page_title: Common blackbird
section_title: Natural threats
hierarchical_section_title: Common blackbird / Behaviour and ecology / Natural threats
context_page_description: The common blackbird is a species of true thrush. It is also called the Eurasian blackbird, or simply the blackbird where this does not lead to confusion with a similar-looking local species. It breeds in Europe, Asiatic Russia, and North Africa, and has been introduced to Australia and New Zealand. It has a number of subspecies across its large range; a few of the Asian subspecies are sometimes considered to be full species. Depending on latitude, the common blackbird may be resident, partially migratory, or fully migratory.
  The adult male of the common blackbird, which is found throughout most of Europe, is all black except for a yellow eye-ring and bill and has a rich, melodious song; the adult female and juvenile have mainly dark brown plumage. This species breeds in woods and gardens, building a neat, mud-lined, cup-shaped nest. It is omnivorous, eating a wide range of insects, earthworms, berries, and fruits.
  Both sexes are territorial on the breeding grounds, with distinctive threat displays, but are more gregarious during migration and in wintering areas. Pairs stay in their territory throughout the year where the climate is sufficiently temperate.
context_section_description: Near human habitation the main predator of the common blackbird is the domestic cat, with newly fledged young especially vulnerable. Foxes and predatory birds, such as the sparrowhawk and other accipiters, also take this species when the opportunity arises. However, there is little direct evidence to show that either predation of the adult blackbirds or loss of the eggs and chicks to corvids, such as the European magpie or Eurasian jay, decrease population numbers.
  This species is occasionally a host of parasitic cuckoos, such as the common cuckoo (Cuculus canorus), but this is minimal because the common blackbird recognizes the adult of the parasitic species and its non-mimetic eggs. In the UK, only three nests of 59,770 examined (0.005%) contained cuckoo eggs. The introduced merula blackbird in New Zealand, where the cuckoo does not occur, has, over the past 130 years, lost the ability to recognize the adult common cuckoo but still rejects non-mimetic eggs.
  As with other passerine birds, parasites are common. Intestinal parasites were found in 88% of common blackbirds, most frequently Isospora and Capillaria species. and more than 80% had haematozoan parasites (Leucocytozoon, Plasmodium, Haemoproteus and Trypanosoma species).
  Common blackbirds spend much of their time looking for food on the ground where they can become infested with ticks, which are external parasites that most commonly attach to the head of a blackbird. In France, 74% of rural blackbirds were found to be infested with Ixodes ticks, whereas, only 2% of blackbirds living in urban habitats were infested. This is partly because it is more difficult for ticks to find another host on lawns and gardens in urban areas than in uncultivated rural areas, and partly because ticks are likely to be commoner in rural areas, where a variety of tick hosts, such as foxes, deer and boar, are more numerous. Although ixodid ticks can transmit pathogenic viruses and bacteria, and are known to transmit Borrelia bacteria to birds, there is no evidence that this affects the fitness of blackbirds except when they are exhausted and run down after migration.
  The common blackbird is one of a number of species which has unihemispheric slow-wave sleep. One hemisphere of the brain is effectively asleep, while a low-voltage EEG, characteristic of wakefulness, is present in the other. The benefit of this is that the bird can rest in areas of high predation or during long migratory flights, but still retain a degree of alertness.
caption: A male attempting to distract a male kestrel close to its nest
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