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
Common black hawk distinctive piping "spink-speenk-speenk-spink-spink-spink". The common black hawk is protected in the far north of its range (in the USA) under the Migratory Bird Treaty Act of 1918. Common black hawk The common black hawk ("Buteogallus anthracinus") is a bird of prey in the family Accipitridae, which also includes the eagles, hawks, and Old World vultures. It formerly included the Cuban black-hawk ("Buteogallus gundlachii") as a subspecies. The mangrove black hawk, traditionally considered a distinct species, is now generally considered a subspecies, "B. a. subtilis", of the common black-hawk. The adult common black-hawk is long and weighs on average. It has