This gadfly petrel drawn by J. G. Keulemans, probably from a museum specimen, is not in a natural posture. Most petrels do not stand up high on their webbed toes, but have most of the next section of the leg (the tarsus) on the ground. They shuffle along, often with some assistance from their wings. Gadfly or white-headed petrels belong to the genus Pterodroma, which includes a quarter of all the petrel species. The name Pterodroma means ‘winged runner’. This petrel, Pterodroma lessoni, was formerly known as Oestrelata lessoni. Gadfly petrels are surprisingly good at climbing trees, which give them a raised launching pad.