Black-headed Gull

Chroicocephalus ridibundus

Order: Charadriiformes
Family: Laridae
Presence in the Strait: Seasonal
Abundance: abundant
IUCN (global): LC · Least concern
In Spanish: Gaviota reidora

Photograph: Alexis Lours, CC BY, vía iNaturalist

Length: 38–44 cm
Wingspan: 94–105 cm
Weight: 250–325 g

Presence in the Strait

Abundant winter visitor to coasts and wetlands (>4,000) including a large number of summering birds.

Identification

Medium-sized gull with red bill and legs. In flight, dark grey underwing primaries with black tips on both sides and white leading edge to wing. Winter plumage includes black tip on bill, white head with bold dark ear and eye-spots; black head in summer plumage. Juveniles are similar to those of a Mediterranean Gull but with a different wing pattern and pale legs and bill.

Movements

Peaks in 2nd hf. February and 2nd hf. October.

Ring recoveries

France (41), Holland (25), Finland (8), Belgium (7), Poland (1), Denmark (6), Sweden (6), Germany (5), Lithuania (4), United Kingdom (3), Switzerland (3), Czech Republic (3) and Russia (2).

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

15 %

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: 27 February 1932
Latest record: 7 January 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: Not included
Spanish Catalogue: Not included
Red Book of the Birds of Spain 2021: LC · Least concern · wintering or migrating
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

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

France41
Netherlands25
Finland8
Belgium7
Denmark6
Sweden6

See the journey on the map

Same genus in the Strait

Slender-billed Gull42–44 cm · Migrant · overlapping size

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: Charadriiformes
Family: Laridae
GBIF taxon key: 2481137

Sources

Distribution and calendar: Bioestrecho's own database, ingested from GBIF and OBIS
Photograph: Alexis Lours, CC BY, vía iNaturalist
Taxonomy: GBIF backbone, pending WoRMS for marine taxa
Editorial text: written by Bioestrecho
Last revised: 8 September 2026

Black-headed Gull

Presence in the Strait

Identification

Movements

Ring recoveries

Gallery