Moult score
The stage to which moult has advanced at the time when a bird is examined, expressed as a figure representing the sum of the degrees of growth of the new primary feathers, each scored from 0 to 5. As there are usually ten primaries, and only one wing is used in the calculation (the two wings undergoing moult simultaneously) the maximum moult score is 50.From Peter Weaver's Birdwatcher's Dictionary
Copyright © 1981 by Peter Weaver