Influence of climate change on Avian Migrants' first arrival dates

Long-term studies over a variety of regions, species, and time periods can help link trends in climate to changes in bird phenology and provide better understanding of potential effects of climate change. We analyzed first spring arrival dates of 93 species of migrants from the Buffalo Ornithological Society's database covering the period from 1967 to 2008. Migrants appeared a mean 0.10 days earlier each year. Short-range migrants, traveling from a winter range within North America, have advanced their average arrival more, 0.15 days per year, than have long-range migrants from Central America, South America, or the West Indies, whose advance averaged 0.06 days per year. We regressed arrival dates against the temperature of short-range migrants' winter range, as represented by Houston, Texas, and the North American Oscillation Index as indicators of climate change. The Houston temperature correlates well with earlier arrival dates, especially for short-range migrants. We compared our results with similar studies across North America and found general agreement with the trends we observed. These results are consistent with the hypothesis that climate change has a strong influence on the phenology of bird migration.