Birds live where they have enough food and nesting places. In the garden with tall trees and lush grass, overgrown with bushes, many convenient places for nests and grabs a variety of insects, seeds and fruits. Here in the spring there will be young growth. If in the garden they often cut lawns, cut bushes and trees, burn fallen leaves, destroy weeds, and in the fight against insect pests spray plants with poisonous chemicals, the conditions of life of birds so deteriorate that they are unlikely to remain here.
Now on Earth there are about 9000 species of birds. Unfortunately, scientists can not always unequivocally say which birds should be referred to a certain species, so it is difficult to accurately count the number of already known species. For example, blackbirds differ in their appearance: in Turkey they are large and their color is somewhat faded; On the Canary Islands thrus are smaller and darker in Germany; Individuals living in India, gray with a dark cap.
Are blackbirds with gray plumage from India and black or brown from Europe to the same species or different? Individuals of one species of any animals, not just birds, give fertile offspring (not just offspring, but prolific). Different species usually do not mate. Kindred species, for example black and singing thrushes, although they live in the neighborhood, are always looking for a partner of their own kind to create a family. Just to determine the species belonging to different birds living in one locality. If the birds are externally similar, but live far apart, it can not be predicted if they would mate, if they were in the same locality.