Common cuckoo lay eggs that better imitate the host's eggs, the host species adapts and is more able to distinguish the cuckoo egg. A study of 248 common cuckoo and host eggs demonstrated that female cuckoos that parasitised common redstart nests laid eggs that matched better than those that targeted dunnocks. Spectroscopy was used to model how the host species saw the cuckoo eggs. Cuckoos that target dunnock nests lay white, brown-speckled eggs, in contrast to the dunnock's own blue eggs. The theory suggests that common redstarts have been parasitised by common cuckoos for longer, and so have evolved to be better
Bird reserve Habitat) is an international agreement to protect wetlands, with special focus on aquatic birds. In Sweden it is the County administrative boards of Sweden and the Environmental Protection Agency that selects which areas are to be designated as bird reserves. Among the noted areas are Tåkern, Lake Hornborga, the southern part of Öland and Getterön. There are approximately 50 Ramsar areas in Sweden, and around 530 SPA areas where the latter comprises almost . Bird reserve A bird reserve (also called ornithological reserve) is a wildlife refuge designed to protect bird species. Like other wildlife refuges, the main goal of