The growing concern over global warming has renewed interest in phenology, which is the study of the timing of recurring natural events. The analysis of pheological data which indicate the way in which animal and plant species have responded to past environmental changes, particularly those of climate and weather, should help the interpretation of how they may respond to such changes in the future (Fitter et al. 1995; Sparks 1999; Sparks & Carey 1995; Sparks et al. 1997, 2000).
