Origin of the granivorous beak?

The Darwinian theory of evolution goes from the emergence of species through natural selection out.

Not all birds are the same. Rather, there is a natural variation width. That means there are some birds with a very short beak, with others it is a little bigger. With others, it is even bigger, etc. This variation width becomes Variability called. It can be observed that the features are not randomly distributed. This means that birds with a larger beak have parents who also have larger beaks and they themselves also bear witness to descendants with larger beaks. Darwin concluded that the characteristics must be inheritable.

Let’s say you get the job to grow a new bird breed, e.g. canary finks, with a particularly strong beak. How would you do that? Quite simply, you’d look at your birds and then select the birds with the biggest beaks and pair them in a targeted manner. Among the descendants, you would select those with the greatest beaks again, etc. gradually forms through the targeted breeding a bird breed that shows the desired feature more and more strongly.

Such a readout also takes place in nature. In contrast to breeding, however, the selection is not carried out artificially by humans, but by the prevailing environmental conditions. In addition to the variability and the geneticity of the characteristics, Darwin also found that the resources available in nature (e.g. food, water) are limited and that more individuals can be born in each generation than survive by the resources available. He concluded that individuals must compete with each other for the resources. He called this competition fight for existence (struggle for life). Not all individuals are equally good in this competition. Some are randomly more competitive. Those birds with slightly more powerful beaks are better able to crack hard seeds. They can eat more in an environment where there are main hard seeds than food, and therefore survive longer, while their fellows with weaker beaks cannot crack and starve as well hard seeds. Darwin realized that those individuals in the struggle for existence are best cut off, which are by chance best adapted to their environment. Darwin called that the survival of the fittest (survival of the fittest). The most suitable individuals therefore have a greater survival success than the less well adapted. This means that they also have more time for reproduction and therefore, on average, testify to more descendants. A bird with a big beak may be able to raise three or four young people, while a bird with a small beak may only feed a boy or even if he dies, does not produce a young boy. Parents inherit their characteristics to their boys, i.e. the descendants of parents with a big beak will also have larger beaks on average. In their generation, those with the most powerful beaks will now survive best and continue to grow. Which individuals are best adapted depends on the environmental conditions. And this readout process, in which the best adapted individuals survive, is called natural selection.

Not only on the different islands, but also on the same island, different beak forms have formed by using different food.