Tuesday, June 21, 2016

Climate change: Global Warming Posts

Global Warming is a critical subject of our times. The debate has been raging for a few decades now, and there is still considerable disagreement and scepticism. There is a particular relevance  for those interested in the natural world as environmental changes clearly have the capacity to cause havoc, and bird watchers of a particular vintage have seen significant changes of the bird population in our life time. So with some time on my hands I decided to investigate.

I am sceptical by nature. US politicians pronouncing there is no global warming and there is a giant conspiracy are scary sure enough, but I’m not sure I like the incessant hectoring about imminent catastrophe by various groups all of whom seem to have some vested interest in creating scare stories about the climate. In addition there is significant disagreement about basic scientific questions.  So, who to believe? Who to trust?

I have a background in science, but not any particular knowledge of climate science, so much of this is new to me. There are thousands of scientists working on a variety of different aspects of measurement and explanation of climate science, so trying to give an overview that does justice to the sheer quantity and depth of work done is in many ways an impossible task. I have been down a particular avenue of inquiry and ended up with a particular set of conclusions, but that is just my view; someone else could engage in the same exercise, take a different route, and end up with different conclusions.

I’ve split the investigation into four parts:

i)               Is the world warming? (answer – it is)
ii)             Is the warming caused by man’s activities?
iii)            Is something very bad about to happen?
iv)            What are the effects (current and future) on wildlife?

I’m still researching and writing the posts so they will appear sporadically amongst the general rubbish. I’ll tag the posts so you can pull them all out in one go.

Wednesday, June 15, 2016

Grumpy man birding

In grumpy mode today. Titchwell or the Brecks? Titchwell has had a good run but surely there's nothing there in the middle of June, and the Brecks are bursting with really easy ticks, so the Brecks it is. First up King's Wood. The place with the highest concentration of Woodlarks in East Anglia. Well not when I'm there. Then as I'm leaving an old chap engages me in conversation, and yes its a pleasure to talk to him, but there are ticks to be had.

On to Mickle Mere for the Glossy Ibis. After getting lost down myriad tiny roads I find it, and its a gem of a reserve, a shallow mere in Breckland with lots of waterfowl - Shoveler, Shelduck, Teal, Redshank, Oystercatcher, Little Egret. Just one bird missing. A local pops up to tell us what a marvellous reserve it is, smashing views of Cuckoos etc and the Glossy Ibis will be along soon, which it isn't. We are swapping tails and anecdotes and I am just about to deliver the side-splitting punch-line when the local says - "its just there behind you" and I think well that's a bit rude interrupting my tale, and that isn't the punchline anyway, when I realise he is referring to the Ibis, and as I turn round I get a nano-second of black something going into a willow. He is sure that was it, and I am confident of two things; he is right, and it isn't coming out of there any time soon.

So desperation mounting and on to Weeting Heath. Surely, surely, this time a year tick. The Stone Curlew chicks have apparently just been eaten by a fox, but there is a walk through the woods opposite with lots of great heathland birds including the recently bereaved Stone Curlews. Head down and off I go, meeting a couple of genial old birders who inform me I have walked past the birds. I retrace my steps, set up scope, and there are a couple of Stone Curlew, some way apart, sitting morosely looking for all the world like two birds who have flown a couple of thousand miles for the sole purpose of breeding and just watched their children being eaten. If I have ever seen two more miserable looking birds then I cannot remember it. Onwards to the top of the forest and a watchpoint "Tree Pipit, woodlark, can't miss 'em". The words of doom. I get there and sure enough there is nothing. Hang on, some Curlew, and something singing from a tree. It is probably the Pipit but I have no audio media with me and I have to wait to get home to discover that yes, it probably was, but it doesn't show and certainly doesn't do a parachute-song-flight thing, so it avoids being added to the year list.

And then something unexpected. Subsequently I find this is quite a good record for the site; its a male Marsh Harrier. And yes its nice to see but there are flocks of these things not far away.

Finally I get lost coming back to the path and end up being dumped out on a flat straight A road for the walk back to the car with drivers hurtling past at speed. Oh well. I'm sure there was nothing at Titchwell. Oh hang on, there was this.

Monday, June 13, 2016

Badbury Rings

Final stop, Badbury rings, an ancient hill fort. Now preserved for posterity by the National Trust. The rings have not been disturbed for ages, presumably since the Durotriges tribe dug them out, and is home to a variety of plants.

