Britain holds almost the entire population of the distinctive race flavissima, and so population changes in the UK are of special signficance. Yellow Wagtails appear to have been in decline since the early 1980s, but the reduction in the CBC index is not significant and that in the WBS index may not be representative of the population as a whole. Gibbons et al. (1993) identified a concurrent range contraction towards a core area in central England. BBS results suggest that the decline may be continuing; farmland drainage and the conversion of pasture to arable land have been cited as potential causes (Gibbons et al. 1993). Although sample sizes are small, there has been a significant reduction in brood size over the past 30 years.