Is climate change responsible for local changes in passerine abundance in North America?

Abstract

Human impacts such as habitat loss, species invasions and climate change are thought to be leading to biodiversity losses. However. little is known about the relative magnitudes of these effects. The purpose of this study is to determine to what extent climate change may have been responsible for observed changes in avian species' abundances. I investigated this question using data from the North American Breeding Bird Survey, one of the largest and most comprehensive biodiversity databases available. I found that 40% of the bird populations studied show significant linear changes in abundance from 1970 to 1999. Over the same period, temperature shows significant linear chances at 13% of the survey routes studied, whereas precipitation does not show significant trends. I analyzed the spatial relationships between abundance and climate and found that they are not strong (median R 2 = 0.119) but are generally consistent through time. Temporal trends in abundance were only very weakly related to trends in either temperature or temperature sub-optimality from 1970 to 1999. I found that temperature change is spatially autocorrelated over very long distances, whereas abundance change is autocorrelated over much shorter distances. Observed abundance changes in bird abundance are more likely to reflect local processes such as habitat modification.