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Tanners Dam

Image of male Ruddy Darter by Ken Gartside

Author: Ken Gartside
Images: Ken Gartside, S. Rae and Scyrene

Casual observation of marshy habitat

Tanners Dam is a medium sized acidic moorland pond in a glorious moorland setting, but also near an industrial site in Greenfield, Saddleworth, West Yorkshire (VC63). It was created by a local mill as a water source but has been disused for over 50 years and since then fished for recreation.

It has a rich flora and fauna, being adjacent to wild moorland with abundant Heather and upland bog. It has some mature trees around the banks but also emergent vegetation at each end with sheep-grazed moorland meadow to one side containing Soft Rush and Creeping Thistle.

It is largely stony bottomed, with soft mud built up in the marshy shallow ends which have Yellow Flag, Yellow Water Lily and Great Reed Mace, with Marsh Pennywort, Marsh Woundwort, abundant Common Skullcap and some Sphagnum mosses in the damp banks.

It has been fished (Carp and other coarse fish) for many decades and was originally barren of emergent vegetation and bankside trees, but has been well managed and largely left to develop naturally. Whilst awaiting a knee operation, which prevented me from walking far, I made frequent visits over the summer months (it is conveniently close to home) to record invertebrate wildlife by photographs - and this casual monitoring has revealed some interesting marshland species, with some new to Saddleworth and the Northern Peak District area.

Dragonflies (Odonata)

Image of Brown Hawker ovipositing by Ken Gartside

Breeding evidence of egg laying was captured on film and video for Brown Hawker (Aeshna grandis). Six adults in flight were seen at once which is a high number for Saddleworth and is the first such site with multiple females ovipositing. The males appear to be highly territorial and have distinct niches on the less fished and vegetated side of the water.

Also breeding here, seen in cop, are Large Red (Pyrrhosoma nymphula), Common Darter (Sympetrum striolatum), Common Blue (Enallagma cyathigerum) and Blue-tailed Damselflies (Ischnura elegans). It's interesting to note only one Moorland Hawker (Aeshna juncea) was seen this year, with no Broad bodied Chasers (libellula depressa) at this site, both of which are locally common.

Besides male and female Common Darters (Sympetrum striolatum), a notable and exciting find was Ruddy Darter (Sympetrum sanguineum) - a first for Saddleworth. A single male was seen over 4 separate days hunting and sunbathing, even allowing closeup macro photographs.

Hover flies (Syrphidae)

Image of Ferdinandea cuprea by Ken Gartside

Very high numbers of damp rushy loving Hoverflies, Platycheirus granditarsus and Platycheirus rosarum were seen, plus Xylota segnis, Xylota sylvarum and the water breeding Helophilus pendulus (larvae are rat-tailed maggots). Another Saddleworth first, Ferdinandea cuprea was present on one occasion. This is normally a tree trunk sunbather, and larvae breed in sap runs, including Ash, which are present adjacent to the pond.

Syrphus ribesii and other Syrphus species, Dasysyrphus tricinctum, Episyrphus balteatus, Eristalis pertinax, Eristalis tenax and Eristalis nemorum and the so-called Moorland Hover, Sericomyia silentis mating were also noted.

Other flies (Diperta)

Image of Sargus flavipes by S. Rae

As expected, adult Snail killing or Marsh flies (Sciomyzidae) whose larvae are parasitic on water snails can be seen basking in sun on emergent Iris and Reeds. Sepedon sphegea, Tetanocera sp. and Pherbina coryleti, with nice netted wings were recorded.

Also seen were the Conopid fly (Sicus ferrugineus), Yellow-legged Centurion (Sargus flavipes), The rust fly (Imantimyia (Loxocera) albiseta) in good numbers, Pipunculidae, Tipula oleracea and other Craneflies and Sepsis punctum. The Tachinid fly (Eurithia anthophila) was also noted. Unidentified Muscidae and Calliphoridae were also seen, the latter no doubt attracted by nearby casualties of a sheep and Canada Goose. Many thanks to YNU's own Ian Andrews for help with some ID's on Facebook's Diptera site.

Crickets and grasshoppers (Orthoptera)

Image of a Slender ground-hopper by Ken Gartside

A notable find was Slender Ground-hopper (Tetrix subulata), similar to Grasshoppers but prefers damp places and is infrequently seen. This again is a first for Saddleworth. The Common Groundhopper (Tetrix undulata) was also briefly spotted but awaiting confirmation. Common Green Grasshopper (Omocestus viridulus) was noted as well. There will be more similar species.

Beetles (Coleoptera)

Image of a Reed Beetle by Scyrene

A Reed Beetle (Plateumaris discolor) was recorded on Flag Iris. Reed Beetles can be in different metallic colours, this one was brownish bronze. This species prefers wet acidic habitat, but may be a synonym of Plateumaris sericea – that issue isn't totally resolved it seems

Bees and wasps (Hymenoptera)

The Sawfly (Athalia scutellariae), thought probable only from photographs of adults, was found in small numbers. I intend to look for the distinctive larvae to be certain next year. These are mainly associated with Marsh Skullcap (Scutellaria galericulata) which is in abundance here. They are probably under-recorded, with only 31 records on the National Biodiversity Network (NBN). A Pemphredon sp, Sphecoid wasp and ichneumonid Itoplectis maculator were also seen and given probable identifications with help of the Facebook Hymenopterists forum.

Butterflies (Lepidoptera)

Small Copper, Large White, Green-veined White, Red Admiral, Speckled Wood and Large Skipper Butterflies were seen in the bankside grassland.

Overall conclusions

A habitat which initially appears to be fairly empty of interest with just a short look can be worth regular visits and careful monitoring which may well be rewarded by the unusual. Much remains to be discovered.

It is also a reflection of the benefits of marshland and wild reedbeds to biodiversity, particularly in the light of the scorching hot June and July we had in 2018, which appears to have affected some insect numbers, mentioned in Dipterists Forum Bulletin recently (No. 86).

It will be worth more casual and in-depth monitoring from spring onwards for a full year in 2019, not only for recording but also to see whether some species criteria for designation as a SBI via the local Ecology Unit might be met. This with a view to preserving the site, being particularly mindful of potential planning applications to meet modern housing targets.

Published: 28/03/2019

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