The garden warbler (Sylvia borin) is a common and widespread small bird that breeds in most of Europe and in the Palearctic to western Siberia. It is a plain, long-winged and long-tailed typical warbler with brown upperparts and dull white underparts; the sexes are similar and juveniles resemble the adults. Its two subspecies differ only slightly and interbreed where their ranges overlap. Due to its lack of distinguishing features, this species can be confused with a number of other unstreaked warblers. The garden warbler's rich melodic song is similar to that of the blackcap, its closest relative, which competes with it for territory when nesting in the same woodland.

The preferred breeding habitat in Eurasia is open woodland with dense low cover for nesting; despite its name, gardens are rarely occupied by this small passerine bird. The clutch of four or five blotched cream or white eggs is laid in a robust cup-shaped nest built near the ground and concealed by dense vegetation. The eggs are incubated for 11–12 days. The chicks are altricial, hatching naked and with closed eyes, and are fed by both parents. They fledge about 10 days after hatching. Only about a quarter of young birds survive their first year. The garden warbler is strongly migratory, wintering in sub-Saharan Africa. A wide range of habitats are used in Africa, but closed forest and treeless Sahel are both shunned. Insects are the main food in the breeding season, although fruit predominates when birds are fattening prior to migration, figs being a particular favourite where available. These warblers have a mixed diet of insects and fruit in their African wintering grounds.

The garden warbler is hunted by Eurasian sparrowhawks and domestic cats, and its eggs and nestlings are taken by a variety of mammalian and avian predators. It may be host to various fleas, mites and internal parasites, and it is a host of the common cuckoo, a brood parasite. The large and fairly stable numbers and huge range of the garden warbler mean that it is classed as least concern by the International Union for Conservation of Nature. Despite a small population decline in much of its European range, the bird's breeding distribution is expanding northwards in Scandinavia.

Taxonomy

The genus Sylvia, the typical warblers, forms part of a large family of Old World warblers, the Sylviidae. Fossils from France show that the genus dates back at least 20 million years. The garden warbler and its nearest relative, the blackcap, are an ancient species pair which diverged very early from the rest of the genus, 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 Sylviid species except the lesser whitethroat and greater 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.

The garden warbler was given the binomial name Motacilla borin by the Dutch naturalist Pieter Boddaert in 1783. The current genus name is from Modern Latin silvia, a woodland nymph, related to silva, a wood. The specific borin is derived from a local name for the bird in the Genoa area of Italy; it derives from the Latin bos, ox, because the warbler was believed to accompany oxen.

In the 19th and early 20th centuries there was some uncertainty as to the correct authority for this species. Various names were used including Sylvia salicaria Linnaeus 1766, and Sylvia simplex Latham 1787. Confusingly, the species was also known as Sylvia hortensis Bechstein 1802, where hortensis is the specific epithet of the western Orphean warbler.

There are two recognised subspecies.

  • Sylvia borin borin (Boddaert, 1783), the nominate subspecies, breeds in western, northern and central Europe to Finland, central Poland, western Hungary and Bosnia.
  • S. b. woodwardi (Sharpe, 1877), named for Sharpe's collaborator Bernard Barham Woodward, breeds in eastern Europe and temperate Asia east to western Siberia.

Intermediate birds occur where the recognised forms meet and interbreed, and have sometimes been given subspecies status, including S. b. kreczmeri in Poland and S. b. pateffi in Bulgaria, but these are not generally accepted as valid taxa. It is a plain, long-winged and long-tailed bird with unstreaked olive-brown upperparts and dull white underparts. The most frequent call of the garden warbler is a sharp kek-kek, which is repeated rapidly when the bird is alarmed. A quiet rasping tchurr-r-r-r resembling the main call of the common whitethroat is also sometimes heard. Subsong may be heard on the wintering grounds in Africa, developing into the full song in March and April prior to the return to Europe. During their journey, they can metabolise not only body fat but also up to 19% of their breast and leg muscles and 39% of their digestive tract. Many birds pause for a few days to feed after the desert crossing before continuing further south. S. b. woodwardi winters in eastern and southern Africa. This warbler has occurred as a vagrant in Afghanistan, Djibouti, Iceland, São Tomé and Príncipe, Somalia, Yemen, Svalbard, Jan Mayen and Madeira. 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. However, it appears more likely from later studies that segregation of sympatric species, other than the blackcap and garden warbler, is due to subtle differences in habitat preferences rather than interspecies aggression. There are typically 3–9 territories per hectare (1.2–3.6 per acre), but in prime habitat, such as moist willow or birch woodland or young deciduous regrowth, there may be more than 10 pairs per hectare (4 per acre).

