Swallowtail

A large, strong-flying butterfly restricted to the Norfolk Broads, although migrants are occasionally seen elsewhere. Pale yellow wings with black veins and blue margins.

This is one of our rarest and most spectacular butterflies. The British race britannicus is a specialist of wet fenland and is currently restricted to the Norfolk Broads. Here the adults can be seen flying powerfully over open fen vegetation, stopping to feed on flowers such as thistles and Ragged-Robin.

The butterfly probably declined within its range during the twentieth century but has benefited over the last few decades from conservation management aimed at increasing open fen vegetation. There are also scattered records of migrants of the continental race.

Size and Family

• Family: Swallowtails
• Size: Large
• Wing Span Range (male to female): 80-90mm

Conservation Status

• GB Red List (2022): Vulnerable
• Butterfly Conservation priority: Medium  
• Fully Protected in Great Britain under the 1981 Wildlife and Countryside Act
• European status: Not threatened                                

Caterpillar Foodplant

The native British race feeds solely on Milk-parsley (Peucedanum palustre). Occasional migrants of the continental race gorganus use a variety of umbellifers such as Wild Carrot (Daucus carota) and Wild Angelica (Angelica sylvestris). 

Lifecycle

Habitat

The British race britannicus breeds only in open fens and marshes that support vigorous growths of Milk-parsley. The butterfly prefers areas of mixed fen usually dominated by sedge, or sometimes reed, which are cut periodically and contain tall, prominent foodplants. The occasional migrants of gorganus can be found in almost any habitat but are most frequently seen on grassland near the south coast of England. 

Distribution

• Countries – England, Scotland, Wales and Ireland.
• The native UK populations are rare but stable and restricted to the Norfolk Broads.
• Abundance trend: 51% (1976-2019)
• Distribution trend: -27% (1996-2019)