As swallowtail season approaches here at Strumpshaw Fen, our volunteer Jenna explains why these magnificent butterflies are so special, how we create the perfect home for them at Strumpshaw and how you can take action for nature and help your local butterflies.
Swallowtail butterfly perched on a pink orchid flower in grassland. The butterfly is striped with black and yellow, with a line of blue spots ending in one red spot across each hind wing. Its hind wings are pointed like a swallow’s tail. Photo Credit: Matthew Wilkinson
Swallowtails are special not only because they are strikingly beautiful but also because they are one of Britain’s rarest butterflies. Historically, their range was much larger as fens covered more of the country, but they are now restricted to the Norfolk Broads. You can read more about swallowtails on the www.bbc.co.uk/norfolk/your/extra/swallowtail . A similar trend of declines is being seen in many UK species; the State of Nature 2019 report found that butterfly numbers are down by 17% since 1970 – so every action we take to look after our butterflies counts!
Big hungry caterpillar! Swallowtail larvae feed almost solely on milk parsley. This swallowtail caterpillar is climbing up a green milk parsley plant stem. The caterpillar is green with black and orange stripes. Photo Credit: Matthew Wilkinson
Swallowtail caterpillars feed almost exclusively on the foliage of milk parsley plants. Milk parsley is also fussy about where it grows, preferring high-quality fen habitat – this is where our habitat management team at Strumpshaw come in.
Fen Warden Matthew surveying milk parsley plants. Standing amid tall reeds and pointing up at the white, umbrella-shaped flower clusters of a milk parsley plant. Photo Credit: Jonathan Woolley
The fen is managed to maintain a specific community of plants that provide excellent habitats for all our star species, including bitterns, bearded reedlings and marsh harriers, as well as our swallowtails. To do this, we mow many areas of the fen on a four-year rotation while our highland cattle graze other areas for us, and some areas are left alone. This mimics the historical land uses of the fen as closely as possible, with a few tweaks (such as four years rather than one year between mowing) to optimise the habitat for wildlife.
The team also keeps a close eye on the salt levels in the fen water and manages this by taking water off the reserve via the sluices when the river floods. This is because species such as milk parsley are not salt-tolerant and would disappear if the reserve were to transition to a salt marsh habitat. For this reason, sea-level rise and seasonal flooding is of growing concern for the conservation of swallowtails and their habitats in the Norfolk Broads. Creating new fens further inland and translocating species are possible options for the future.
Habitat maintenance in the fen - Reedbed under blue sky. Some areas of the reed have been mowed and five long-handled forks are standing in the ground, one with a pair of gloves resting on the handle, as the habitat management volunteers take a well earned break! Photo Credit: Jenna Hatch
Fortunately, attracting butterflies to your garden, balcony or window box is much simpler than looking after our swallowtails! From planting for caterpillars to giving tired butterflies an autumn boost with a feast of banana, there are plenty of easy ideas on the RSPB’s new Nature on Your Doorstep webpages. If you are inspired to survey the butterflies in your local patch, you can contribute to Butterfly Conservation’s scientific work by taking part in their recording and monitoring schemes this summer – no garden required!
Photo Credit: Bradley Hatch
You never know which species will arrive in your garden! This photo shows a rather dishevelled-looking swallowtail butterfly feeding on a pink foxglove flower in my parents garden!
We would love you to show us how you help butterflies and you can do this via our social media pages here: Facebook: https://www.facebook.com/RSPBStrumpshaw and Twitter: https://twitter.com/RSPB_Strumpshaw
Or get involved in our community pages here: Nature on Your Doorstep webpages