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"
Song thrush introduced bird species, and the song thrush also damages commercial fruit crops in that country. As an introduced species it has no legal protection in New Zealand, and can be killed at any time. The song thrush typically nests in forest with good undergrowth and nearby more open areas, and in western Europe also uses gardens and parks. It breeds up to the tree-line, reaching 2,200 metres (7,250 ft) in Switzerland. The island subspecies "T. p. hebridensis" breeds in more open country, including heathland, and in the east of the song thrush's Eurasian range, the nominate subspecies is restricted to