Water Flux in Malleefowl, Leipoa-Ocellata Gould (Megapodiidae)

Abstract

Water efflux of captive and free-ranging malleefowl Leiopa ocellata (body mass 2.0 kg) was monitored over a complete annual cycle. Water efflux in captive adult birds remained relatively constant throughout the study period and averaged 26.3 ml. kg-'.d-', which is 30% of the predicted rate based on allometric criteria. Water efflux of free-ranging birds was higher and more variable than in captive birds and averaged 49.0 ml. kg-'.d-', 56% of the predicted rate. The low water efflux rates of malleefowl indicate that this species is well adapted to an arid environment. Multiple regression analysis failed to find a significant relationship between rainfall or mean air temperature and water efflux rate in free-ranging birds. An examination of the literature on avian water flux indicated that rates obtained from studies on captive birds are lower than those obtained from free-ranging birds; it is suggested that allometric analysis should take this factor into account. Two allometric equations are presented, one for captive birds, the other for free-ranging birds.