Monday, 30 November 2009

A Back Entrance

While driving round the edge of the field that lies next to the Burnieshed burn, I noticed this hole. It is the landward entrance to a burrow, whose underwater entrance is somewhere in the bank of the stream.

At night the beavers come out of their burrow…

They walk into the field along the paths that they have made and, at a certain point, stop to graze on the stubble turnips that were planted late in June to provide lambs with fodder on which to fatten before going for slaughter in December.

If you look carefully you can make out the branching of the paths.

From the point of view of a farmer the grazing of the stubble turnips is not very significant, but danger lies with the burrow that underlies the big hole that we saw in the earlier photos on this post. In spring a tractor, ploughing this field could fall into the burrow and be damaged expensively.

What is the answer?

Fill the hole with stones and so evict the beavers from their home?

Trap the beavers and translocate them?

Widen the riparian fringe to take into account the likely distance that beavers would burrow?

Thursday, 26 November 2009

The Wet Wood - Changes and the Canal

Some visitors came from Aigas yesterday (Wednesday, 25th November). The rain rained and the wind blew. We walked along the Burnieshed Path (aka Cateran Trail) and looked at the dams and pools.

After lunch we went over to the Wet Wood. I had not been there for about a fortnight and was very much impressed with some of the changes.

This photograph shows the greatly worked on dam, whose tiny beginning you see in the next picture but one. The leaning fence straining post just to the left of the dam can be seen in the next two photographs.

The straining post of an old fence can be made out about the middle of this photograph. To the left of the dam you can see a fallen ash tree (pre-beaver) on which an otter had left many spraints earlier in the year. You can see this tree trunk in the next photo.

The dam has been greatly built up with the stems of Sweet Reed Grass (Glyceria maxima).

The combination of the heavy rains and the building up of the dams has raised the water level of this pond and the low ground near it a great deal, as the later photographs show.

This photograph, taken in the early summer of 2003 shows the dam, illustrated above, earlier in its history. The fallen tree trunk is on the left of the picture.

The straining post is in the top right of the picture and is surrounded by vegetation. It is covered by water up to the same level as the vegetation.

I think this photo was taken sometime in April 2004. The dam is bigger. You can see the tree trunk (it looks more like an oak than an ash) and, middle right that fence straining post, unsurrounded by the luxuriant growth of water cress (Rorippa nasturtium-aquaticum).

We walked along behind the dam and then along the side of the ditch that runs north, until it was time to cross. I chose to cross here, where the beavers have built a curious pool with a spout at the downstream end. The structure is like a funnel. There has never been any question of this being a dam.

We walked on into the groves of willow. The canal has now been extended right through one of these and meets the overflow from the little pond to the westish (West-North-West) of the larger one. The canal is quite deeply dug lower downstream and there is a small dam, as shown here.

I nearly forgot to say that I took the photographs this morning.

Saturday, 21 November 2009

Dippers and Dams

I took these photographs on Friday morning after the heavy rainfall of Thursday night that had caused so much flooding down in Cumbria.

We had a couple of inches (50-75mm) that night and the same again fell in the last 24hours until this morning (10:00hrs.), November 22nd.

The dams are holding up well so far.

The water is pouring over the tops and along the overflow passages. Some is coming through the dams as well, though not a lot.

This shot, taken rather closer to the top dam below the drive, shows you what I mean.

This and the next photograph were taken by Derek Todd, who is the webmaster of the 'Alyth Voice' and a colleague on the newsletter's editorial committee.

Derek took these photographs of the predecessor to the top dam downstream of the drive just a few days (late November 2007) before it was breached during a weekend of heavy rain.

This dam and the smaller one below were built during the summer of 2007.

As you see, the main dam crossed the burn and then had a couple of extensions that ran at an angle downstream from it. You see this very clearly in the next photo.

Here you see the dam from the path that runs parallel with the ditch.

A sycamore tree provides a pillar from which the southern arm of the dam pivots.

Downstream of the big dam there was a smaller dam.

On the night of the 30th November 2007 a flood that resulted from heavy rainfall burst the dam and the central section was washed away entirely, as was the small dam lower downstream.

By the 3rd December 2007, when I took this and the next photographs, however, the beavers had already begun to rebuild a dam a little downstream from their earlier construction.

The beavers built this new dam in line with the straining post of the fence that had bordered the ditch - you may have noticed it in photographs of the dam as it is now. The whole structure is a couple of metres east of the big sycamore that served as a turning post for the earlier dam. It has been ringed by the beavers since and has become Coarse Woody Standing Timber.

