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Disrupting garden pond ecosystems

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Old Saturday 13th September 2003, 16:07   #1
Richard
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Disrupting garden pond ecosystems

Are there any garden pond experts out there? Does anyone know of a good information source for garden ponds and wildlife?

Earlier I decided it was time I made an effort to remove some of the rotting vegetation on the bottom of my pond. It only has a maximum depth of about 12 inches so I had decided to use my hands to clear small sections every few days. This way I need only disturb the sediment in a small part of the pond at any one time.

Today, with only a few handfuls of mud etc I found 3 hawker larvae and I wonder how many I missed and thus 'killed'.

Is there a best time of the year clear the sediment? If I waited until the colder weather the larva will still be there and, I presume, will be hibernating and inactive so harder to see. Perhaps I should leave the ecosystem well alone as, thanks to the snails, the water is clear .

Thoughts or advice anyone please?

Richard
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Old Saturday 13th September 2003, 17:28   #2
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Richard,
I recently bought (via Amazon) The Wildlife Pond Handbook by Louise Bardsley published for the Wildlife Trusts by New Holland. It is subtitled "A practical guide to creating and maintaining your own wetland for wildlife". The book looks excellent.

The advice on maintenance is basically to do it between autumn and Dec. when most pond species (in the northern hemisphere!) will be inactive. Rescue as many things from the silt as possible. Retain some silt or they won't have any habitiat left. (This is just a potted summary.)

My wife and I built a pond about 18 months ago but we are moving house soon and want something bigger and better next time.
For reasons I won't bore you with, we had to drain our current pond... we were amazed how many dragonfly larvae and small fishes were in the pond. Fortunately a neighbour gave them a new home.
Good luck
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Old Sunday 14th September 2003, 08:26   #3
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Thank you for that advice Ken. I will have a look on Amazon

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Old Sunday 14th September 2003, 10:52   #4
Nina P
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Richard, I will be doing my pond, hopefully today, when a friend who helps me with the difficult jobs will be here, there are a few tips I can offer you...
1/ what you lift out put on a plastic sheet, close to the pond.
2/ Whilst lifting material try to put what is alive into a bucket, with some of the pond's water.
3/ Do what you intend to do as quickly as possible.
4/ before replacing anything, try to get a deep place, 1ft 6ins deep min, as this is the survival area for pond life during winter.
5/ what you are not replacing, leave as close as you can to the pond for at least a night, so that anything hiding in there can return to the pond.
Does that give you enough information? Nina.
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Old Sunday 14th September 2003, 15:37   #5
Richard
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Thanks for that reassuring advice. I read this and decided to 'brave it' and cleared some more out today. I found upwards of thirty larvae by spreading out the mug and debris. They all looked the same species but several were larger than the others so maybe not Migrant but Southern Hawker. I have a key which should distinguish them but it is difficult to follow. I took some pics and wonder if there are any pictures of larvae on the web for comparison - will have to go and look.

One other question, which I suppose is common sense, relates to adding fresh tap water. I guess this should be avoided but as the pond is about 8'x6' would adding a gallon or so over very few days upset the wildlife? Perhaps I should let it stand for a day or two first.

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Old Sunday 14th September 2003, 15:43   #6
Michael Frankis
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Quote:
Originally posted by Richard
They all looked the same species but several were larger than the others so maybe not Migrant but Southern Hawker.
Or perhaps just different ages - dragonfly larvae are in the water for up to 5 years before they hatch out as adults.

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Old Sunday 14th September 2003, 17:59   #7
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We always put water into a couple of water butts and allow the chlorine to evaporate before putting it in the pond...
but I'm not an expert.
On the larvae question, I've attached a pic of a presumed southern hawker larva -- I've never seen a migrant hawker laying eggs there. Common darters look completely different.
Of course, it's impossible to be certain that an emperor or a broad bodied chaser hasn't laid some eggs when I wasn't looking.
As Michael says, the larvae go through quite a few 'instars' (stages) by a sort of progressive moult, so just being different sizes doesn't mean they are different species. By the time they are near to emerging, you can see the wing cases.
Brooks' book has a good key of late instar larvae.
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Old Monday 15th September 2003, 07:47   #8
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Thanks Ken,

Yes - Southern Hawker. I was about to upload a pic but it looks the same as yours!

I am bookless at the moment having lost Dan Powell's book (which didn't show larvae anyway) and having ordered Cyril Hammond's book over six week ago from Amazon - they are having trouble getting it. Someone (maybe you) has mentioned the Brooks book before. Is it called "Dragonflies" and published by The Natural History Museum? Is it reasonably good?

Richard

PS I have already orderd the Pondlife one you suggested.
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Old Monday 15th September 2003, 08:00   #9
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Field Guide to the Dragonflies and Damselflies of Great Britain and Ireland by Steve Brooks. Price is 18.95.

On Amazon it says, "This hard-to-find title is subject to an additional handling charge of 1.99 per item."

I bought mine from Old Moor RSPB reserve in South Yorkshire. Apparently they get sold out fairly quickly, so I'm not sure how many other places will have them in stock.

You could try Subbuteo Books - http://www.wildlifebooks.co.uk.
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Old Monday 15th September 2003, 09:06   #10
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Richard,
Make sure you buy the right one! Steve Brooks is a dragonfly expert at the British NH Museum and has written various books. The field guide, as outlined by Digibirder, is the one you want.
If poss. get the 3rd edition which has a couple of new (to the UK) species in.
You may be able to order it through the British Dragonfly Society web site.
Otherwise I've had good service from Books for Birders (which I seem to remember don't charge for P & P unlike Amazon who just whacked me for 4.95 postage on the new moths book )
Good luck
Ken

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Old Monday 15th September 2003, 10:58   #11
Richard
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Quote:
Originally posted by Surreybirder
Richard,
Otherwise I've had good service from Books for Birders (which I seem to remember don't charge for P & P unlike Amazon who just whacked me for 4.95 postage on the new moths book )
Ken
Thanks to both of you.

Ken you are right about 'Books for Birders'! I've just ordered from them - no postage charge!! I will use them again!

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Old Monday 15th September 2003, 20:21   #12
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Hello again Richard, I got my pond done yesterday and was pleased to note that I had 15 frogs in there as well as several dragonfly larvae, just like Surreybirders picture too. I had to top up the pond too, but I did use tapwater to do this, but rainwater or butt water are prefferable. My pond is now well cleared, and I have found all my water plants, which were lost in the reeds, and hopefully the water will smell sweeter as it was becoming putrified, hence the need to get it done!! Good luck with your work, and I do hope it look good afterwards. Nina.
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