Danson: lack of algal mats hits Red Eyes

There was an almost complete lack of floating algal mats at Danson lake on 29th June. I had gone to check on Himalayan Balsam eradication efforts, but also to see if both  species of Red Eyed Damselfly were now on the wing. These sit in numbers on the algae. Either the Council has been very efficient at removal, or environmental conditions have reduced it, or a combination of both, and there was little sign of Hornwort reaching the surface. The result was that only 1 adult (Large) Red Eye was seen, and that was reduced to defending a territory from a discarded orange plastic bucket lying near the lake margin, from which it was seeing off mobile Common Blue Damselflies, but tolerating five newly-emerged adults that had hauled out and could not yet fly.

If the Council has had a hand in this, it’s another example of how the simplistic ‘blitz it all at once’ approach to vegetation management doesn’t usually give the best results for biodiversity.

Azure, Common Blue and Blue-tailed Damselflies were on the wing in strong numbers. 4 or 5 different male Black-tailed Skimmer Dragonflies were seen, in some cases clashing over territory.

The south side of the lake is a good place to see Large Skipper butterflies, and 5 or 6 were noted. Several Meadow Browns were amongst long grass. There were 3 Red Admirals in the ‘woodland ride’ along the tarmac track leading to the gate in the south-east corner of the park, and my first Purple Hairstreak of the year.

All 5 Mute Swan  cygnets have survived so far. There were 44 adult Canada Geese and 6 young. 5 Swifts were over the lake.

No Himalayan Balsam seedlings were found, so the eradication of this alien species may have been achieved, though further checks will be made this year and next spring just to be totally sure.

Chris Rose


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1 Response to Danson: lack of algal mats hits Red Eyes

  1. Jo says:

    Hi Chris,

    Wouldn’t it be the case that the Council need to remove weed in order to keep the rowing boats operational? In previous years, it has been almost impossible to row due to thick ribbons of weed strangling the oars. Any approach you would advocate would need to take account of the designated purpose of the lake which is to act as a watersport facility in the borough.

    I don’t know if the algal mats of which you speak are something other than the weed, but it seems likely that to remove one would have an impact on the other. I too derive enormous satisfaction from observing the range of wildlife taking its rightful place on the lake, aided by a good deal of sensitive protection from the watersports team. I think we need to consider the aims and objectives of maintaining the Danson lake, and come up with a constructive solution which the watersports team will be able to realistically adhere to.

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