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
Everything which is not forbidden is allowed forbidden is compulsory." This quote has been suggested as a principle of physics. The claim that “everything which is not fobidden is allowed” is a principle only of English law does not stand the test of reality. In fact, it is a common principle of liberal democracies. In Germany, it has constitutional rank under Art. 2(1) of the GG which protects the general freedom to act (Allgemeine Handlungsfreiheit), as demonstrated e.g. by the judgment of the Bundesverfassungsgericht known as “Reiten im Walde” (BVerfGE 80, 137). Everything which is not forbidden is allowed "Everything which is not forbidden is allowed" is