it is surprising that there are so few reports of Whipbirds eating plant material. As our observation describes the activities of a single bird, it is not possible to speculate as to whether this behaviour and food are common for Whipbirds within the range of Caley’s Grevillea. The behaviour was not observed on any other occasion during 18 hours of observation of pollinators at this and other sites, although Whipbirds were not the primary subject of these observations and were rarely observed. However, for this bird and at this time, a substantial number of Grevillea seeds were being consumed and the bird was deliberately and repeatedly seeking them. Caley’s Grevillea typically has a single relatively large, ellipsoidal seed (15–20 mm long and 4–5 mm wide, within a fruit 17–21 mm long and 8–11 mm wide) (Olde & Marriott 1995). Fruits mature on the plants, with the follicle splitting on maturity and shedding the seed. The breaking up of the fruit on the ground by the Whipbird may have served to remove the less edible fruit pericarp and expose the seed, and/or break the seed into more manageable fragments, for swallowing. This observation is also of interest in the conservation of Caley’s Grevillea, an endangered (Environment Protection and Biodiversity Conservation Act, NSW Threatened Species Conservation Act) shrub with a severely restricted range. The Eastern Whipbird had not previously been identified as a contributor to seed predation in Caley’s Grevillea. The damage inflicted on the fruit’s pericarp strongly indicates that the seed would have been considerably damaged by the Whipbird, most likely rendering the seed incapable of germination. Caley’s Grevillea also suffers pre-dispersal fruit predation by weevils (Auld & Denham 2001a) and parrots (Auld et al. 1993), and extensive post-dispersal seed predation by mammals (Auld & Denham 2001b). High levels of seed predation in this grevillea retard the development of the seed bank, and threaten smaller populations with extinction (Regan et al. 2003). Acknowledgements The New South Wales Department of Environment and Climate Change and the University of Wollongong’s Institute for Conservation Biology provided funding support to TL for research on Caley’s Grevillea. We thank Tony Auld and David Ayre for comments on drafts of the manuscript. References Auld, T.D., Bradstock, R. & Keith, D. (1993), Fire as a Threat to Populations of Rare Plants, Australian National Parks & Wildlife Service Endangered Species Program 31. Auld, T.D. & Denham, A.J. (2001a), ‘Predispersal seed predation in shrubs of Grevillea (Proteaceae) from south-eastern Australia’, Australian Journal of Botany 49, 17–21. Auld, T.D. & Denham, A.J. (2001b), ‘The impact of seed predation by mammals on post- fire seed accumulation in the endangered shrub Grevillea caleyi (Proteaceae)’, Biological Conservation 97, 377–385. Barker, R.D. & Vestjens, W.J.M. (1990), The Food of Australian Birds 2, Passerines, CSIRO, Melbourne. French, K. (1990), ‘Evidence for frugivory by birds in montane and lowland forests in south- east Australia’, Emu 90, 185–189. VOL. 25 (2) JUNE 2008Eastern Whipbird Eating Grevillea Seeds 101 Frith, C.B. (1992), ‘Eastern Whipbird Psophodes olivaceus (Orthonychidae) listens to fruits for insect prey’, Sunbird 22, 32–33. Olde, P. & Marriott, N. (1995), The Grevillea Book, vol. 2, Kangaroo Press, Kenthurst, NSW. Regan, H.M., Auld, T.D., Keith, D.A. & Burgman, M.A. (2003), ‘The effects of fire and predators on the long-term persistence of an endangered shrub, Grevillea caleyi’, Biological Conservation 109, 73–83. Robertson, S. & Robertson, A. (1999), ‘Feeding habits of the Eastern Whipbird’, Bird Observer 803, 15. Rose, A.B. (1999), ‘Notes on the diet of some passerines in New South Wales 1: Fairy-wrens to woodswallows’, Australian Bird Watcher 18, 106–120. Received 6 November 2006 .

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