Bird population trends as shown by chick ringing data

Abstract
An index was derived from the annual chick ringing totals for 48 species, over the years 1950–1980 inclusive, and compared with indices calculated from the Common Bird Census and Waterways Bird Survey. Significant correlations were obtained for 18 species and it was concluded that the chick index could be used to examine population trends for these species. However, because of an absence of correlation in 30 species, it was concluded that the chick index presented here cannot generally be used as a population indicator. For the 18 species showing significant correlations, population trends over the 31 year period are described.