Climate change and bird migration in south-eastern Australia

Changes in the timing of migration of birds in relation to climate change have received considerable attention in the northern hemisphere but there have been few studies in Australia. We examined a dataset of first arrival and last departure dates for breeding and non-breeding migrants at Blaxland, west of Sydney, from 1980 to 2011, for temporal trends and for relationships with climatic variables. The 16 species whose arrival dates were analysed have been arriving, on average, 4.4 days earlier per decade. Six species are now arriving significantly earlier than in the 1980s and no species is arriving significantly later. Trends in departure dates (13 species analysed) and length of stay at Blaxland (10 species analysed) varied more. Two species are now departing significantly earlier and one species is departing significantly later. Two species have increased their length of stay and two species have reduced their length of stay. Significant relationships with climatic variables were found mainly between arrival dates and temperature, especially minimum temperature. Six species showed a significant trend towards earlier arrival after periods of higher temperatures along the migration route, whereas one species showed a trend towards later arrival after higher temperatures. These results are consistent with the general trend towards earlier arrival of migratory birds that has been reported in the northern hemisphere and linked to rising temperatures from climate change. This study provides evidence that migratory birds in the southern hemisphere are responding to climate change in a similar way to birds in the northern hemisphere.