Westhern Marsh Harrier

Circus aeruginosus

Order: Accipitriformes
Family: Accipitridae
Presence in the Strait: Seasonal
Abundance: common
Protection in Spain: Special protection (List)
In Spanish: Aguilucho lagunero occidental

36% of its open observations in the area are from September.

Photograph: Artem Kuznetsov, CC BY, vía iNaturalist

Length: 48–55 cm
Wingspan: 110–125 cm
Weight: 550–675 g

Presence in the Strait

Common winter visitor to wetlands (>35). Abundant breeder until La Janda dried out, there are recent records that indicate that it may breed again in the near future.

Identification

Like all harriers, soar and glide with their narrow wings in “V” position and a long tail. The male is brown and grey with black wing-tips. The female is dark brown with cream crown and leading edge of wings. Juveniles are female-like, but with only cream on crown.

Movements

Very prolonged migration; the first arrive at the end of July and leave the area at the end of May (>300 post. migr.). Peaks in 2nd hf. March and 2nd hf. September.

Ring recoveries

Germany (4), Holland (3), Sweden (3) and United Kingdom (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

36 %

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: 25 February 1966
Latest record: 5 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: LC · Least concern · breeding
Global Red List (IUCN): LC · Least concern

Annex I of the Birds Directive

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

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

Germany4
Netherlands3
Sweden3
United Kingdom1

See the journey on the map

Same genus in the Strait

Montagu´s Harrier43–50 cm · Seasonal · overlapping size
Northern Harrier43–50 cm · Seasonal · overlapping size
Pallid Harrier40–50 cm · Seasonal · 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: Accipitriformes
Family: Accipitridae
GBIF taxon key: 2480482

Sources

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

Westhern Marsh Harrier

Presence in the Strait

Identification

Movements

Ring recoveries

Gallery