Roosting behaviour of the tawny frogmouth (Padargus strigoides)

We characterized the day roost sites of four pairs and one solitary tawny f rogmouth Podargus strigoides in a woodland in south-eastern Australia. The birds were equipped with radio transmitters which enabled us to locate them daily from autumn 1997 to late summer 1998. Tree species, tree size, roost height and orientation of the roosting bird were recorded. Over the study period tawny frogmouths frequented a large number of day roosts (up to 71 p er pair). Birds rarely used the same roost over extended time periods and m ost roosts were used for less than 3 days. Mature trees with a girth of mor e than 0.5 m were preferred as day roosts. Tawny frogmouths exhibited a sig nificant preference for the coarse and dark-barked stringy-bark trees, but other tree species such as the smooth-barked, light-coloured gums were also frequented. However, when roosting in gum trees, dead branches were prefer red, presumably as these have a coarser appearance than living branches and therefore provided better camouflaging. Especially during winter, the bird s showed a significant selection of branches on the northern side of roost trees presumably to maximize sun exposure. During summer, two pairs maintai ned a significant northerly preference, whereas the others used roosts with random orientations. Small-scale seasonal movements in the area used for d ay roosting were also observed, with two pairs selecting a distinct area wi th a south-westerly aspect during summer which appeared to have less sun ex posure. Our study suggests that tawny frogmouths select roosts to (1) minim ize visibility from day predators and (2) to facilitate passive thermoregul ation by sun-basking.