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ABSTRACT.-
The foot waggle behavior in Common Loons (Gavia immer) has been postulated to serve primarily as a comfort movement, but may also have a role in thermoregulation. I studied foot waggles in Common Loons during 1994-1996. Foot waggling was most often associated with preening and resting behaviors (81.1%). They were observed also during agonistic encounters with conspecifics, in response to human disturbance (boating), and during social gatherings with other loons. Foot waggle frequency was compared to wind speed, ambient temperature, water temperature, and incident light levels. Wind speed had a negative effect and incident light had a positive effect on adult loon foot waggle frequency. Ambient air temperature and water temperature had no effect on the frequency of foot waggling. Adult loons with young foot waggled 4-5 times more per day during July-August than in May-June, when they were without young. The data suggest the loon foot waggle is primarily a comfort movement, but may also be indirectly involved in attempts by individuals to thermoregulate. Received 29 June 2007. Accepted 25 December 2008.
Common Loons (Gavia immer), diving ducks (Oxyura, Aythya), grebes (Aechmophorus, Podiceps), and mergansers (Mergus, Lophodytes) all foot waggle (McKinney 1965). A foot waggle consists of raising one foot in the air and either holding it there for a brief time, or shaking it, often several times in succession (Mclntyre 1988). The foot may be dipped into the water again and the foot waggle repeated, or it may be placed under the wing, or "shipped" (McKinney 1965). Footshaking (or waggling) removes dirt and suspended particles, that accumulate while swimming, to avoid contamination or wetting of the flank feathers when the foot is shipped (McKinney 1965). Foot waggling occurs most frequently in birds that are about to sleep or rest and is primarily viewed as being a comfort movement (McKinney 1965). However, Lorenz (1953) showed that some comfort movements could serve as signals (e.g., head-shake, tail-shake) but others, that are associated with a disturbance or after copulation, are unlikely to have any signal function (e.g., head-up). Mclntyre and Barr (1997) reported that no quantitative data exist on the Common Loon foot waggle.
Mclntyre (1988) posited the loon foot, due to its large size and extensive vascularization, has a role in thermoregulation. Several...