Description
The blackcap is a mainly grey warbler with distinct male and female plumages. The nominate subspecies is about 13 cm long with a 7–8 cm wing length. The weight is typically 16–25 g, but can be up to 31 g for birds preparing to migrate. The adult male has olive-grey upperparts, other than a paler grey nape and a neat black cap on the head. The underparts are light grey, becoming silvery white on the chin, throat and upper breast. The tail is dark grey, with an olive tint to the outer edge of each feather. The bill and long legs are grey, and the iris is reddish brown.
The female resembles the male, but has a reddish-brown cap and a slightly browner tone to the grey of the upperparts. Juveniles are similar to the female, but their upperparts have a slight rufous tinge, and the breast and flanks have a more olive tone; young males have a darker brown cap than their female counterparts.
Blackcaps have a complete moult in their breeding areas in August and September prior to migration. Some birds, typically those migrating the greatest distances, have a further partial moult between December and March. Juveniles replace their loosely structured body feathers with adult plumage, starting earlier, but taking longer to complete, than the adults.
The male’s song is a rich musical warbling, often ending in a loud high-pitched crescendo, which is given in bursts of up to 30 seconds. The song is repeated for about two-and-a-half minutes, with a short pause before each repetition.
The song’s introduction is like that of other blackcaps, but the final warbling part is a simple alternation between two notes, as in a great tit’s call but more fluting. The main song is confusable with that of the garden warbler, but it is slightly higher pitched than in that species, more broken into discrete song segments, and less mellow. Both species have a quiet subsong, a muted version of the full song, which is even harder to separate.
The blackcap occasionally mimics the song of other birds, the most frequently copied including the garden warbler and the common nightingale. The main call is a hard tac-tac, like stones knocking together, and other vocalisations include a squeaking sweet alarm, and a low-pitched trill similar to that of a garden warbler.
The male’s song is a rich musical warbling, often ending in a loud high-pitched crescendo, which is given in bursts of up to 30 seconds. The song is repeated for about two-and-a-half minutes, with a short pause before each repetition.
The song’s introduction is like that of other blackcaps, but the final warbling part is a simple alternation between two notes, as in a great tit’s call but more fluting. The main song is confusable with that of the garden warbler, but it is slightly higher pitched than in that species, more broken into discrete song segments, and less mellow. Both species have a quiet subsong, a muted version of the full song, which is even harder to separate.
The blackcap occasionally mimics the song of other birds, the most frequently copied including the garden warbler and the common nightingale. The main call is a hard tac-tac, like stones knocking together, and other vocalisations include a squeaking sweet alarm, and a low-pitched trill similar to that of a garden warbler.
Distribution and Habitat
The blackcap is distributed in Northwest Africa, East Asia, Western Siberia, the Atlantic coast to the Ob River valley, Asia Minor and the Caucasus. It is found throughout Europe, except in the northern parts of the Scandinavian Peninsula. In Norway, its range reaches 69 ° north latitude, in the European part of Russia – up to the 63rd parallel, and in the Ob River valley – up to 64 °. The total number of the great black-headed nettle is estimated at about 10 million individuals, with Europe inhabited by 75-94% of all birds.
The blackcap is found both in the plains and in the mountainous regions up to 1700 m above sea level. Inhabits parks and gardens in settlements, riparian forests and rare and rich in dense undergrowth deciduous forests. European forms show a clear preference for spruce forests. It prefers humid areas and is often found near water bodies.
It arrives in Bulgaria in April and departs in October. It is found throughout the country, except for the deforested agricultural areas of the Thracian lowlands, the Danube plain and Dobrudja.
The species generally winters in the southern Iberian Peninsula, the Mediterranean and North Africa near the equator. It is also very rare in sub-Saharan Africa. Spring migration begins in March, and autumn – in September and October. In recent years, it has been noticed that more and more birds remain to winter in Europe. Birds from the northern and eastern parts of the continent are completely migratory. During a flight, a bird can stay on average between 4-8 days in one place before continuing its journey. Birds of all ages of both sexes migrate together.
Feeding
The blackcap feeds mainly on insects during the breeding season, then switches to fruit in late summer, the change being triggered by an internal biological rhythm. When migrants arrive on their territories they initially take berries, pollen and nectar if there are insufficient insects available, then soon switch to their preferred diet. They mainly pick prey off foliage and twigs, but may occasionally hover, flycatch or feed on the ground. Blackcaps eat a wide range of invertebrate prey, although aphids are particularly important early in the season, and flies, beetles and caterpillars are also taken in large numbers. Small snails are swallowed whole, since the shell is a source of calcium for the bird’s eggs. Chicks are mainly fed soft-bodied insects, fruit only if invertebrates are scarce.
In July, the diet switches increasingly to fruit. The protein needed for egg-laying and for the chicks to grow is replaced by fruit sugar which helps the birds to fatten for migration. Aphids are still taken while they are available, since they often contain sugars from the plant sap on which they feed. Blackcaps eat a wide range of small fruit, and squeeze out any seeds on a branch before consuming the pulp. This technique makes them an important propagator of mistletoe. The mistle thrush, which also favours that plant, is less beneficial since it tends to crush the seeds. Although any suitable fruit may be eaten, some have seasonal or local importance; elder makes up a large proportion of the diet of northern birds preparing for migration, and energy-rich olives and lentisc are favoured by blackcaps wintering in the Mediterranean.
Blackcaps defend good winter food sources in the wild, and at garden feeding stations they repel competitors as large as starlings and blackbirds. Birds occasionally become tame enough to feed from the hand.
Breeding
When male blackcaps return to their breeding areas, they establish a territory. Adults that have previously bred return to the site they have used in previous summers, whereas inexperienced birds either wander until they find a suitable area, or establish a very large initial territory which contracts under pressure from neighbours. Territorial boundaries are established initially by loud singing, performed while the male displays with his crown raised, tail fanned and slow wingbeats. This display is followed, if necessary, by a chase, often leading to a fight.
Blackcaps first breed when they are one year old, and are mainly monogamous, although both sexes may sometimes deviate from this. A male attracts a female to his territory through song and a display involving raising the black crown feathers, fluffing the tail, slow wingbeats, and a short flapping flight. He also builds one or more simple nests (cock nests), usually near his songpost. The final nest, which may be one of the cock nests or built from scratch, is a neat cup of roots, stems and grasses lined with fine material such as hair. The nest is typically 5.5 cm deep and 10 cm across, and is built in the cover of bramble, scrubs or trees. It is constructed mainly by the female, and may be up to 4.5 m above the ground, although lower than 1 m is more typical.The clutch is typically 4–6 eggs , which are usually buff with grey and brown blotches and a few dark brown spots.
The eggs are incubated for an average of 11 days (range 10–16). Both adults incubate, although only the female stays on the nest at night. The chicks are altricial, hatching naked and with closed eyes, and are fed by both parents. They fledge about 11–12 days after hatching, leaving the nest shortly before they are able to fly. They are assisted with feeding for a further two or three weeks. If the nest is threatened, the non-incubating bird gives an alarm call so that the sitting parent and chicks stay still and quiet. A male blackcap may mob a potential predator, or try to lure it away with disjointed runs and flaps on the ground.
Conservation Status
The distribution area of the blackcaps is extremely wide. In addition, the number of birds is slowly increasing and the population size is extremely large. This moves the bird away from the vulnerability threshold and according to the criteria for range and number of birds, the species is considered non-endangered.
