LONG-TERM TRENDS IN THE ARRIVAL DATES OF SPRING MIGRANTS

Data on the spring arrival dates of 23 species of migrants in Leiceste rshire over a 50-year period are presented. Chiffchaff, Sand Martin, B lackcap and Sedge Warbler showed a significant trend towards earlier a rrival over the period, while Tree Pipit, Cuckoo, Whinchat, Whitethroa t and Garden Warbler showed It significant trend towards later arrival . Fifteen species arrived noticeably earlier in the 1940s, a period of warm springs, while several species showed earlier arrivals in the 19 80s. A number of species showed later arrival dates in the 1960s and 1 970s, when April temperatures were colder than average. Several specie s showed significant correlations between arrival date and temperature . Arrival dates of the earliest species were much more variable than t hose arriving later, while species arriving in the second half of Apri l showed a generally synchronous arrival. The results are discussed in the context of global warming.