The diminutive Willow warbler is a small bird from the Leaf Warbler family Phylloscopidae which contains 80 species. Willow warblers are primarily insectivorous and are energetic, constantly moving birds that dart their tree and hedgerow habitats. They possess soft and subtle green plumage with a pale green-grey back, wings and tail with a pale grey stomach that has a slight yellow tinge.
10.5cm to 11.5cm
16cm to 22cm
7g to 12g
A small bird of some 11cm in length, the Willow warbler is primarily soft olive green with a green-grey back and wings. Their breast has a yellow tinge, and they also have a rather distinctive stripe above the eye.
Willow Warblers have reasonably long and pointy beaks for the genus and they have large primary feathers which are likely developed to support their migratory behaviours. Willow warblers are aesthetically similar to Chiffchaffs and they can be notoriously hard to tell apart by looks alone.
Close up of a Willow Warbler
Willow Warblers are small birds measuring 11 to 12.5 cm long (4.3 to 5 inches). Most are quite slender in build. They are amongst the smaller of the Leaf warblers, similarly sized to their lookalike the Chiffchaff. Their wingspan is around 19cm (7.2in) on average.
Willow Warblers weigh around 10 grams (0.35 oz) on average.
The scientific name of the Willow warbler is Phylloscopus trochilus and there are three subspecies; Phylloscopus trochilus acredula, Phylloscopus trochilus trochilus and Phylloscopus trochilus yakutensis.
Close up of a perched Willow Warbler
In the upper Northern hemisphere, Willow Warblers are very common with some 34 million breeding pairs estimated to be living in Europe alone. Perhaps unsurprisingly then, competition between Willow warblers can be fierce. The males are especially territorial and frequently fight other birds that cross their territorial boundaries.
They also typically maintain primary and secondary breeding territories as the males are frequently polygamous. Once their young grow, fledge and become independent, Willow warblers and most other Leaf warblers become more gregarious and frequently join mixed flocks.
There is little data on the life expectancy of the Willow Warbler but it’s estimated to range between 1 to 4 years which is around average for a bird of their size.
Willow Warbler on thistle bush
Globally, Willow Warblers are currently defined as a species of least concern, meaning there is no pressing risk to their overall population. With over 34 million breeding pairs spread over much of Europe and an estimated 10 to 100 million further pairs distributed across Russia, the Willow warbler is a plentiful species.
In the UK, Willow Warbler populations are decreasing and they’re now listed as an Amber List species.
Willow Warblers are primarily insectivorous but will consume some, albeit limited plant material. They mainly consume small bugs and flies like lacewings, damselflies, spiders, ants and snails.
Insect eggs also form a large part of their diet. Insects are caught mainly from the tree canopy, but may also be hunted in the tree canopy or on the ground.
Willow Warbler with an insect
There is some conflicting information as to whether Willow Warblers are monogamous or polygamous, but they likely don’t form lifelong bonds and the male is often observed to be polygamous.
The distinctively domed, enclosed and substantial nest of the Willow Warbler is usually built densely by low-lying foliage, or on the ground. They will also nest some 4 to 8m above the ground if a dense bush or other foliage is available. Willow warblers nest primarily in woodlands, forests and other densely foliaged environments where insect populations are also dense, and often stay within reach of water.
Willow Warbler nest with chicks
The female Willow Warbler generally lays around 4 to 9 eggs per clutch and will lay 1 to 2 clutches a year on average.
Willow Warbler eggs are very small - 3 eggs likely weigh no more than a one penny piece. They’re generally white and shiny with reddish-brown freckles across the base of the egg.
The literary definition of the word ‘warbler’ itself is a melodic sequence. Willow warblers, like all warblers, are named as such because they are capable of melodic songs.
Their song is mainly composed of short chirps and ascending and descending scales of notes. The pitch of the Willow warbler song is perhaps lower than other birds of similar size.
A calling Willow Warbler
Female Willow warblers do sing, but it is the males who sing most enthusiastically throughout the breeding season as they try to attract and woo their mates. Songs are also used in territorial behaviour, primarily by males to alert others of their presence and where the boundaries of their territories lie.
Willow Warblers tend to choose dense, wooded foliage that is densely packed with insect life. Their nests are typically built in covert locations under dense foliage such as that contained in low-lying shrubs and hedgerows. They are often found near birch, willow and alder trees which tend to grow near rivers and lakes.
Willow Warbler about to take off
Willow warblers are much more common in Scandinavia, Russia and Northern Europe than they are in Western Europe. They appear on European shores around April after wintering primarily in Western Africa.
