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 territory, singing intermittently, but the female may establish a separate individual wintering range until pair formation begins in the early spring. During migration, the song thrush travels mainly at night with a strong and direct flight action. It flies in loose flocks which cross the sea on a broad front rather than concentrating at short crossings (as occurs in the migration of large soaring birds), and calls frequently to maintain contact. Migration may start as early as late August in the most easterly and northerly parts of the range, but the majority of birds, with shorter distances to cover, head