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Introduction
Climate can be defined as the prevailing weather conditions (precipitation, temperature, humidity, and other meteorological elements) for a given location over a period of time. Climate fluctuates naturally within a normal range throughout the year and generally adheres to seasonal patterns. Climate change is a long-term shift away from normal climate conditions in a given geographic area. Since the beginning of the 20thcentury, the estimated increase in the average global surface temperature is 0.74°C (Bates et al., 2008), with the greatest changes in temperature observed in the Northern Hemisphere (Hansen et al., 2006; Vose et al., 2005). Consequently, northern geographic areas have experienced consistently warmer winters and earlier spring conditions (Houghton, 2005). Precipitation in Canada is estimated to increase by approximately 20% for the overall annual mean, with winter precipitation expected to increase by approximately 30% by the year 2100 (Bates et al., 2008). However, this increase will likely occur in the form of extreme precipitation events rather than a consistent rise (Palmer and Raisanen, 2002). Climate change will likely increase the instability of weather conditions, provoking a series of extreme weather events, such as droughts, heavy rainfall, and sequences of strong hurricanes, cyclones, and heat waves, for areas all over the world (IPCC, 2007).
Three adaptive strategies have been described in birds as a response to climate change: 1) dispersal into new and acceptable habitats; 2) remaining within their endemic range and adjustment by means of phenotypic plasticity; and 3) adaptation to new conditions via selective genetic changes (Bradshaw and Holzapfel, 2008; Davis et al., 2005; Gienapp et al., 2008). However, as outlined in the review by Crick (2004), there are factors that could prevent or inhibit adaption amongst different bird species: 1) an absence of phenotypic and/or genotypic variability preventing a species from responding to climate change; 2) a lack of dispersal ability that prevents birds from moving into new areas when their own microclimate changes; 3) specialisation, such that species with narrow niches will likely face additional pressure to adapt as climate change rapidly alters their environment; 4) population size, such that the predicted increase in climate variability will likely have a greater impact on species with...