Altered timing of avian movements in a peri-urban environment and its relationship to climate

Abstract

The peri-urban environment of Langwarrin, near Melbourne, Australia, was used to investigate relationships between local climate and timing of movements in land and waterbirds. From 1976 to 1997, three of 12 species (25%) significantly altered the timing of their arrival, four of 11 species (36%) altered the timing of their departure, and two of 13 (15%) altered the time of their peak abundance. For many species (68%) timing of seasonal movements was significantly correlated with climate, in particular the timing of arrival, peak abundance and for movement in autumn. Minimum temperature appeared to have a greater influence on timing of avian movements than maximum temperature, rainfall or the number of rain-days, and where rainfall or the number of rain-days appeared important it was generally in the season before movement. Although based on a period and location where little warming or drying was observed, the complexity of responses seen by these species indicates that it may not be straightforward to predict the timing of movements of individuals or populations in response to climatic shifts. Given climatic projections of more pronounced warming and drying of this region, this study highlights the need to monitor bird populations continually to determine if species respond predominantly to interannual variability in climate or to, as yet unknown, climatic thresholds.