The size and shape of a bird’s beak usually give a person an idea of what it eats and how it catches what it eats. Birds such as cardinals have strong, conical bills that crack open nuts and seeds.

How do you know that finches' beak depth is heritable? You can see from Figure 2 that there is a correlation between the parents' and offsprings' beak size. How did the finch population change ...

Few people have the tenacity of ecologists Peter and Rosemary Grant, willing to spend part of each year since 1973 in a tent on a tiny, barren volcanic island in the Galapagos. Even fewer would ...