A period of very low rainfall occurred while the Grants were on the islands. The drought resulted in fewer seeds for the finches to eat. Birds with smaller beaks could eat only the smaller seeds. Birds with bigger beaks were better off. They could eat seeds of all sizes. Therefore, there was more food available to them. Many of the small-beaked birds died in the drought. More of the big-beaked birds survived and reproduced. Within just a couple of years, the average beak size in the finches increased. This was clearly evolution by natural selection.
Mike was sitting in the yard of his new home when he noticed that there were a lot of squirrels in the area. Some of the squirrels were very good at gliding from tree to tree by spreading their legs apart the others often had to run across the ground and then climb another tree. Mark also observed several cats in the area watching carefully as the squirrels scampered across the ground to other trees.
In a few years will there be more or less nongliding squirrels?