Hackney Main Marsh. Click on the photo to enlarge it. A SURVEY OF THE INVERTEBRATES OF HACKNEY MARSHES, 2007 by Neil Anderson November 2007 CONTENTS Introduction...............................................................4 Habitat Survey Map of Hackney Marshes................5 Methods....................................................................6 Species Lists: Birds................................................................9 Mammals.........................................................9 Insects............................................................10 Spiders...........................................................17 Molluscs........................................................19 Isopods..........................................................19 Amphipoda (Sandhoppers)............................20 General Comments.................................................21 Management Suggestions.......................................23 3 A SURVEY OF THE INVERTEBRATES OF HACKNEY MARSHES, 2007 by Neil Anderson INTRODUCTION Hackney Marshes comprise an extensive area (circa 170 hectares) of open, green land which constitutes the largest open space in the London Borough of Hackney. It forms part of the Lea Valley regional park. This area is dominated by amenity sports turf which is much used by the local community, particularly at weekends. The sports area does not support a wide diversity of invertebrates but can contain important numbers of a limited number of species, such as earthworm species and the larvae of such insects as crane flies (Tipulidae). This limited array of invertebrates do provide an important food resource for good numbers of birds, such as wintering gulls, Carrion Crows, Magpies, Starlings and a few pairs of Mistle Thrushes. Woodpigeons also use this area for feeding on seeds. Surrounding the football pitches are some valuable (for people and wildlife) corridors that allow a diverse range of fauna and flora to flourish. The tidal Old River Lea borders the eastern side of the Main Marsh and has a thriving fish population with its attendant avian predators, which indicate a healthy riverine ecosystem. Cormorants, Grey Herons and Kingfishers were regularly observed fishing here and a Little Egret was seen on one occasion. Outside the main breeding season there were small numbers of duck such as Mallard, Teal, Gadwall and Tufted Duck, feeding on seeds, aquatic vegetation and invertebrates. Mute Swans, Canada and Greylag Geese, Coots and Moorhens The tidal Old River Lea forms the east boundary of Hackney Main Marsh. also eke out a living here. Grey Wagtails were observed Click on the photo to enlarge it. feeding on insects at the water’s edge. Running along side the western perimeter is the Lea Navigation Canal – popular with boaters, walkers, cyclists and anglers. This supported a much smaller range of birds, but did have floating vegetation which provides suitable habitat for species such as the Red-eyed Damselfly, Erythromma najas. Common Frogs were also observed here. Within the boundaries formed by these waterways is a diverse mosaic of secondary woodland, scrub and neutral grassland habitats, which were the basis for this survey. One or two visits each month were made between March to September (inclusive) during suitable weather conditions i.e. settled, not too windy, dry with at least intermittent sunshine – which wasn’t always easy with the wettest Summer on record following the sunniest, hottest recorded April. This extreme weather certainly had an impact on invertebrate numbers, particularly the prolonged wet periods 4 HACKNEY MARSHES: SURVEY OF HABITATS VIEW ENLARGED MAP 5 METHODS This invertebrate survey used four methods for detecting the species using the survey area: 1 Direct observation – particularly for conspicuous mobile insects such as butterflies, dragonflies and bumble bees. 2 Turning over dead wood and other debris – revealing taxa such as woodlice and molluscs as well as certain spiders and beetles. 3 Beating Tray – this was used for systematically beating the foliage of shrubs, lower branches of trees, and stout herbaceous plants. 