Fen Bog YWT


Site Description

Recorders:  Graham Featherstone                       Distance:   1352m                      Walk Time Approx 45mins

Fen Bog is a fen and moorland nature reserve situated between the summits of Tom Cross Rigg and Crag Stone Rigg and the summit of the NYM railway.  It takes the form of a long curving piece of land that is bounded at both ends by moorland streams. The 19 hectare site comprises of two main sections; the main valley mire and the higher ground leading down to it from the parking area which is primarily wet heath and moorland and is separately fenced from the rest of the site. 


S1 from near the car park   and then down to teh entrance style and is quiet good for many grassalnd species. S2 enter heathland and Green hairstreak is found. S3 -S4 along the east rim of the bog is heath and is the best area to see Small Pearl-bordered Fritillary  as well as Small Heath abound along with Emperor moth. S5-S6 enter the bog where the Large Heath is found. 

Results 2022

County wide 2023 results reflect  the 2022 and  2023 spring drought with Small Tortoiseshell and Peacock nearly halved for the second year against their 5 year average. Red Admiral arrived in force in July and took advantage of soft nettle growth of the rains and had their best year ever. Drought sensitive species on thin soils were badly hit,  particularly Dark -green Fritillary and Northern Brown Argus but also Ringlet, Green-viened White and Small Heath.  Less drought affected species along with the hottest June on record built even more on gains last year leading to Comma, Brimstone, Holly Blue and most Browns  having a fantastic year reaching all time highs. A increase of 9% overall was mostly due to sheer numbers of Meadow Browns and Gatekeepers ment 2023 nearly pipped 2014 as best year in modern times.  Most noticeable was the large differeces between mositure retaining mineral soils of the valleys and thin, dry limestone or sandy soils. A large number of damp grassland, hedgerow and woodland  dominated sites benefitted hugely with 3 sites seeing more than 50% increase . A smaller number of thin, chalky, sandy or craggy sites did badly some down up to 25%.

Fen Bog has had a torrid year with wildfire breaking out burning off teh bog area and surrounding and has had a very big influence on results along with last years hot weather some  things have boomed amonst the embers.  Total numbers were 30% down which is high but not unusual  on upland dry sites but still he pooreset year since 2015.  Smal Copper and Common Blue seem to be quick to respond to the more open conditions and likely their foodplant have taken advantage of the flush of nutrients from the fire.  Unfortunately no  Smal Pearl -bordered Fritillary or Large Heath were seen on transect but one LH was seen off transect and we hope they survive. 

Transect reports

Results 2022

Somewhat down on the recent average similar to other sites . The species trends however were very much the reverse of the rest of the county!  The big losers in the county were the skippers and the vanessids but not here where they both boomed which might be related to this being a wet site and being somewhat cooler with the altitude, The browns were  down while elsewhere they were almost universally up.  A wandering marbled white was seen for teh fist time this year as it was a dispersal year for this species.