A male attracts a female to his territory through song and a display which involves rapid wing beating while perched. He will also build a number of simple nests (cock's nests) to show to his mate, although only rarely will she complete the structure, usually starting afresh.

upright|thumb|Painting of an egg

thumb|Cuculus canorus canorus in a clutch of Sylvia borin borin - [[MHNT]]

The first eggs are laid in late April in southern Germany, early May in northwest Europe, and late May in Finland. The season is prolonged with some birds nesting as late as July. The eggs are incubated for 11–12 days by both adults, 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 10 days after hatching (range 9–12), leaving the nest shortly before they are able to fly. One brood per year is normal, although a few second broods are known. Much greater ages, up to 24 years, have been recorded in captive garden warblers. Berries and other soft fruit are preferred, This predilection gives rise to the Italian beccafico (fig pecker) and Portuguese felosa-das-figueiras (fig-tree warbler) as names for this species.

In Africa, the warbler eats insects as well as berries, and the fruits of the introduced Spanish flag is a favourite where present. Unlike drier-habitat species like the common whitethroat, they leave from savanna rather than the treeless Sahel further north.

Fruit is normally picked by a perched bird, although there is a record of a mulberry fruit being taken in flight. Garden warblers often feed with conspecifics and other fruit-eating passerines. Over 35 plant species have been recorded as food for this warbler just in central Europe, with many additional species being consumed in the Mediterranean region and on the African wintering grounds. Eurasian jays and Eurasian magpies take the eggs and young of warblers, as do mammals such as stoats, weasels and squirrels. The garden warbler is a host of the common cuckoo, a brood parasite. The blackcap has a much lower level of parasitism than its relative because the cuckoo's eggs are often rejected.

External parasites of the garden warbler include the fleas Ceratophyllus gallinae and Dasypsyllus gallinulae and the mite Syringophilopsis borini, named after its host. Two species of protozoan parasites in the genus Isospora occur in garden warblers, I. sylvianthina and I. sylviae. Samples from two sites showed infection levels above 74% and 28% respectively for the two species. The extent of infection does not impact on the bird's body mass or the amount of body fat. Three strains of another protozoan, Haemoproteus parabelopolskyi are found only in the garden warbler, and form a monophyletic group. Seventeen further members of that group are found only in the blackcap, and another three occur in the African hill babbler, supporting the shared ancestry of the three bird species.

There has been a slight decline in numbers in Europe since 1980,

In culture

In his History of Animals, Aristotle considered that the garden warbler eventually metamorphosed into a blackcap. The composer Olivier Messiaen used the song of the garden warbler as the basis for his 1971 solo piano piece La fauvette des jardins, the title being the French name of the species. His Turangalîla-Symphonie, a major work inspired by the legend of Tristan and Iseult, has a summer garden scene as its sixth movement. This features the song of the warbler, along with those of the nightingale and blackbird.

The garden warbler is prized as a gastronomic delicacy in Mediterranean countries. French epicure Jean Anthelme Brillat-Savarin said of the warbler when cooked like ortolan bunting "if it were the size of a pheasant, it would be worth an acre of land". An Italian stuffed sardine dish sarde a beccafico derives its name from its supposed resemblance to the cooked birds, known in that country as beccafico, fig-pecker.

Old names for the garden warbler, such as strawsmear, small straw and haychat, are often derived from its choice of nesting material, although the commonest of the English folk names was "pettychaps". These names were often shared with other warblers including the blackcap, common whitethroat and common chiffchaff.

References

Cited texts

  • Garden warbler videos and photos on the Internet Bird Collection
  • Ageing and sexing (PDF; 1.8 MB) by Javier Blasco-Zumeta & Gerd-Michael Heinze
  • Feathers of garden warbler (Sylvia borin)
  • Garden warbler - Species text in The Atlas of Southern African Birds