One can imagine a biological need for plants and animals to respond to changing climate. So as it gets warmer, for example, evolutionary pressure might favor birds that lay their eggs sooner in the spring. But Daniel Nussey and a team at the Netherlands Institute of Ecology and the University of Edinburgh’s Institute of Evolutionary Biology found a much more interesting and subtle thing happening with a Dutch population of Parus major – the great tit.
For Parus major, climate change is a problem. As Elizabeth Pennisi explained in the Science news piece, the birds time their egg-laying so the chicks hatch when there are gobs of caterpillars to eat. With climate warming, that happens sooner in the year.
One can easily imagine a rather simple drift resulting, favoring earlier egg-layers. But the researchers found something more complex going on. The birds were evolving toward a greater “plasticity” in their egg-laying behavior. Rather than a fixed genetic switch that allowed them to lay eggs earlier, evolution was favoring birds that seemed to have more flexibility in their egg-laying in response to changes in climate. As Pennisi put it:
Most of the birds did not adapt and maintained their original schedule, and the numbers of surviving offspring have begun to decline. But there were some exceptions. Even in the 1980s, some individuals altered their behavior in accordance with the climate, laying eggs earlier in the warm years and later in the cool years. These climate-attuned females have twice as many surviving offspring.