The male common blackbird defends its breeding territory by chasing away other males or performing a "bow and run" threat display. This consists of a short run followed by the bird raising its and bowing it with its tail dipped simultaneously. If male blackbirds do fight, it is usually brief and the intruder is quickly chased away. The female blackbird is also aggressive in the spring when competing with other females for a good nesting territory. Although fights are less frequent, they tend to be more violent. As long as there is food available in winter, both male and females will remain in the territory throughout the year, although they will occupy different areas. Migrants are more sociable, travelling in small flocks and feeding in loose groups in their wintering grounds. The flight of migrating birds comprises bursts of rapid wing beats interspersed with level or diving movement. This differs from both the normal, fast, agile flight of this species, as well as the dipping action of larger thrushes. Although the species is socially monogamous, there have been studies showing as much as 17% extra-pair paternity. The nominate
T. merula may commence breeding in March, but the eastern and Indian races start a month or more later. The introduced New Zealand birds begin nesting in August (late winter). Eggs of birds of the southern Indian races are paler than those from the northern subcontinent and Europe. The young are fed by their parents for up to three weeks after leaving the nest, and will follow the adults begging for food. If the female starts another nest, the male alone feeds the fledglings. and, based on data from
bird ringing, the oldest recorded age is 21 years and 10 months. File:Eurasian blackbird (Turdus merula) female with nesting material South Bruny.jpg|Female with nesting material File:Blackbird nest with 3 eggs.jpg|Eggs in a nest File:Turdus merula -England -chicks in nest-8 (2).jpg|Two chicks in a nest File:Blackbird Fledgelings 2020 a 60 fps.webm|Blackbird fledgelings being fed File:Male Turdus merula feeding chicks.ogv|Male feeding chicks File:02-Common Blackbird 1-Jan-2023 nX.webm|Common blackbird foraging in Norfolk, England File:Turdus merula (AU)-full.webm|A common blackbird eating figs near Toulouse, France File:Blackbird feeding.mpg|Feeding chick and removing faecal sac
Songs and calls In its native range in the
Northern Hemisphere, the first-year male common blackbird of the nominate race may start singing as early as late January in fine weather in order to establish a territory. This is followed in late March by the adult male. The male's song is a varied, melodious, low-pitched fluted warble sung from trees, rooftops and other elevated perches mainly in the period from March to June, sometimes into the beginning of July. It has a number of other calls, including an aggressive
seee, a
pook-pook-pook alarm for terrestrial predators like cats, and various
chink and
chook, chook vocalisations. The territorial male invariably gives
chink-chink calls in the evening in an attempt (usually unsuccessful) to deter other blackbirds from roosting in its territory overnight. Like other passerine birds, it has a thin high
seee alarm call for threats from
birds of prey since the sound is rapidly attenuated in vegetation, making the source difficult to locate. The nominate subspecies
T. m. merula is known to mimic sounds in the local environment, including the songs of other birds, as well as human-made sounds, such as whistling and car alarms.
Feeding , Switzerland The common blackbird is
omnivorous, eating a wide range of insects,
earthworms, seeds and berries. It feeds mainly on the ground, running and hopping in a start-stop-start manner. It pulls earthworms from the soil, usually finding them by sight but sometimes also by hearing, and searches through
leaf litter for other
invertebrates. Small
amphibians, lizards and, on rare occasions, small
mammals are also occasionally hunted. This species will also perch in bushes to take berries and collect
caterpillars and other active insects. 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 to
parasitic cuckoos, such as the
common cuckoo (
Cuculus canorus), but this is rare because the common blackbird recognises the adult and the
non-mimetic eggs of the parasitic species. 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. These are external parasites that most commonly attach to the head of a blackbird. 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 several species that exhibits
unihemispheric slow-wave sleep. In this state, one hemisphere of the brain is effectively asleep, while a low-voltage
EEG, characteristic of wakefulness, is present in the other. This allows the bird to rest in areas of high predation or during long migratory flights while retaining a degree of alertness. ==Status and conservation==