Species › Birds

Willow Warbler

Phylloscopus trochilus

Order: Passeriformes
Family: Phylloscopidae
Presence in the Strait: Migrant
Abundance: abundant
Protection in Spain: Special protection (List)
In Spanish: Mosquitero musical

49% of its open observations in the area are from September.

Photograph: Andreas Trepte, CC BY-SA 2.5, vía Wikimedia Commons

Length: 12 cm
Weight: 9 g

Presence in the Strait

Abundant migrant.

Identification

Green upperparts and yellow underparts. Differs from a Chiffchaff in its pale legs, conspicuous supercilium, longer wings and different wing-formula: 2nd primary normally between 5th and 6th or equal to the 6th.

Movements

Peaks in 2nd hf. April and 2nd hf. September.

Ring recoveries

United Kingdom (11), Sweden (4), Norway (3), Belgium (3), Denmark (2), Germany (1), Spain (1), France (1), Holland (1), Poland (1) and Russia (1).

Bioestrecho editorial text. Last revised: 8 September 2026.

Photographs from iNaturalist observations with the licence checked file by file. Those marked “Strait” were taken within the area; place and date are those of each observation.

Calendar in the Strait

49 %

Peak in September. Observations under CC0 or CC BY licences. The distribution also reflects observation effort.

Where it is seen

Open records from the atlas database, in cells of about 3.6 km. Opacity follows the square root of the count, and also reflects where people observe most.

See on the map

First open record: 28 April 1921
Latest record: 8 April 2026

The oldest and the most recent open observation in the extended area. A recent first observation does not mean the species is new: it means nobody had published it openly before.

Conservation

The catalogues, Andalusian and Spanish, are what binds; the Red Book assesses the Spanish population with IUCN criteria, and the global Red List is the context.

LCNTVUENCR

Andalusian Catalogue: Special protection (List)
Spanish Catalogue: Special protection (List)
Red Book of the Birds of Spain 2021: DD · Data deficient · breeding
Global Red List (IUCN): LC · Least concern

Andalusian Catalogue: Junta de Andalucía, list of 24 April 2025. Spanish Catalogue: MITECO, table of 30 June 2025. Red Book: SEO/BirdLife, 2021 (Annex I). IUCN: via GBIF, 6 September 2026. Red Book and IUCN categories are assessments; catalogue categories are legal obligations.

Phenology compared

Monthly distribution in proportion, by decade. It shows whether the passage is getting earlier or later.

1990–1999

2000–2009

2010–2026

Proportions, not totals: observation effort grew faster than any population.

Where they come from

29 birds ringed in other countries and recovered in the area.

United Kingdom11
Sweden4
Norway3
Belgium3
Denmark2
Germany1

See the journey on the map

Same genus in the Strait

Common Chiffchaff11–11 cm · Seasonal
Western Bonelli´s Warbler11–11 cm · Seasonal
Wood Warbler12.5–12.5 cm · Migrant
Arctic Warbler12–12 cm · Vagrant
Mountain Chiffchaff11–11 cm · Vagrant

Species of the same genus that also occur here, ordered by how close they are in size. Being relatives does not mean they are confused in the field, but that is where the doubts start: compare size and season.

Classification

Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Passeriformes
Family: Phylloscopidae
GBIF taxon key: 2493052

Sources

Distribution and calendar: Bioestrecho's own database, ingested from GBIF and OBIS
Photograph: Andreas Trepte, CC BY-SA 2.5, vía Wikimedia Commons
Taxonomy: GBIF backbone, pending WoRMS for marine taxa
Editorial text: written by Bioestrecho
Last revised: 8 September 2026

Willow Warbler

Presence in the Strait

Identification

Movements

Ring recoveries

Gallery