This photo is taken from the south bank of the third dam downstream from the top one.

The water is flowing straight past the dam, enhancing the new braided pattern that the stream is developing.

Back up stream - this is the middle dam - an elegant, slender structure. The overflow is at the southern end and you can see the water flowing from the left to the right of the picture.

My great delight on Friday morning was to see three dippers (Cinclus cinclus) flying about the burn and ponds.

I had not seen dippers here for a long time, perhaps years, so the return of these attractive birds is very exciting.

Dippers are characteristic of fast flowing rivers and I nearly always see them when I am canoeing along the Tay. It will be fascinating to see if the beaver changed stream will prove attractive enough for them to want to breed here, or if they will just be visitors for the winter.

Sunday, 15 November 2009

Sturm und Drang

On my way back from Forfar yesterday, I stopped at the Bridge over the River Isla at Airlie. It was in full spate and made a magnificent sight. Unfortunately, I had only my little compact digital camera with me.

Earlier I had walked along the burn after feeding the wild boar.

This birch tree came down on Friday night. Throughout the summer it supported the trunk of a sycamore that had been cut, but had snagged on it.

It had worried me that, with the sycamore resting against the top of the birch, it might fall in an unexpected way and kill the beaver that cut it. However, in the absence of a dead beaver, it seems likely that all went well

There is that felled tree again. It is lying behind the partly stripped trunk of another felled birch. To the right of the newly cut birch is the remaining trunk of the sycamore, whose other stem beavers cut last Spring.

I read somewhere that trees cut by beavers seldom snag on other trees. I must have misread this statement: in any case this is not my experience here.

Friday, 13 November 2009

The Second Lowest Dam (as it is now)

Here is the lowest dam on the Burnieshed about a year ago.

And here it is now. The beavers have added some branches as buttresses.

Upstream from the south side of the ditch where the beavers are extending the pond and swamp.

A close up of one of the cut birch trees. The skilled naturalist can tell if the trees have been gnawed by adult or young beavers from the size of the tooth marks. This can be deceptive because the width of the mark depends on the angle at which the beaver has bitten.

And a heap of chips at the foot of one of the trees.

Our ancestors in the mesolithic and since found these chips very useful as kindling with which to light fires.

It seems, too, that wood chips have their own characteristic fungi.

Saturday, 7 November 2009

Nothing Much Doing

One morning recently, I came across the Morgans. They were out for a walk with their little dog, Mo. After calling off little Mo, who had presented herself to me in a most affectionate way, and explaining that she was in season, Morgan told me that my blog lacked zing. He liked it when I was in ranting mode, but felt that photographs of rushing water and autumnal landscapes were not sufficiently exciting.

What could I say? For the moment nothing very exciting is happening. The flood waters are receding. This photograph shows the Isla at Isla Bridge, just before the confluence with the River Tay, a place where I have landed after a canoeing journey a number of times in the past. I like to go there from time to time to consider the water level, particularly after a flood. When I took the photograph the waters were still fairly high.

According to Hamish Moir, who works at the Macalulay Land Use Research Institute in Aberdeen, the Isla has a particularly rapid rise and fall in time of flood.

Having said that nothing is happening that is to ignore the fact that the beavers are very occupied with their preparations for winter.

Besides, although things seem quiet to me, there is an outside world.

Has Roger Wheater set up his committee to consider the impacts that beaver might have on salmon in Scotland? It seems that the salmon people are particularly twitchy at the moment because this past fishing season has been notably poor.

How is the Trial Release of beavers going in Knapdale?

Is it true that Allan Bantick of the Scottish Wildlife Trust has called for the release of lynx into the wild?

I must find out about these things

Sunday, 1 November 2009

A Deep Depression and Much Rain

This is a view from our bedroom window on the misty morning of the 31st October 2009.

And the top dam below the drive later that morning.

Last night, however, the forecast depression came in and rainfall has fallen heavily for the last twenty-four hours or so.

Here is that top dam again in the midst of all this rain.

This is the middle of the three main dams below the drive at Bamff, taken this afternoon at about 15:30.

And here is the lowest of the three big dams. A new one is being built about twenty five metres downstream of this one and it looks as though another one is in a very early stage of construction another twenty or so metres below that.

Why would a salmon or sea trout not manage to leap this dam?

This is a view from further downstream of the same dam. A sheet of water is flowing into the original ditch.