A drought on the Galapagos island of Daphne Major in 1977 limited the amount of tiny seeds accessible to finches, resulting in the deaths of numerous small-beaked finches. This resulted in an increase in the average beak size of finches between 1976 and 1978. The large beaks are better at extracting nutrients from larger seeds.
This evolutionary response to a lack of choice available food sources is called "cannibalism driving evolution". As the population becomes dominated by individuals with larger beaks, they can better compete for food, thus prolonging their own lives. This effect has been observed in other animals including lions, lemmings, and gerbils. In these cases, cannibalism has led to the evolution of bigger bodies or brains because they provide additional benefits for the individual that consume them.
The finches on Daphne Major were studied by Richard Bowler in 1979. He found that the large beak phenotype was dominant, indicating that it must provide some advantage over smaller beaks. However many of the larger beaked birds were also less fit than others in the population, suggesting that there may be costs associated with having a large beak that prevent this trait from evolving further.
A severe drought in 1977 wiped out many of Daphne's finches, laying the groundwork for the Grants' first significant finding. As a result, giant finches and their progeny thrived during the drought, resulting in a long-term rise in the average size of the birds. The Grants had witnessed evolution at work. After the drought ended, finch sizes returned to normal -- but because there were so many larger birds around, the smaller ones were less likely to survive.
Finches are small birds found all over the world. There are 13 different species of finch. They are famous for being able to adapt to different habitats by using their beaks to eat plants that other animals would find too tough or poisonous to eat. This ability has helped some species evolve into different varieties with different colors and patterns. For example, there are two varieties of grosbeak finch: one with a red beak and one with a yellow beak.
Finches have been on Daphne since at least 1959 when James and Eleanor Grant first came to study them. At that time, there were only three species of finch on the island -- goldfinch, greenfinch, and American goldrush. Since then, more than 20 different species have been identified by scientists visiting the island.
Daphne is an island off the coast of New Hampshire in America. The island is home to many unique organisms due to its isolated location and lack of human influence.
The huge ground finch landed on the tiny Galapagos island of Daphne, just east of San Salvador, in 1982. Since then, the medium ground finch, a long-time Daphne inhabitant, has acquired a smaller beak, presumably as a result of direct competition for food with the larger bird. This evolutionary change happened quickly: scientists estimate that the small beak was developed within five years of the large finch arriving on Daphne.
Darwin's finches are famous for their ability to adapt to changing conditions. By testing different types of food when they can't find anything else, the birds on Daphne have shown that they will eat seeds from certain plants and not others. This means that there is a chance that other species of plants without nuts or seeds might be eaten by the birds on Daphne. Scientists think that this possibility may have led to the evolution of new plants with small seeds on other islands where the large ground finch has spread its wings.
In conclusion, the large ground finch brought with it foreign seeds that caused plants with small seeds to evolve on Daphne. These small seeds weren't enough to support the large ground finch, so it moved on to other islands where it helped cause the evolution of new plants with small seeds.
Daphne major is a suitable research site since the finches have few predators or competition. Because they can crack open larger seeds, medium-sized finches with broader beaks might benefit from other food sources. Because the smaller-beaked birds were unable to do so, they died of malnutrition.
Finches live in colonies where the female provides food for her mate and their young. The two types of finches found on Daphne Major are the Carolina chickadee and the American goldfinch. Before Europeans arrived, there were hundreds of thousands of these birds on Daphne Major and elsewhere in the Caribbean. Since then, only small populations of both species have survived. Why aren't more being born? Probably because humans kill most of the bird's main food source, the carob tree. The wood from these trees is used for furniture making and chariots in ancient Egypt!
People first came to the Caribbean Islands in 1503 when Christopher Columbus visited. He was looking for India but instead found America. When he returned to Europe, he reported that he had found a new continent and people started calling it "The New World". After this initial visit, no one has been back to the Caribbean until now. In 1632, Spanish explorers led by Juan de Bermudez searched out Daphne Major and other islands in the Caribbean. They were looking for gold but didn't find any.