Bog-trotting. 4. Crowle Moor

For today's recce we stray just across the Yorkshire border into North Lincolnshire, to visit Crowle Moor. This reserve is a section of the largest lowland raised bog in England, the Humberhead Peatlands National Nature Reserve. The NNR is composed of Thorne, Hatfield, Goole and Crowle Moors, what remains of an extensive, raised bog, a thick and growing dome of peat. Manual extraction of peat for domestic use in the XIX century was at low scale and superficial allowed for the quick recovery of the Sphagnum mosses, but  drainage, commercial extraction of peat and land reclamation or 'warping' degraded the peat bog. After decades of local opposition to the destruction of the bog, environmental activism and the documentation of the presence of over 4,000 species of insects in the site, commercial peat extraction stopped in sections until finally stopped completely in 2001. By that time, and despite its degraded status, it was clear that the Humberhead Peatlands held a lot of biodiversity and it was declared a National Nature reserve, SSSI and SCA. Crowle Moor is located on the south eastern side of the area and managed by the Lincolnshire Wildlife trust and North Lincolnshire Council. Currently drainage is carefully managed in 'cells' to keep the water table raised so that the peat bog can recover. It is fiendishly complex work as the drainage network is extensive and the extraction of peat means that surface levels differ across the site.

It was mostly overcast, but warm, again, we were spared most of the biting insects! After meeting our hosts for the day, aka bogtrotter and Ted, local naturalists that know the moor inside out, we start walking along the track towards an area of wet heath where Bog Bush-crickets have been seen.

This piling is a dam holding water in the moor to keep the bog moist, part of the conservation efforts for the site.

Today we have our acoustic receiver, the little red device attached to a phone, which will allow us to record bush-crickets by detecting their almost ultrasonic calls. There were many conehead nymphs and other bush-crickets calling.

A tall wall of Bracken bounded the track before it opened up.

It wasn't long before Ted called he had seen the first Bog Bush-cricket of the day, a female late instar nymph.

Round-leaved Sundew.

Stepping just out of the track was quite treacherous, with very boggy and uneven terrain. Hopefully, the acoustic device will allow us to record bush-crickets across a wide transect following the track itself.
We found several more Bog Bush-crickets near this single track, and Sarah could even hear them calling, what a superpower! We noticed Bog Bush-crickets were with one exception present on Purple Moorgrass, away from Cross-leaved Heath, which was quite different from our previous trips.

Roesel Bush-cricket.

The competition

Soon we found out that Roesel's have also colonised Crowle, and found this calling male (above) not very far from where we spotted the Bog Bush-crickets. Roesel's are undergoing a dramatic range expansion across the UK. Both species might compete where they meet and there is research in southern Sweden showing that Roesel's might outcompete Bog Bush-crickets, with Bog bush-crickets declining in areas where Roesel's were experimentally introduced. We will follow this up with acoustic surveys to assess the extent to which Roesel's are expanding into wet heathland.

After lunch in the car park, including a delicious slice of fruit cake baked by bogtrotter, we moved to the southern side of the reserve. There, after walking all round we found no signs of Bog bush-crickets, but Roesel's were all along the main path along a ditch and also at the entrance of the south end. The habitat was spot on, with even the delightful Bog Rosemary present along with cross-leaved heath and purple moorgrass. It was late afternoon and overcast, so conditions might not have been ideal for them. 

Wall Brown.

A very large long-winged Roesel's female on the entrance to the south area of the reserve.

Black-tailed Skimmer.

Bog Rosemary.

Cross-leaved Heath.

Emerald Damselfly?

An Easter Fox Spider on the track.

More information

Berggren, A., and M. Low. 2004. Exclusion of the native bog bush-cricket Metrioptera brachyptera by the currently invading Roesel’s bush-cricket Metrioptera roeseli." Entomologisk Tidskrift 125 (2004): 125-32.

Rotherham, Ian D. 2010. Yorkshire's Forgotten Fenlands. Wharncliffe Books. 181 pp.

