Galapagos Finches

Galapagos Islands

The Galapagos Islands

The Galapagos Islands are one of the most spectacular landscapes in the world and home to a variety of species that live nowhere else. Finches are abundant in the region, and currently, there are about 13 species of finches. DNA evidence tells us that all of the finches are more related to each other than anyone is to a species on the mainland. In fact, one finch species arrived on the archipelago and diversified into the 13 species that we see nowadays.

Peter and Rosemary Grant

Peter and Rosemary Grant

Peter and Rosemary were two researchers that went to the Galapagos Islands for research on evolution. They decided to study how the shape and size of the beaks of the finches changed over time. They rose at 5:30 each morning to net the island’s ground finches. They measured the size and shape of each bird’s beak, the bird’s weight, and tagged them for identification.

1977 Drought

1977 Drought

Peter and Rosemary Grant first witnessed evolution during a 1977 drought. In 1977, no rain fell for the next 18 months. Vegetation disappeared, but cactus bushes were still there. Medium ground inches had to compete for scarce food. As small seeds became scarce, finches had to compete for medium, large seeds. Only birds with large beaks could crack open the large seeds. Birds with the smallest beaks had the most trouble. As a result, over 80% of medium finches died.

1983 Rain

1983 Rain

Five years after the drought, rain fell ten times more than usual. The island was overrun with vines. Smaller seeds were abundant because the vines that covered the island produced small seeds. Larger grains became scarce, on the other hand, became scarce. Birds with larger beaks had difficulty eating food, and that year, many finches with small beaks survived and inherited their characteristic to their offsprings.

This case of the evolution of finch beaks is an example of evolution by natural selection. This process involves the five processes of evolution that we previously talked about – non-random mating, genetic drift, mutation, gene flow, and natural selection.