Willow warblers are common across the entirety of northern Europe and Russia, stretching all the way to eastern Siberia in the east and the western tip of Ireland in the west. They live as far north as the arctic tundra. Willow warblers are much less common in southern Europe.
Yes, Willow warblers migrate every year after breeding in Europe. They head to Africa and primarily settle on the west coast of the continent, just south of the Sahara, though some populations are found in central and even eastern Africa too.
Willow warblers breed in their temperate northern latitude habitats before wintering in Africa. They leave in July through to September and return sometime in March or April. Their migratory patterns are complex and will often involve stopovers in southwest Asia or the Mediterranean.
Willow Warbler perched in a tree with nesting material
Willow warblers winter primarily in Africa, leaving the UK somewhere between July and September and returning in around April to breed.
An elusive reedbed-dwelling songbird, the moustached warbler breeds in marshlands across southern Europe. Rare reports of breeding in the UK do exist, although no sightings of the species have been confirmed in Britain since the 1940s.
This small but long tailed, large headed warbler, is a resident of the Balearic Islands in the western Mediterranean where it is common, although is not present on the island of Menorca.
Widespread across southern Europe and North Africa, Sardinian warblers are known for their chattering, fast-paced song, commonly heard throughout Mediterranean areas.
Yellow-browed warblers are rare winter visitors to the UK, with fewer than 30 birds arriving after their breeding season in Siberia has drawn to a close. A few hundred sightings of these tiny migrants are also recorded in passage each year, along the east coast of Scotland, and eastern and southern coasts of England.
Wood warblers are tuneful breeding visitors, arriving in British woodlands from April onwards. Well hidden in their preferred tree-filled landscapes, their bright yellow breast makes them easily distinguishable from other similar warbler species.
Whitethroats are active warblers that can be seen and heard in hedgerows around Britain during spring and summer months, as they raise their young and busily forage for insects. Each autumn, they depart for wintering grounds in sub-Saharan Africa, returning in April to breed once more.
Widespread and common breeding visitors to the UK, sedge warblers arrive on marshlands and reedbeds in April, and spend up to 6 months on British soil (or wetlands, to be more accurate), raising their young, before preparing for lengthy migrations to wintering grounds in sub-Saharan Africa each autumn.
Savi’s warblers are long-distance migratory songbirds, breeding across continental Europe and north-west Africa, and spending winters in West Africa. Extremely rare in the UK, with only around 5 breeding pairs a year, Savi’s warblers are mostly found in marshlands and habitats with dense reed cover.
A wetland songbird with a rather unremarkable appearance, the reed warbler is a spring visitor to the UK, raising young in wetland reedbeds across England and Wales before returning to African wintering grounds at the end of the summer.
Seen only very occasionally in the UK, the marsh warbler is a long-distance migrant, breeding across central and eastern Europe and spending winters in south-eastern Africa. Sightings in Britain are limited to coastal areas, where up to only around 8 pairs are recorded as breeding each year.
Smaller and less common than the closely related whitethroat, the Lesser Whitethroat, is a hard-to-spot breeding visitor to the UK, due to its unremarkable plumage and favoured habitats of dense hedgerow vegetation.
A well-camouflaged visitor to grasslands and reedbeds, grasshopper warblers arrive in Britain to breed each spring. You may stand a better chance of hearing one than actually getting a sighting, as their secretive nature of creeping through vegetation makes them almost impossible to spot.
Garden warblers are unobtrusive, inconspicuous songbirds that are most commonly found foraging in woodlands during spring and summer months, before heading south to wintering grounds in Africa each autumn.
Mainly confined to lowland heaths in southern England, the Dartford warbler is an elusive little resident breeder with distinctive plumage and physical characteristics.
Until recently this small, solitary, old world leaf warbler was classified as being a member of the family Sylviidae, but following extensive research and reclassification, now falls within the family of Phylloscopidae.
A particularly hard-to-spot bush warbler, the Cetti’s warbler bred in Britain for the first time in the 1970s and now is an established species, with an expanded breeding range in wetland reedbeds around the southern, eastern and south-western coasts of England, and the south and north coasts of Wales.
Within its range and to differentiate it from other similar species, it is often referred to as an Eurasian Blackcap. This sexually dichromatic, stocky little warbler, is a member of the genus Sylvia and is sometimes nicknamed the Northern Nightingale due to its beautiful and frequent song.
Aquatic warblers are rare and temporary migrants to parts of southern England each autumn, en-route from their breeding grounds in Poland, Ukraine and Belarus to their winter territories in West Africa. Only around 40 sightings are reported each year, with the species classed as vulnerable and in decline.
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