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Myrtle warbler foot. Macrophotograph of the foot of a myrtle warbler (Setophaga coronata coronata). This bird is a species is a passerine, that is, it belongs to the order Passeriformes. A feature of passerines compared to other orders is the arrangement of their toes, with three pointing forwards and one backwards, which facilitates perching. Photographed by the USGS Bee Inventory and Monitoring Lab: an organisation dedicated to identifying, cataloguing and monitoring bees and other wildlife species. (KEYSTONE/SCIENCE PHOTO LIBRARY/US GEOLOGICAL SURVEY/SCIENCE PHOTO LIBRARY)