page_title: Garden warbler
section_title: Breeding
hierarchical_section_title: Garden warbler / Behaviour / Breeding
caption_attribution_description: Garden Warbler (Sylvia borin), Bedfords park, Romford, Essex, UK
context_page_description: The garden warbler 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.
context_section_description: Garden warblers first breed when they are one year old, and are mainly monogamous, although the male at least may sometimes deviate from this. When males return to their breeding areas, they establish a territory. Sylvia warblers are unusual in that they vigorously defend their territories against other species in their genus as well as conspecifics. Blackcaps and garden warblers use identical habits in the same woods, 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. 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). Individual territories are similar in size to those of blackcaps at 0.2–0.76 ha (0.49–1.88 acres).
  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. The nest is concealed in vegetation, the nature of which depends on local availability. Rubus species are commonly used in temperate regions, with willow predominating in alpine valleys. Sometimes, particularly in stinging nettles, the nest may be built around a number of vertical stems, in the manner of a reed warbler. The nest is normally between 0.3 and 1.2 m (0.98 and 3.94 ft) above the ground, and very rarely higher than 2 m (6.6 ft). The nest is a cup of dry grass, moss and twigs, with a soft lining of finer plant material or hair. It is larger and heavier than a blackcap's nest, averaging 8.3 cm (3.3 in) high and 11.2 cm (4.4 in) wide with a cup 5.5 cm (2.2 in) deep and 6.3 cm (2.5 in) wide.
  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 clutch is typically four or five eggs (range two to six), which are usually whitish or buff with grey, purple and brown blotches. The average size of the egg is 20 mm × 15 mm (0.79 in × 0.59 in), and it weighs 2.2 g (0.078 oz), of which 6% is shell. 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. They are assisted with feeding for a further two weeks, and the family may stay together for a few days after that. The short incubation and fledging times may be a result of predation pressure, the rapid development of the chicks enabling them to leave the vulnerable nest as early as possible, even while still flightless. This avoids the possible loss of an entire brood, but means that the adults must provide food to the young for a significant period until they can fend for themselves. One brood per year is normal, although a few second broods are known.
  The southward migration starts in mid-July, with larger numbers departing in August and peaking in early September. Most adults have gone by mid-September, although juveniles may linger for another month.
  On average, just over 50% of breeding pairs are successful in producing at least one fledged young from a nest, with early breeding and low population density being factors increasing success. In the UK, more than 50% of the failures are due to predation and about 30% result from food shortages in bad weather. The annual survival rate is about 50% for adults and 26% for ju
caption: Singing male in England
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