A brood parasite, such as a cuckoo, lays its eggs in the nests of other birds (known as "host birds") and leaves the host bird to raise the parasitic young. The cuckoo egg is often very similar in appearance to the host bird's eggs, which helps to prevent the host from detecting the foreign egg. Additionally, some cuckoos have evolved behavioural adaptations that help them avoid detection. For example, the Common Cuckoo (Cuculus canorus) has been known to eject the host bird's eggs from the nest before laying its own egg, and the Brown-headed Cowbird (Molothrus ater) will sometimes mimic the song of the host bird to gain access to the nest. Furthermore, some cuckoos have developed chemical defences that help them avoid detection by the host birds. For example, the Great Spotted Cuckoo (Clamator glandarius) produces a chemical that mimics the scent of the host bird's eggs, which helps to prevent the host from rejecting the foreign egg.