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 smash snails. The nestlings are mainly fed on animal food such as worms, slugs, snails and insect larvae. The grove Snail ("Cepaea nemoralis") is regularly eaten by the song thrush, and its polymorphic shell patterns have been suggested as evolutionary responses to reduce predation; however, song thrushes may not be the only selective force involved. The song thrush has an extensive range, estimated at 10 million square kilometres (3.8 million square miles), and a large population, with an estimated 40 to 71 million individuals in Europe alone. In the western Palaearctic, there is evidence of population decline, but at a