Bog-trotting. 3. Strensall Common

My first visit to this large reserve, as a recce for our upcoming Bog Bush-cricket acoustic survey. Sarah and I arrive around 8:15. It is mostly overcast, with light cloud cover, and a brief light shower, but it is warm and humid, which means we get to see a lot of insects. Fortunately, the water level has subsided from what it sounded like a very flooded heath earlier in the year. There were only a couple of tricky spots to cross, and I managed the trip with (mostly) dry socks in my trainers. It was a quiet walk, with just a dog walker seen near the car park, and possibly two naturalists further into the reserve. 

Strensall Common is a designated Special Area of Conservation (SAC) and SSSI. It is one of the largest areas of lowland heath in England, at 570 ha, and one of the best quality wet and dry heath sites in the UK. It has highly diverse habitas, with a mosaic of wet and dry heath, grassland, woodland, scrub, bogs and pools. The woodland is open and mostly pine and birch and there is a lot of natural regeneration of both, with a spread of tree ages, giving it a very natural woodland look, with plenty of heathland underneath. The site survival in such good condition stems from its military use, the MOD bought the common in 1884 for military training purposes. It is an active training site, and the area used for firing is fenced off and out of bounds during exercises, which was the case today. The area outside of this is still quite large, and that was our roughly circular route around the eastern side of the common.

One of the padlocked gates into the training area, closed to visitors today, hopefully we'll be able to visit in the future.

Round-leaved Sundew.

The habitat is managed with sheep and cattle grazing in summer and autumn. Species of conservation concern include Nightjar, Woodlark, Pillwort, Marsh Gentian, Pond Mud Snail and it is the only site in England for the Dark Bordered Beauty Moth.

Heath with naturally regenerating pine.

We start walking along a footpath towards the west of the car park and soon we see the first patch of wet heath, and it is not long until we find the first Bog Bush-cricket, a female late instar nymph, which bodes well for the day. The Cross-leaved Heath is plentiful and flowering, with many stems in bud, the extremely wet year has probably created ideal conditions for this species.

As we walk, we come across these rounded depressions with steps on the pea (photo above), indicating old manual peat cuttings. This is also the origin of several ponds and boggy areas in the reserve, together with tank ruts.

The Bog Bush-crickets

We end up counting 20 bog bush crickets, most found on or very close to Cross-leaved Heath, with Purple Moorgrass growing nearby, a few on a patch of lush Purple Moorgrass. We notice a sex bias towards females, with few males found. Adults, both males and females were already present, but there were areas with late instar nymphs. We follow a method of walking slowly amongst the heath, paying attention to any movement. The relatively still and not too warm conditions definitely help, with the bush-crickets more sluggish than otherwise they would have been and their movement more easy to spot.

The first Bog Bush-cricket of the day, a female nymph.

Female nymph bog bush cricket on purple moorgrass and cross-leaved heath.

An green form adult female Bog Bush-cricket on a large clump of Purple Moorgrass.

Adult male Bog bush-cricket on Purple Moorgrass.

Other Orthoptera

Strensall is a great Yorkshire site for Orthoptera, they are diverse and abundant. We recorded Common Green Grasshopper, Meadow Grasshopper, Mottled Grasshopper and Common Groundhopper, in addition to the Bog Bush-cricket.

Mottled Grasshopper.

Common Groundhopper.

Dragonflies and Damselflies

We recorded Common, Ruddy and Black Darter, Blue-tailed Damselfly, undetermined blue Damselfly and a Brown Hawker. I was quite pleased with the Black Darter, a species I don't often come across.

Male Black Darter

Other invertebrates

We recorded Green-veined White, Small and Large Skipper, Ringlet, Gatekeeper and Small Heath. A number of Funnel-web Spiders were seen, a species that appears to be expanding it's range northwards. One caught an unfortunate mottled grasshopper we disturbed. A Bog Hoverfly, Sericomya silentis, was seen, but was too fast for a photo. The weather conditions kept the number of biting insects low, so I am pleased to report two horsefly records and two mosquito bites, which is quite reasonable for this time of year.

The distinctive Funnel-web Spider, Agelena labyrinthica on her web.

The unfortunate Mottled Grasshopper with her spider predator.

The stunning Band-eyed Brown Horse Fly, Tabanus bromius.

Birds

A disappointing bird list, but probably normal given the time of year. Of note was a family of Stonechats near the car park.

More information

Strensall Common YWT.

Freshwater habitats Trust.

Strensall Common Site Improvement plan.