These days, we hear a lot about the effects of climate change on species and habitats. Scientific studies looking for a link between climate change and animal behaviour often focus on birds, and for good reason. Birds are one of the best known groups of species on the planet, they are found in virtually every habitat, and much of their life cycle (like egg laying and migration) is often intimately linked to climatic conditions.
A new study in Global Change Biology
provides more evidence that a warming climate is directly affecting bird behaviour. Researchers found that many birds migrating to or through the eastern U.S. are arriving earlier. This times their arrival to correspond to optimal food and habitat conditions like insect emergence and leaf budding which occur earlier in the spring as the climate warms. (News Report: Science Daily
Interestingly, this study also finds that long-distance migrants don’t migrate earlier. They aren’t able to use local climate cues to time their migration departure in the same way that shorter-distance migrants do. As a result, birds that winter in South America may face conditions along their migration route and on their breeding grounds which are far less than optimal, particularly in warm years. It’s not a pretty picture to imagine the all too plausible scenario of our boreal warblers returning to their breeding grounds only to have missed the massive pulse of insects on which they depend.