Published online by Cambridge University Press: 27 March 2009
An index of feather cover is described and applied to assess the coats of various birds. Feather area indices were calculated, by analogy with the leaf area index used by crop ecologists, as the projected area of feathers above unit area of skin. Measurements were made on samples from chickens, turkeys, pheasants, sparrows and herring gulls. The index was calculated for feather tracts on six areas of the body. An overall area index was also calculated, based on the feather cover of at least 60% of the bird's body surface. Intra- and interspecific differences were large. Between species there was a positive correlation between feather index and body weight, while within species, for poultry at least, the opposite was found. This characterization of the feather coat is discussed in terms of its possible use as an index of the insulation of feathers.