Swallowtail


It's swallowtail time! Despite the appalling weather the first brood of these classic Broadland butterflies are now on the wing. Having spent the winter as pupae secreted amongst the dense acres of last years reed chaff, these enigmatic and startlingly beautiful insects emerge in late May and early June to gracefully float around the waterlogged fens seeking nectar and a partner with whom to mate. The swallowtails we have here in Norfolk form a distinct race brittanicus which is slightly smaller and has subtle variations in wing pattern when compared against the continental race gorganus. However our pure-breds may soon have a real problem in that their cousins from across the English Channel seem to be getting a hold in south England and may soon move north to hybridise with our natives and therefore eradicate the form. I have mixed feelings about this. On the one hand there is no doubt that having something special living only in our region is a real boon to us all, enhancing the reputation of the Norfolk Broads as being a unique haven populated by rare creatures. Further, the need to conserve swallowtails has been a major factor in the drive to clean up the Broads, create and maintain pristine fen habitat and develop new reserves, all of which benefits not only the butterflies but a vast wealth of other wildlife. In addition swallowtails are a major tourist attraction and pull in visitors from all over the country who seek to catch a glimpse of this strong flying jewel in its only UK stronghold. But (there's always a but) on the other hand, the Norfolk population is vulnerable, primarily because the caterpillars are so fussy. They will only feed on milk parsley, an uncommon plant that is thinly distributed in wet fen habitat. Because of this the insects cannot expand their range and should we have a sea surge or some other drastic climatic event the population could be wiped out. No such restrictions apply to the Continental race which will breed anywhere and feed on all sorts of plants including carrot and wild angelica, a distinct advantage. If the continental butterflies really take hold we will most likely see them in our gardens on a regular basis and they will no doubt thrive. So what is better; a UK race of limited range, dependent on a single food plant, vulnerable and never likely to be common, or a hybridised race (which will effectively become the continental form) which will range widely, can utilise a number of food plants and will therefore become resilient and a familiar widespread sight? Not easy is it? But I don't suppose we need worry because it is really out of our hands; nature will have its way whatever we think. In matter of fact the hybridisation may already be happening. I saw swallowtail caterpillars feeding on wild angelica 5 years ago when I was managing the NWT Visitor Centre at Ranworth and those may well have had a more exotic origin either from captive bred insects or genuine colonists. Who knows?

Anyway, an afternoon trip to Strumpshaw Fen found me and a few other beaming admirers watching one of these gorgeous butterflies nectaring on the flowerbeds outside Reception. Here RSPB reserve staff have planted a swath of Dame's violet whose fragrant blooms proved irresistible to not only the newly emerged swallowtail but a range of other butterflies and bees. Apparently earlier in the day 6 swallowtails were using the area but I was quite content with this singleton since they are always a privilege to see. Other butterflies utilising this nectar source included brimstone, peacock and large white whilst a roosting dagger moth showed that the sweet liquid is also appreciated by the night shift.

 

Swallowtail

 

Brimstone

 

Peacock



Strumpshaw is crammed full of beautiful things and after having my fill of the swallowtail I strolled along the woodland trail and bumped into another one. I won't embarrass her by mentioning her name, but it was great to meet up with an old friend and have a good chat. Sadly after this delightfully sunny encounter the atmospheric conditions deteriorated appreciably. The strengthening wind and scudding cloud did little to stimulate wildlife to put its head or anything else above the parapet, so I sought refuge in Fen Hide to see if anything came close. Alone in this ageing structure, its groaning timbers and creaking joints lent a feeling of mild desolation to the vista of lowering cloud and billowing reeds. June? Sometimes hard to believe. Although bird activity above the protection of the reed bed was limited there was some activity in the more protected zone around the willow scrub. A wren loudly proclaimed his territory and periodically added a piece of grass to a nest he was building in a tangle of sedge, a lone willow warbler searched for insects higher in the same bush whilst a water rail screeched and squawked unseen and unabashed from the sanctuary of deep cover. Then, with the prospect of rain squalls approaching and the gloom descending, it was time to walk back to the car and leave this most prolific of nature reserves to its wonderful inhabitants both animal and human.

Wren


Willow Warbler

 

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