The Eurasian blackcap (Sylvia atricapilla) is a bird usually known simply as the blackcap. It is a common and widespread typical warbler. It has mainly olive-grey upperparts and pale grey underparts, and differences across the five subspecies are small. Both sexes have a neat coloured cap to the head, black in the male and reddish-brown in the female. The male's typical song is a rich musical warbling, often ending in a loud high-pitched crescendo, but a simpler song is given in some isolated areas, such as valleys in the Alps. The blackcap's closest relative is the garden warbler, which looks quite different but has a similar song.
The blackcap breeds in much of Europe, western Asia and northwestern Africa, and its preferred habitat is mature deciduous woodland. The male holds a territory when breeding, which is defended against garden warblers as well as other blackcaps. The nest is a neat cup, built low in brambles or scrub, and the clutch is typically 4–6 mainly buff eggs, which hatch in about 11 days. The chicks fledge in 11–12 days, but are cared for by both adults for some time after leaving the nest. The blackcap is a partial migrant; birds from the colder areas of its range winter in scrub or trees in northwestern Europe, around the Mediterranean and in tropical Africa. Some birds from Germany and western continental Europe have adapted to spending the winter in gardens in Great Britain and Ireland. Insects are the main food in the breeding season, but, for the rest of the year, blackcaps survive primarily on small fruit. Garden birds also eat bread, fat and peanuts in winter.
Despite extensive hunting in Mediterranean countries and the natural hazards of predation and disease, the blackcap has been extending its range for several decades, and is classified by the International Union for Conservation of Nature as least concern. Its rich and varied song has led to it being described as the "mock nightingale" and it has featured in literature, films and music. In Messiaen's opera Saint François d'Assise, the saint is represented by themes based on the blackcap's song.
Taxonomy
The genus Sylvia, the typical warblers, forms part of a large family of Old World warblers, the Sylviidae. The blackcap and its nearest relative, the garden warbler, are an ancient species pair which diverged very early from the rest of the genus at between 12 and 16 million years ago. In the course of time, these two species have become sufficiently distinctive that they have been placed in separate subgenera, with the blackcap in subgenus Sylvia and the garden warbler in Epilais. These sister species have a breeding range which extends farther northeast than all other Sylvia species except the lesser whitethroat and common whitethroat. The nearest relatives of the garden warbler outside the sister group are believed to be the African hill babbler and Dohrn's thrush-babbler, both of which should probably be placed in Sylvia rather than their current genera, Pseudoalcippe and Horizorhinus respectively.
The blackcap was one of the many bird species originally described by Carl Linnaeus in his landmark 1758 10th edition of Systema Naturae, as Motacilla atricapilla. The current genus name is from Modern Latin silvia, a woodland sprite, related to silva, a wood. The species name, like the English name, refers to the male's black cap. Atricapilla is from the Latin ater, "black", and capillus, "hair (of the head)".
Fossils and subfossils of the blackcap have been found in a number of European countries; the oldest, dated to 1.2–1.0 million years ago, are from the Early Pleistocene of Bulgaria. Fossils from France show that the genus Sylvia dates back at least 20 million years.
Subspecies
{| style="width:60%;" class="wikitable"
! style="text-align:center; background:#d3d3a4;" colspan="4"|Subspecies
|-
!width=20% | Subspecies
!width=24% | Authority
!width=28% | Range
!width=28% | Comments
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| S. a. atricapilla
| Linnaeus, 1758
| Europe (except Mediterranean area), northwestern Asia; winters northwestern Europe south to tropical western Africa.
| The nominate subspecies.
|-
| S. a. gularis <br />(syn. S. a. atlantis)
| Alexander, 1898
| Breeds and winters Azores and Cape Verde
| Slightly shorter wing than nominate, greyer underparts and nape.
|-
| S. a. heineken<br /> (syn. S. a. obscura)
| (Jardine, 1830)
| Breeds and winters Madeira, Canary Islands, southwestern Iberia, perhaps Morocco, Algeria.
| Males are browner above than the nominate subspecies, females are more rufous above, olive below.
|-
| S. a. pauluccii
| Arrigoni degli Oddi, 1902
| Breeds and winters eastern Iberia, Italy, western Mediterranean islands, and perhaps Tunisia.
| Like nominate, but greyer above and darker below, white confined to centre of belly.
|-
| S. a. dammholzi
| Stresemann, 1928
| Breeds southwestern Asia and winters tropical eastern Africa.
| Like nominate, but longer-winged and paler.
|-
|}
The differences between subspecies are small, making subspecific boundaries hard to define, and the exact distribution of S. a. heineken is unclear, since birds from northwest Africa may be of this form. About 2% of male blackcaps on Madeira and the Azores are melanistic, with black plumage on the whole head and upper breast. Melanistic females are rarer, and are characterised by grey-brown underparts. This dark morph has also been recorded from the Canary Islands, but not from Cape Verde. The melanistic birds were formerly sometimes considered to be a distinct subspecies, S. a. obscura.
Description
thumb|Male S. a. heineken in the [[Canary Islands, Spain|alt=A male blackcap perched in a tree]]
The blackcap is a mainly grey warbler with distinct male and female plumages. The nominate subspecies is about long with a wing length.
