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 level below the threshold required for global conservation concern (i.e., a reduction in numbers of more than 30% in ten years or three generations) and the IUCN Red List categorises this species as of "Least Concern". In Great Britain and the Netherlands, there has been a more than 50% decline in population, and the song thrush is included in regional Red Lists. The decreases are greatest in farmlands (73% since the mid-1970s) and believed to be due to changes in agricultural practices in recent decades. The precise reasons for the decline are not known but may be related to the