Bio-blitzing Perch Pond – 5 October 2014




As of 22nd October, the species list for the 5th October bio-blitz in Wanstead Park stands at 148, excluding plants and lichens. Probably the most popular activity on the day was the pond-dipping, organised by Derek McEwan. Derek almost had to be dragged away from the east end of Perch Pond, where he set up base, such was his enthusiasm for discovering what was in the waters of that lake. Derek’s species summary makes fascinating reading. Summarising, he found:

  • 3 species of freshwater leech (subclass Hirudinea).
  • 1 species of horsehair worm (phylum Nematomorpha).
  • 12 species of molluscs, including a variety of freshwater snails and mussels.
  • 2 species of crustaceans, the most dramatic of which was a large American Signal Crayfish.
  • 1 species of true fly (order Diptera).
  • 9 species of water bugs, the most common being Greater Water-Boatman, and with four species of Lesser Water-Boatman.
  • 6 species of water beetle, including the fascinating Screech Beetle (Hygrobia hermanni), which let out an audible squeak when touched.
  • 6 dragonfly and damselfly species, including the larvae of Common Blue Damselfly and Red-eyed Damselfly; there was also a very late flying Black-tailed Skimmer.
  • 2 fish species, Perch and Roach.

Derek commented: “It’s always dangerous to make assumptions based on just one set of data, but there are some interesting general  trends. There seems to be a very good variety of freshwater molluscs in the Perch Pond, especially water snails and bivalves. Crustaceans, including shrimps, water slaters and Signal Crayfish, are also plentiful. On the other hand there were no caddis, alder or may-fly larvae, and very few Odonata larvae – even in the littoral zone at the margins of the pond. This is despite the pond-dipping always being attended by several flying adults e.g. Migrant Hawkers and Common Darters. There were also very few predatory water beetles with just one specimen of Acilius sulcatus and no Dysticus or Agabus species. I’m not sure if it’s because of the late time of year, or if the numbers of predatory fish are having an impact and the larger, more conspicuous beetles are not having the chance to reach maturity. It’s also possible that the algal blooms may be having an impact, but there’s enough clear surface water that I think it’s a little unlikely. The scarcity of Lesser Water-Boatmen (Family Corixidae) was also surprising, with just a few individuals found during the day. Although well-represented, there were also fewer Greater Water-Boatmen (Notonecta glauca) than I had expected and just a single Hesperocorixid and Water Scorpion (Nepa cineria). Again, I would have expected to find more in a lake of this size/water depth. Further studies should help – it would be especially interesting to compare the Perch Pond with the other lakes in the Park like the Shoulder of Mutton Pond, to see how water quality/invertebrate life varies across the site.”

The Wren Group is preparing plans to do more bio-blitzes in 2015. Watch this space!


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October 23rd, 2014

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Bio-blitzing the Park – 5 October 2014

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The day dawned frosty, but with hardly a cloud in the sky by 10am it was warm and sunny as people assembled in Wanstead Park for the Wren Group’s first bio-blitz. The Lakehouse moth-trap had already delivered nine species of moths, and the efforts of Bob, Dan, Debbie and Tim had produced a good selection of birds on Wanstead Flats, including a party of Skylarks that had deserted their breeding area and returned to their winter feeding quarters – on the other side of Centre Road! Other birds found on the Flats during the day included a Stonechat and Linnets, but there was no visible migration of note.

Back at The Temple, after a showing of four of the moth highlights – Black Rustic, Shuttle-shaped Dart, Pink-barred Sallow and Lunar Underwing – Derek took charge of the pond-dipping session in Perch Pond, while Gill, Cathy and Jackie led a group listing invertebrates, plants, lichens and fungi in Chalet Wood. David scoured the Park for birds, while Rose went off in search of anything of she could find. A large Signal Crayfish and several Perch ended up in pond-dippers’ nets and four species of dragonflies were seen over and around Perch and Heronry, including a very late Black-tailed Skimmer. Good numbers of Red Admiral butterflies, along with a few Large Whites and Speckled Woods – and a lovely, fresh Small Copper – were on the wing over The Plain. Cathy picked up a Buzzard soaring over The Glade and a few minutes later it drifted south over The Plain. Unusually these days, both Treecreeper and Nuthatch were recorded: Cathy heard the latter calling in Chalet Wood, while Dan saw a Treecreeper in Bush Wood.

A selection of interesting aquatic invertebrates was showcased at The Temple. These included an extraordinary squeaking water beetle, probably Acilius sulcatus, and a Great Water Boatman, Notonecta glauca. As the afternoon wore on, people were still trying to add new species but we called it a day at 3pm. With various people working on the identities of mystery bugs and lichens, we hope to have a comprehensive list in a few days’ time. My hunch is that we’ll top 150 species for the day.

Thanks to the City of London for letting us have use of a room at The Temple, and thanks to the 30 people who took part, particularly Cathy and Derek, who travelled all the way from Reading. Judging by the positive feedback, there will be more bio-blitzes to come!

Tim Harris


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October 6th, 2014

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Join our Bio-blitz on 5th October!

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Sunday 5th October
10:00 outside the tea hut in Wanstead Park (100 metres north of the Northumberland Avenue entrance)

On Sunday 5th October we will be conducting a bio-blitz in Wanstead Park. This is a fun activity, but with a serious aim, as we try to find as many species as we can – birds, insects, spiders, plants and anything else we can come across. Identification guides will be at hand and anything we get really stuck on we’ll photograph for later identification.

We hope to have a team searching in the leaf litter in Chalet Wood, another group identifying invertebrates on The Plain, and other people counting water birds on the Park’s lakes. If we have enough people we might also have a team working in the Old Sewage Works. Simultaneously, a group of birders will be logging visible migration on Wanstead Flats.

If the weather is fine the previous night a moth-trap will be run locally, and interesting moth species will be shown in The Temple. If the weather is poor we may have to change our plans.

To help us plan for the event, could anyone wishing to participate please contact Tim Harris (email: or phone/text 07505 482328).


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September 22nd, 2014

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