Coastal Silver-stiletto vs Common Eider

Acrosathe annulata compared with Somateria mollissima

Key Differences

• Coastal Silver-stiletto is Least Concern while Common Eider is Near Threatened.

Taxonomic Classification

Rank	Coastal Silver-stiletto	Common Eider
Kingdom same	Animalia (Animals)	Animalia (Animals)
Phylum	Arthropoda (Arthropods)	Chordata (Chordates)
Class	Insecta (Insects)	Aves (Birds)
Order	Diptera (Diptera)	Anseriformes (Anseriformes)
Family	Therevidae	Anatidae
Genus	Acrosathe	Somateria
Species	Acrosathe annulata	Somateria mollissima

Evolutionary Relationship

Coastal Silver-stiletto and Common Eider share a common ancestor at the Kingdom level: Animalia. (Animals)

Conservation Status

Coastal Silver-stiletto

LC — Least Concern

Common Eider

NT — Near Threatened

Physical Characteristics

Attribute	Coastal Silver-stiletto	Common Eider
Diet	—	—
Average Lifespan	—	—
Average Length	—	—
Average Weight	—	—

Habitat & Geographic Range

Coastal Silver-stiletto

Habitat

Typically found in virtually all terrestrial and freshwater habitats.

Range

Distributed across Belgium, Denmark, Norway, and Sweden.

Common Eider

Habitat

Typically found in various aerial, terrestrial, and aquatic environments.

Range

Found across Europe (5 countries) and North America (United States). Listed as Near Threatened, this species requires ongoing monitoring to prevent population decline.

Coastal Silver-stiletto

Coastal silver stiletto (Acrosathe annulata) is a slender robber fly in the family Therevidae, native to northwestern Europe, including the United Kingdom, France, the Netherlands, Belgium, and Scandinavia. Adults are found on coastal sand dunes and sandy heathland, where they perch on bare sand to ambush small flying insects. Stiletto flies in the family Therevidae are characterised by a slender body, long pointed abdomen, and predatory habits; adults prey on a variety of small dipterans and other flying insects during warm, sunny periods. Larvae develop in sandy soil, where they are also predatory, feeding on other invertebrate larvae. Acrosathe annulata is a habitat specialist restricted to open, sandy coastal habitats with sparse vegetation—environments that have declined substantially across northwestern Europe due to dune stabilisation, recreational disturbance, and the cessation of traditional dune management. The IUCN lists it as Least Concern, though regional conservation bodies in the United Kingdom have flagged population declines. It is considered an indicator of high-quality coastal sand dune habitats and is monitored through national invertebrate surveys.

Common Eider

Common Eider (Somateria mollissima) is classified as Near Threatened (NT) on the IUCN Red List. Close to qualifying as threatened, with populations that may become vulnerable without conservation action.

Shared Countries

Both species can be found in 4 countries:

🇧🇪 Belgium 🇩🇰 Denmark 🇳🇴 Norway 🇸🇪 Sweden