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 rich yellow background colour to the underparts. It is a partial migrant with some birds wintering in southern France and Iberia. This form intergrades with the nominate subspecies in central Europe, and with "T. p. hebridensis" in the Inner Hebrides and western Scotland, and in these areas birds show intermediate characteristics. Additional subspecies, such as "T. p. nataliae" of Siberia, proposed by the Russian Sergei Buturlin in 1929, are not widely accepted. The song thrush (as represented by the nominate subspecies "T. p. philomelos") is 20 to 23.5 centimetres (8 to 9.25 in) in length and weighs 50–107 grammes (1.8