Some aspects of adaptation and evolution in Australian Fan-tailed Flycatchers

Abstract

In the genus Rhipidura, the typical fan-tailed flycatchers such as the Grey Fantail R. fuliginosa are arboreal and the erected and fanned tail appears to be used for scaring insects into flight so that they can be captured. The Willie Wagtail R. leucophrys shows terrestrial adaptations. Vertical tail-fanning is replaced by wing-flashing and some characters of plumage-pattern, voice and nesting may be related to the more open habitat used by the species. Osteologically its legbones are longer and its pelvis slightly longer and narrower, which may be correlated with its terrestrial habits. The Northern Fantail R. rufiventris is a more sluggish arboreal species, capturing insects in short flights from a perch and lacking the tail-erecting behaviour. Its leg-bones are short relative to those of the Grey Fantail, but similar in proportion to those of some monarchine flycatchers, and this may be correlated with more sedentary behaviour. These behavioural differences linked with morphological divergence may justify the re-use, as subgeneric or generic divisions, of the names Leucocirca for the Willie Wagtail and Setosura for the Northern Fantail and related species. The Willie Wagtail probably evolved in Australia in a refuge area with a more oven habitat but the Northern Fantail probably evolved in forests of the New Guinean region.