The Swallowtail’s breeding sites are restricted to the Norfolk Broads. The Swallowtail requires sites which have a vigorous growth of Milk Parsley – its favoured food plant - where it will lay its eggs on the tallest plants. They can usually be found at
NWT Hickling Broad, RSPB Strumpshaw Fen
and How Hill nature reserve
Any rising of water levels or increase in salinity will effect the growth of the Milk Parsley. However Milk Parsley has the potential to grow in other areas and will move if there is suitable habitat. Active management of fenland, where sedge is cut to allow other plants to grow, plays an important part in the survival of the swallowtail in Norfolk.
Occasionally migrant Swallowtails from the continent can be found in Southern Britain but these are a different sub-species (gorganus
) to those found in Norfolk (britannicus