Song thrush thrush recognizes the cuckoo's non-mimetic eggs. However, the song thrush does not demonstrate the same aggression toward the adult cuckoo that is shown by the blackbird. The introduced birds in New Zealand, where the cuckoo does not occur, have, over the past 130 years, retained the ability to recognise and reject non-mimetic eggs. Adult birds may be killed by cats, little owls and sparrowhawks, and eggs and nestlings are taken by magpies, jays, and, where present, grey squirrels. As with other passerine birds, parasites are common, and include endoparasites, such as the nematode "Splendidofilaria (Avifilaria) mavis" whose specific name "mavis"
Grey-cheeked thrush Grey-cheeked thrush The grey-cheeked thrush ("Catharus minimus") is a medium-sized thrush. This species is 15–17 cm in length, and has the white-dark-white underwing pattern characteristic of "Catharus" thrushes. It is a member of a close-knit group of migrant species together with the veery and Bicknell's thrush; it forms a cryptic species pair with the latter. The grey-cheeked thrush is all but indistinguishable from Bicknell's thrush except by its slightly larger size and different song. The two were formerly considered conspecific. Of all the American spotted thrushes, the grey-cheeked has the most northern breeding range. The grey-cheeked thrush is slightly larger