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. Blackcaps breeding in the north of the range have an earlier and shorter post-juvenile moult than those further south, and cross-breeding of captive birds shows that the timing is genetically controlled.
Voice
220px|thumb|Song of male, Moscow
thumb|Song of a male, Surrey, England
thumb|Calls of a male, Surrey, England
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. In some geographically isolated areas, such as islands, peninsulas and valleys in the Alps, a simplified fluting song occurs, named the Leiern (drawling) song by the German ornithologists who first described it. 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, Wintering birds in Africa are quiet initially, but start singing in January or February prior to their return north.
Distribution and habitat
Distribution
Adult female in Sweden showing reddish brown cap|thumb|alt=A grey bird with a brown cap
The continental breeding range of the blackcap lies between the 14–30° July isotherms, and is occupied by the nominate subspecies, the other forms being restricted to islands or fringe areas in the Caucasus and eastern Iberia.
There is a migratory divide in Europe at longitude 10–11°E. Birds to the west of this line head southwest towards Iberia or West Africa, whereas populations to the east migrate to the eastern Mediterranean and on to East Africa. Cross-breeding in captivity of birds from the resident population on the Canary Islands with migratory blackcaps from Germany showed the urge to migrate is genetically controlled, the offspring showing intermediate behaviour in terms of restlessness at migration time. Similar experiments using birds from southern Germany and eastern Austria, on opposite sides of the migratory divide, demonstrated that the direction of migration is also genetically determined. Climate change appears to be affecting the migration pattern of the garden warbler and blackcap. Both are arriving in Europe earlier than previously, and blackcaps and juvenile (but not adult) garden warblers are departing nearly two weeks later than in the 1980s. Birds of both species are longer-winged and lighter than in the past, suggesting a longer migration as the breeding range expands northwards.
thumb|Left graph shows likelihood of individual blackcaps being seen in a garden plotted against date, right graph shows likelihood plotted against air temperature. where the blackcap was formerly just a summer visitor. Although the British climate is sub-optimal, compensatory factors include the ready availability of food, (particularly from [[bird feeder|bird tables), a shorter migration distance, and the avoidance of the Alps and the Sahara Desert.
It now appears that the wintering birds in the UK come from a much wider area than previously thought. The majority come from France, and some individuals come from as far away as Spain and Poland. The steady supply of winter food in gardens gives even Spanish-breeding birds an opportunity to put on weight quicker than in their home range.
A 2021 paper showed that blackcaps, particularly adults, wintering in Britain and Ireland showed high site fidelity and low movement between wintering sites, in contrast to blackcaps wintering in their traditional winter ranges. Adults that frequented gardens had better body condition, smaller fat stores, longer bills, and rounder wing tips. The bill and wing tip shapes reflected a more generalist diet than that of birds in traditional winter sites.
Blackcaps did not exclusively feed in gardens; visits were linked to harsher weather. Individuals generally stayed at garden sites until immediately before spring departure, and supplemental feeding may have benefits for winter survival, When preparing for migration, abundant supplemental food may allow blackcaps to attain better body condition and may facilitate earlier and more successful breeding attempts.
Habitat
Deciduous woodland is the preferred breeding habitat.|thumb|alt=A woodland glade
The blackcap's main breeding habitat is mature deciduous woodland, with good scrub cover below the trees. Other habitats, such as parks, large gardens and overgrown hedges, are used as long as they meet the essential requirements of tall trees for songposts and an established understory. Where other Sylvia warblers also breed, blackcaps tend to use taller trees than their relatives, preferably those with a good canopy, such as pedunculate oak. In prime habitat, breeding densities reach 100–200 pairs per square kilometre (250–500 pairs per square mile) in northern Europe, and 500–900 pairs per square kilometre (1,250–2,250 pairs per square mile) in Italy. Densities are much lower in poorer habitats such as conifer forests. Breeding occurs in Europe at altitudes up to .
Behaviour
Territory
upright=0.6|thumb|left|Eggs, Collection [[Museum Wiesbaden, Germany]]
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. The typical territory size in a French study was , but in insect-rich tall maquis in Gibraltar, the average was only . Females feed within a home range which may overlap other blackcap territories, and covers up to six times the area of the defended zone.
thumb|upright=0.75|The eggs normally take about 11 days to hatch.|alt=Two eggs in a cup-shaped nest
Sylvia warblers are unusual in that they vigorously defend their territories against other members of their genus as well as conspecifics. Blackcaps and garden warblers use identical habits in the same wood, yet aggressive interactions mean that their territories never overlap. Similar songs are a feature of the Sylvia warblers as a group, and it has been suggested that this promotes interspecific competition and helps to segregate territories between related species. It appears more likely from later studies that segregation of sympatric species, other than the blackcap and garden warbler, is due to subtle habitat preferences rather than interspecies aggression.
Breeding
thumb|Young chicks begging for food. These are still largely unfeathered.|alt=Three small chicks with open red mouths in a nest
thumb|Cuculus canorus bangsi in a clutch of Sylvia atricapilla – [[MHNT]]
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 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. The blackcap normally raises just one brood, but second nestings are sometimes recorded, particularly in the milder climate of the Mediterranean and the Atlantic islands; triple brooding has been observed once, the female laying a total of 23 eggs in the season.
Of eggs laid, 65–93% hatch successfully, and 75–92% of the chicks go on to fledge.