Fig. 3.1.

Relationship between brain volume and body mass in the tawny frogmouth and other birds. (a) The tawny frogmouth (arrow) is compared to a representative group of nightjars (hollow circles) and to several other large sized native Australian birds from different orders (black filled dots). The weights of these birds (shown in brackets) are: Australian magpie (280 g), Australian raven (635 g), sulphur crested cockatoo (726 g), brown goshawk (403 g), osprey (1450 g) and wedge-tailed eagle (3814 g). Note that there is a cluster of eight nightjars in the weight range of 41 g to 257 g, all with relatively similar brain/bodyweight ratios (from lightest to heaviest): the Australian owlet-nightjar, whip-poor-will, spotted nightjar, large tailed nightjar, chuck will’s widow, white-throated nightjar, Nacunda nighthawk, and the grey potoo. The oilbird (414 g) is above the nightjar trend line and the tawny frogmouth (387 g, see arrow) is well above all other nightjars. (b) The tawny frogmouth (marked with arrow, hollow circle) is compared with Australian owls (black circles) of two families (Ninox and Tyto). The weights of these birds vary quite substantially (shown in brackets, as averages): the powerful owl (1350 g), rufous owl (820 g) and masked owl (593 g), barking owl (592 g) and sooty owl (585 g), barn owl (360 g) and grass owl (372 g) and the southern boobook owl (234 g). In weight range, the tawny frogmouth (388 g) fits in well, being slightly smaller than the barking and sooty owls and slightly larger than the barn and grass owls, but owls in general have larger brain/bodyweight ratios than the tawny frogmouth.