Phenology is the timing of nature’s cyclical events — when buds burst, insects emerge, and animals migrate and breed — and for birds, getting the timing right is a matter of life and death. A songbird must time egg laying so chicks hatch when food is abundant, especially protein-rich caterpillars. This precise timing evolved over generations – birds’ activities perfectly match their environmental realities to provide offspring good survival odds. But a quickly warming climate means spring arrives earlier and nutritious insect populations boom before birds are ready. Without an ability to adapt to these new conditions in their current locations, many birds face life-threatening phenological asynchrony.
Much research in this area is focused on which species are flexible enough to successfully adapt to these changes, and the secret to their success. For example, Great Tits studied for decades in Wytham Woods (3,000 acres of protected woods and farmland near Oxford, UK) shifted their breeding timing to match the local conditions. A new study on Wytham’s birds looked at the underlying biological causes of these phenological shifts by reviewing how changes in temperature and caterpillar abundance impacted each stage in the Great Tits’ reproductive cycle. A different study reviewed broad geographic trends in North America to reveal that birds at higher latitudes are more vulnerable to the phenological impacts of a warming climate. While insects can adapt quickly when their vegetative food arrives earlier, birds have a less rapid or sensitive response, leaving many bird species increasingly at risk of falling a step behind their food.