49 AUSTRALIAN Field Ornithology 2011, 28, 49–50 Cartwheeling by Whistling Kites Haliastur sphenurus

LUCAS A. BLUFF School of Biology, Monash University, Clayton, Victoria 3800, and Department of Sustainability and Environment, 574 Main Street, Bairnsdale, Victoria 3875 (Email: [email protected])

Summary. Cartwheeling is a spectacular behaviour in which raptors lock talons in flight and enter a spinning fall. This paper provides the second and third detailed observations of cartwheeling by Whistling Kites Haliastur sphenurus.

Cartwheeling flights involve two individual raptors grasping each other by the talons and spiralling downwards. This behaviour has been observed in at least 39 raptor , typically between conspecifics of larger species (e.g. Haliaeetus spp., Simmons & Mendelsohn 1993). At ~1600 h on 26 August 2010, I observed a group of at least eight Whistling Kites Haliastur sphenurus flying within close proximity of one another, near Dowd’s Morass (Sale, Victoria, 38°10′S, 147°09′E). The were over farmland, ~750 m from my position. As I began observation, two of the group locked talons and cartwheeled toward the ground from an altitude of ~70 m. They rotated horizontally, disengaging just before impact (~5 m above the ground). One landed on the ground in an apparently dazed state and remained there for 20–30 seconds, while the other rejoined the group. I did not continue the observation and, indeed, I was unaware of the rarity of this observation until a coincidence occurred 3 days later. While reading back-issues of The Australian Bird Watcher, I chanced on a short article (Chatto 1985), describing a near-identical observation of cartwheeling in the same species. This is notable for two reasons: (i) it remains the only published and referenced description of this behaviour in the Whistling to date (Marchant & Higgins 1993; Ferguson-Lees & Christie 2001); and (ii) Chatto’s original observation was located at ‘Latrobe River, Sale’, that is, probably only 2–15 km from my own. It is intriguing that both observations occurred within the same small fraction of the species’ substantial range, albeit separated by 25 years. Several hypotheses suggest themselves. For example, it is possible that cartwheeling occurs often and is widespread, but is no longer newsworthy following Chatto’s primary documentation. Alternatively, the behaviour may indeed be rare, but may occur at higher frequency under certain conditions. To investigate the latter hypothesis, I returned to the Dowd’s Morass area on 4 September 2010, with the intention of conducting timed observation of groups of Whistling Kites. The first group was encountered at 1045 h in farmland, 1300 m east of the initial site and 150 m from my position, and comprised two Kites in flight and two perched nearby. One of the perched birds joined the others in flight, and they flew a short distance at low altitude (~20 m) as a group. A pair of these individuals (A and B) fended each other off by rolling and presenting talons. Seconds later, another pairing (B and C) repeated the behaviour. In both cases, physical contact was light or absent. Two of the group then gripped talons and spiralled horizontally while falling ~10 m and completing at least two full rotations before disengaging. The group then disbanded and flew west as single individuals. The time between first sighting of the Kites and the occurrence of cartwheeling was between 60 and 120 seconds. AUSTRALIAN 50 BLUFF: Cartwheeling by Whistling Kites Field Ornithology

Following this event, I spent at least 4 hours in the vicinity of Dowd’s Morass and the Latrobe River, but found only single Kites in foraging flight. That cartwheeling by Whistling Kites was observed twice, 10 days apart, after minimal observation time, suggests that the behaviour is more frequent than would appear from the literature. The factors common to Chatto’s observation and my own are location and social context (i.e. substantial group size: here, eight and four, versus seven in Chatto 1985). Whereas the current events took place in the breeding season (see below), Chatto’s occurred in early February. The only other reported observation of cartwheeling Whistling Kites is a personal communication (D.J. Baker-Gabb in Marchant & Higgins 1993; see also Simmons & Mendelsohn 1993), in which two birds commenced by chasing, then cartwheeled before flying off in the same direction (date and location unknown). Regarding social context, it is worth noting that cartwheeling is commonly misinterpreted as courtship behaviour between mated pairs, but in most taxa is actually agonistic (Simmons & Mendelsohn 1993). The participants of the two cartwheeling events detailed here were almost certainly not mated pairs. The second observation could plausibly have taken place in a territorial defence context between two pairs, as at least one active nest was present at a distance of 1800 m. The first observation, with a larger group size, seemingly does not conform to a territorial interaction, but I was not able to age or sex any of the participants. Finally, it remains unclear whether there is anything unusual about the prevalence of cartwheeling by Whistling Kites in the Latrobe River/Dowd’s Morass area. This location supports the species in large numbers (Chatto 1985; F. Bedford pers. comm.), which would seem predisposing to cartwheeling events. However, equal or greater densities must occur in other parts of the species’ range without recorded cartwheeling—for instance, I have failed to observe cartwheeling in large groups of 10–15 Whistling Kites in the vicinity of Bourail (New Caledonia). More reports of this impressive behaviour are required before its social context and geographic distribution can be determined.

I thank Stephen Debus and Tom Aumann for comments on the manuscript.

References Chatto, R. (1985), ‘Talon grappling by Whistling Kites Haliastur sphenurus’, Australian Bird Watcher 11, 135. Ferguson-Lees, J. & Christie, D.A. (2001), Raptors of the World, Helm, London. Marchant, S. & Higgins, P.J. (Eds) (1993), Handbook of Australian, New Zealand and Antarctic Birds, vol. 2, Oxford University Press, Melbourne. Simmons, R.E. & Mendelsohn, J.M. (1993), ‘A critical review of cartwheeling flights of raptors’, Ostrich 64, 13–24.

Received 14 September 2010 