Phenology of British butterflies and climate change

Data from a national butterfly monitoring scheme were analysed to test for relationships between temperature and three phenological measures, duration of flight period and timing of both first and peak appearance. First appea rances of most British butterflies has advanced in the last two decades and is strongly related to earlier peak appearance and, for multibrooded speci es, longer flight period. Mean dates of first and peak appearance are exami ned in relation to Manley's central England temperatures, using regression techniques. We predict that, in the absence of confounding factors, such as interactions with other organisms and land-use change, climate warming of the order of 1 degrees C could advance first and peak appearance of most bu tterflies by 2-10 days.