Willow Warbler Bird Facts (Phylloscopus trochilus)

The Willow Warbler is a small, slender bird with olive-green upperparts and pale yellow underparts. It has a distinctive pale supercilium (eyebrow stripe) and a thin, pointed bill.

Males and females are virtually identical in appearance. Juveniles are similar to adults but have a slightly yellower overall plumage. The species shows little seasonal variation in its plumage.

The Willow Warbler can be found in Woodland habitats.

The Willow Warbler can be found in Garden habitats.

The Willow Warbler is not typically found in Wetland habitats.

The Willow Warbler is not typically found in Coastal habitats.

The Willow Warbler is not typically found in Urban habitats.

The Willow Warbler is not typically found in Farmland habitats.

The Willow Warbler is not typically found in Grassland habitats.

The Willow Warbler is not typically found in Desert habitats.

The Willow Warbler is not typically found in Tundra habitats.

The Willow Warbler is not typically found in Rainforest habitats.

The Willow Warbler is not typically found in Mountain habitats.

The Willow Warbler is not typically found in Savanna habitats.

Willow Warblers inhabit open woodlands, forest edges, and scrubland across much of Europe and western Asia. They prefer areas with birch, willow, and other deciduous trees mixed with undergrowth.

As long-distance migrants, they winter in sub-Saharan Africa. In the UK, they are widespread summer visitors, arriving in spring and departing by early autumn.

This map gives you a rough idea of where you might spot a Willow Warbler. The coloured areas show countries where these birds have been seen.

A few things to keep in mind:

Birds might not be everywhere in the coloured areas, for example, they may be present around the coast of that country
Where birds live can change with seasons and available food
This map is quite simple - it doesn't show exact locations

We're working on making our maps even better! Soon, we hope to show you:

More detailed maps for bigger countries, including state and region
How birds move around during different seasons

Species that appear infrequently (rare) and unpredictably outside their normal range

Canada Comoros Greenland India Japan Saint Helena, Ascension and Tristan da Cunha Seychelles Svalbard and Jan Mayen Islands

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Bird Attributes Explained

Our bird attributes system rates various aspects of a bird's capabilities on a scale of 0-100, based on data from field observations, scientific studies, and expert knowledge.

Attribute Categories:

Agility: Manoeuvrability, speed, and grace in flight or movement.
Strength: Physical power, often correlating with size and hunting abilities.
Adaptability: Ability to thrive in various environments or changing conditions.
Aggressiveness: Territorial behaviour and assertiveness, particularly during breeding seasons.
Endurance: Stamina, often seen in migration patterns or foraging behaviours.

Understanding the Ratings:

0-20: Very Low
21-40: Low
41-60: Average
61-80: High
81-100: Very High

Remember, these attributes are relative to other bird species and don't necessarily indicate superiority.

Agility

Reflects the bird's manoeuvrability, speed, and grace in flight or movement.

The Willow Warbler demonstrates remarkable agility, frequently hovering whilst foraging and adeptly flitting through foliage. Their active nature and ability to glean insects from leaves and branches, often in mid-air, indicates a high level of manoeuvrability and dexterity.

Strength

Indicates the bird's physical power, often correlating with size and hunting abilities.

As a small passerine weighing between 7-15 grams, the Willow Warbler possesses limited physical strength. However, their ability to undertake long-distance migrations suggests a degree of muscular endurance despite their diminutive size.

Adaptability

Represents the bird's ability to thrive in various environments or changing conditions.

Willow Warblers exhibit considerable adaptability, inhabiting various environments from sea level to 1,000 metres elevation. Their capacity to thrive in diverse habitats across Europe and western Asia, coupled with their successful long-distance migration to sub-Saharan Africa, demonstrates significant adaptive capabilities.

Aggressiveness

Measures the bird's territorial behaviour and assertiveness, particularly during breeding seasons.

Whilst not overtly aggressive, male Willow Warblers vigorously defend their territories during the breeding season through song and displays. This behaviour indicates a moderate level of aggression, primarily confined to territorial defence rather than general temperament.

Endurance

Reflects the bird's stamina, often seen in migration patterns or foraging behaviours.

The Willow Warbler's endurance is particularly noteworthy. Their ability to undertake annual migrations of up to 12,000 km (7,456 miles), coupled with their active foraging behaviour and the energy demands of breeding, suggests exceptional stamina for a bird of this size.

Willow Warblers primarily feed on small insects and spiders. They glean prey from leaves and branches, often hovering to reach items on the undersides of foliage. In autumn, they may supplement their diet with small berries and fruits to build fat reserves for migration.

Insect eggs also form a large part of their diet. Insects are caught mainly from the tree canopy but may also be hunted on the ground.

Willow Warblers are active and agile birds, often seen flitting through foliage in search of insects. They frequently hover while foraging, plucking prey from leaves.

During the breeding season, males establish and vigorously defend territories through song and displays.

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.

The Willow Warbler's song is a sweet, melodious warble that descends in pitch, often ending with a flourish. It can be described as a soft 'tsuu-ee-tsuu-ee-tsuu-ee-tsu-u-u'. Their call is a soft, plaintive 'hoo-eet' or 'hoo-ee'. The pitch is lower than birds of similar size.

Breeding occurs from April to July. Males attract females with their melodious songs and aerial displays. Pairs are monogamous during the breeding season.

The female builds a domed nest on or near the ground, hidden in dense vegetation. The nest is made of grass, leaves, and moss, lined with feathers. A typical clutch consists of 5-6 white eggs with reddish-brown spots.

Incubation lasts about 13-14 days, performed mainly by the female. Both parents feed the chicks, which fledge after 12-14 days. Pairs often raise two broods per season.

The Willow Warbler typically lives for 2 to 4 years, with a maximum recorded lifespan of 11.8 years.

Like all birds, lifespan can be affected by factors including predation, habitat quality, disease, and access to food sources.

While currently listed as Least Concern globally, Willow Warbler populations have declined in parts of Europe, including the UK. Habitat loss in both breeding and wintering grounds, as well as climate change impacts, are potential threats.

Conservation efforts focus on maintaining suitable breeding habitats.

Listen for their distinctive descending song in woodland edges and scrub
Look for their constant movement through foliage, often at eye level
Observe their habit of hovering briefly while foraging
In the UK, watch for their return in early spring (late March to April)

Main predators include sparrowhawks, domestic cats, and small mammals such as weasels and stoats. Nest predators may include jays, magpies, and rodents.

Willow Warblers can fly up to 12,000 km (7,456 miles) during their annual migration, one of the longest by any songbird.
They are one of the most numerous summer migrants in the UK, with over 2 million breeding pairs.
Despite their name, they are not closely related to New World warblers.

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