4 Sweep Net – for sweeping invertebrate denizens of grass/herb communities. The following taxa were identified and recorded – all species of the following groups: Odonata, Orthoptera, butterflies and macro-moths (as well as a few distinctive micro- moths), shieldbugs and their allies, Coccinellidae, social Hymenoptera and Isopoda, as well as a good range (but not exhaustive) of Coleoptera, Syrphidae, spiders, molluscs, and a few distinctive species of other groups. The survey was conducted by dividing the site into six agreed habitat areas, which are coded from numbers 1 to 6 in the invertebrate list below; the presence in each zone is indicated by a + symbol. The six zones are as follows: 1 A linear walk of over 1 km along the Old River Lea, from the bridge across to East Marsh north to Friends’ Bridge, bordered by the water to the East and a tarmac path to the West. Early in the season, the river-edge mud was much exposed; but as the season progressed, it was swamped by the vigorous, alien annual Himalayan Balsam, Impatiens glandulifera, which then formed a near monoculture. An attractive if not particularly welcome plant – few if any invertebrates seemed to feed on its leaves, although the nectar-rich flowers were relished by some bees. Another dominant alien along the river, in slightly drier areas, is the Russian Comfrey, Symphytum x uplandicum, which is similarly used by invertebrates primarily as a nectar source. The walk is principally through secondary woodland, in which poplar, Populus, and willow, Salix, species are dominant, although a wide variety of other native and exotic trees are also present. Shrubs include Elder, Sambucus nigra and some Prunus species. The ground flora isn’t particularly diverse and indicates a nutrient-rich soil. In the Spring, the area looks attractive with the massed umbels of Cow Parsley, Anthriscus sylvestris. Though not the most productive of plants for insects, it supported populations of two Notable species of beetle – the longhorn beetle, Phyoecia cylindrica (one of two species of longhorn beetle in the UK that use non-woody plants); and the leaf beetle, Chrysolina oricalcia. Nettles, Urtica dioica, are a dominant part of the field layer and support a wide range of fauna, including: snails; larvae of vanessid butterflies and various moths, such as Mother of Pearl and Angle Shades; aphids, which support aphidophagous insects, such as some hoverfly larvae and ladybirds; weevils, such as Phyllobius pomaceus; various bugs, such as Heterotoma planicornis and Calocoris stysi; not to mention a hunting ground for spiders. The Nursery Web Spider, Pisaura mirabilis, was seen in some numbers basking on these ubiquitous plants. 6 Other widespread herbs included: Goosegrass [or Common Cleavers], Galium aparine; Burdock, Arctium minus; and Hogweed, Heracleum sphondylium. Dead wood piles are another useful micro-habitat in this zone, providing shelter and/or food for animals as diverse as woodlice, earthworms, molluscs and spiders. The biggest surprise turning over some wood in the wettest areas were numbers of the introduced Australian amphipod, Arcitalitrus dorrenei, which is the only UK terrestrial species. Known mainly in parts of south-west England, it has been recorded in the London area in places such as Kew Gardens. 2 This zone runs parallel to Zone 1 to the West of the tarmac path. The habitat is similar to the drier parts of Zone 1, though with a slightly more diverse flora, and incorporates the areas known as North and East Woods. To the inside of this zone are some small mini-meadows with saplings, which hold various grassland species otherwise absent from this zone, such as Roesel’s Bush-cricket, Metrioptera roeselii, and Bishop’s Mitre, Aelia acuminata. Survey Zone 2. Click on the photo to enlarge it. A range of shrubs can be found growing here, including: Spindle, Euonymus europaeus; Gorse, Ulex europaeus; Holly, Ilex aquifolium; and Apple, Malus, species. A variety of herbs were flowering in sunny edges, including: White Dead-nettle, Lamium album; Black Horehound, Ballota nigra; Cut-leaved Cranesbill, Geranium dissectum; and Common Mallow, Malva sylvestris. The woodlands of Zones 1 and 2 provide breeding habitat for a range of breeding birds, such as Sparrowhawk, Stock Dove, Green and Great-spotted Woodpecker, three species of tit, and Blackcap. 3 Meadow – this area is situated at the northern end of the site, between Friends’ and Cow Bridges, and with electricity pylons within the area fenced off for security. This contains a mix of meadow grasses, such as: Cocksfoot, Dactylis glomerata; bents, Agrostis spp.; and less- welcome False Oat Grass, Arrhenatherum elatius. A wide selection of forbs [non-woody plants other than grasses, sedges and rushes] include: Black Knapweed, Centaurea nigra; Ox-eye Daisy, Leucanthemum vulgare; Wild Carrot, Daucus carota; Salad Burnet, Sanguisorba minor; Field Scabious, Knautia arvensis; and Bird’s-foot Trefoil, Lotus corniculatus. Given its sheltered and sunny position, this is one of the richest areas for insect life, with a good mix of grasshoppers, bush-crickets, mirid bugs, flower-visiting butterflies, hoverflies and bees. A few ant-hills are present, which are also appreciated by the local Green Woodpeckers. The meadow is managed by an annual mow. 4 Scrub belt behind meadow (Zone 3), comprising a variety of native shrubs including: Hawthorn, Crataegus