A significant increase in the numbers of rare Swallowtail Butterfly this year has seen the Broads specific-species reach its highest recorded population levels since 2011.
The good weather experienced over the past two years and proper management of the fens have been attributed to their rise in numbers.
Alan Dawson, the transect coordinator of the Norfolk branch of Butterfly Conservation said when Swallowtail numbers were good, it meant management of the fens was working and milk parsley, the plant on which they lay their eggs and eat when caterpillars, was doing well.
He said: 'Without all the work put in by Broads Authority, RSPB and Natural England this environment would be rapidly lost.'
The Broads Authority, biodiversity partners and landowners together successfully achieved their goal of restoring 400 hectares of open fen in 2010, a figure which was comparable with its extent in 1946.
Broads Authority senior ecologist Andrea Kelly said: 'This summer provided good weather conditions for flying butterflies and some days you could see literally hundreds of these big yellow and black butterflies zooming over the rich fen vegetation finding mates and searching for a drink of nectar.'
Weather conditions have played an important role in the Swallowtail success story.
The growth of the milk parsley, the flight pattern of the Swallowtails and the Swallowtail pupae lying attached to the base of reed stems can all be effected by poor weather conditions.
The good weather of 2016 and 2017 has given the butterflies an opportunity to thrive without the threat of harsh conditions.
The Swallowtail used to appear in late May and June, but in recent years a sizable second brood in late summer has given them a second chance at increasing their numbers.
The butterfly data is collected by volunteers who walk set routes, which are known as transects.
The transects run through nature reserves and volunteers record butterfly numbers as they pass through them.
The transect scheme is a national effort, forming a major part of the UK Butterfly Monitoring Scheme administered jointly by Butterfly Conservation, The Centre for Ecology and Hydrology and the British Trust for Ornithology.
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