AUSTRALIAN 160 KLOOT: Grey Foraging Method WATCHER

Grey Currawong Strepera versicolor Employs the 'Zirkeln' Method in Searching for Food

'Zirkeln' feeding, from the German 'Zirkel', meaning circle, sometimes called 'prying' or 'open-bill probing' entails forcing the closed bill into fruit (, Zosteropidae) or the earth (Starlings, Sturnidae) (Kloot & McCulloch 1980). Goodwin (1967) also stated that the Yellow-throated Miner Manorinajlavigula ' . .. habitually "zirkelns" ... probing into crevices and under debris and then opening wide its bill to enlarge the space and expose hidden prey'. Apparently starlings, at least, use this method from a very early age. I have held a young Sturnus vulgaris on my palm. It immediately pecked at my hand, searching for food, and as it placed its between my closed fingers I distinctly felt it striving to force them open in an attempt to 'zirkeln'. According to Lorenz (1949), part of the head morphology of some of these is correlated with 'circling'. Between the eye and beak the skull is deepened in the form of a groove. Thus the bird is able to look easily down the beak to sight its food. Feare ( 1985) states ' ... notably in the genera Creatophora, Acridotheres and Sturnus . .. the muscles that open the bill, the protractors, have become well developed in comparison with those in frugivorous and insectivorous, mainly aboreal, species'. Kunkel (1962) also observed that besides 'circling' in their search for food, both the Cape White-eye Zosterops pallidus and the Oriental White-eye Z. palpebrosa do this in mutual preening of their partner's feathers, but not their own , as reported by Kramer (1930) for the Icteridae. Perhaps 'circling' is used more than is generally observed. On 13 September 1991 , at 0800 h on a sunny morning, at a property at Woodend, , I observed a Strepera versicolor employ the 'zirkeln' method in a search for food. Unlike the beak of the S. graculina, the hook on the Grey Currawong's is only slight. The bird was seen to hold a piece of curled eucalypt bark firmly with its foot, against the branch on which it sat. As this tree was an acacia it had obviously carried the bark into the tree, but I did not see this happen. Inserting its beak into a split, the bird then proceeded to slide it along the length of the bark. Opening its beak, four or five times at intervals of approximately 3-4 em, it was obviously seeking food items. Twice it opened its beak quite widely as it worked its way along the entire piece of the bark. When satisfied that the bark contained no food, the bird flew off, leaving it on the tree. I retrieved the curl of bark and on examination saw that it contained cobwebs. Apparently it was the cobwebs that drew the bird's attention to these as a potential food source. The bird was approximately six metres from me and I observed the entire procedure through 8.5 x 44 binoculars. This observation is consistent with the Grey Currawong being a more specialised bark-forager than the Pied Currawong (Schodde & Tidemann 1986).

References Feare. C.J. ( 1985), 'Starling: Food', in Campbell , B. & Lack E. (Eds), A Dictionary ofBirds , Poyser, Calton. Goodwin. D. (1967), 'Notes on behaviour of some Australian ' , Emu 66, 237-251. Kloot. T. & McCulloch. E.M. (1980), Birds of Australian Gardens, Rigby, Adelaide. Kramer. G. ( 1930). 'Bewegungsstudien an Vl)geln des Berliner Zoologischen Gartens', J. Ornithol. 78. 257-268. Kunkel. P. (1962). 'Bewegungsformen, Sozialverhalten, Balz und Nestbau des Gangesbrillenvogels (Zosterops palpebrosa Temm.)', Zeits. f Tierpsychol. 19, 559-576. VOL. 15 (4) DECEMBER 1993 LEY: Parrot Food 161

Lorenz, K. (1949), 'Uber die Beziehungen von Kopfform und Zirkelbewegung bei Sturniden und Icteriden' , Ornithol. als. bioi. Wissensch. , Festschr. Stresemann, Heidelberg, 153-157. Schodde, R. & Tidemann, S.C. (Eds) (1986), Reader's Digest Complete Book of Australian Birds, 2nd edn, Reader's Digest Services, . By TESS KLOOT, 81114 Shannon Street, Box Hill North, Victoria 3129 Received 22 April 1992 •