Common Spotted Orchid was everywhere in good numbers. Scattered amongst them, particularly on the southern sides, were Greater Butterfly Orchid. There were a few Bee Orchids showing too, a gorgeous deep pink.

Badbury rings wouldn't be famous for orchids if it were just these three orchids, and I think I found a Fragrant Orchid but it is just coming into bloom so a little early. The Frog Orchids I didn't find, but then neither did Aidan

2 Cuckoos flew past, and a Corn Bunting sang from the perimeter fence. A Small Blue and some Common Blues were amongst the butterflies seen.

I think those long spurs indicate Fragrant Orchid?

Left at 6pm with a really nice clear relaxed run up the M3 and M25 with some of the finest jazz-rock to have come out of the Netherlands in the first half of the 1970's on the player. Here's a sample.

Sunday, June 12, 2016

Paying Respects to the Naked Man

If you are interested in wildlife, and find yourself in early summer in Dorset with some hours to spare, then you really should go and pay your respects to the Naked Man.

And so to Cerne Abbas, a picture postcard village a few miles north-west of Dorchester, nestled amongst gentle rolling hills.

A typical house in Cerne Abbas.
The hills to the north west were the focus today, and in particular the south-facing slope, ancient meadows alive with butterflies. The commonest butterfly,  yes the commonest, was the fantastic Marsh Fritillary. Just everywhere, fluttering from dandelion to dandelion.

still struggling with the depth of field on the Macro Lens ...

Amongst them were other butterflies; Meadow Brown, some unidentified blues, Speckled Wood, and two skippers: the appropriately named Dingy Skipper and the spectacular Grizzled Skipper.

Dingy Skipper
Grizzled Skipper

And finally the man himself; the Cerne Abbas Giant. I was on the slope on the LHS of this picture. Common Buzzard on the right.

As a postscript, one way to ruin a day out is to immediately on your return google the place you've just been and see what others have seen here. Those Speckled Woods; they were quite well marked. Am I sure they weren't Duke of Burgundies?  Its too late now - no photographic evidence to review. Next time I will be prepared.

Friday, June 10, 2016

How far away is that bird?

bird-wise the Dorset trip finished with an atmospheric Arne reserve in the late evening on Tuesday, with several Nightjars churring away (but unfortunately not seen), and a brief but clear view of the Great-Spotted Cuckoo in flight at Portland Bill. Given the choice of spending a couple of hours hunting for the thing at a cold and windy fog-bound  Portland or heading off to find some sun I headed off. More of where I ended up in subsequent posts.

But back to that Goshawk sat in a tree. It was distant, just visible as a pale blob through the binoculars, then clearly identifiable as an accipiter with the scope turned up to 60x. But just how far away was it?

Technical data on the Kowa 883 is surprisingly difficult to find, but according to a review of the Kowa 883, the field of view at 60x is 1.1 degrees.  The bird filled about 10% of the viewer from top to bottom so that is 0.11 degrees, and the bird itself being a female is around 40 cm high.

So simple geometry is that the distance x times the angle a in radians gives the height h of the bird. Reversing that and dividing the height of the bird by the angle in radians gives the distance. So:

  •  0.11 degrees x pi/180 = 0.0024 radians. 
  • 40 cm/0.0024 = 166 metres.
So on that calculation the bird was 166 metres away. But there are quite a few sources of error on that. Firstly the FOV at 20x is 2.2 so by my simple calculations the FOV at 60x is 2.2/3 = 0.733 degrees. Perhaps the bird stands 50 cm high and it was only a 15th of the total top-to-bottom distance, so put those numbers in to the calculations and the distance becomes just over 500m. Put 1.1 degrees, 30cm and an eighth of the height and get 125m. So that's somewhere between 125 m and 500m with the middle calculation being 166m

From these calculations a rule of thumb is that at 60x and 10% of the view-finder height, a 10cm object = 50 m distance.

I don't think it was 125m away.  It was nearer the 500m, but maybe only 300?

Anyway, next time I'm in this position I'll think about the size of the image in the viewfinder and the likely size of the bird. Maybe do some tests of cars at a known distance. Something to work on ...

... and if you spot a simple mistake, please let me know in the comments section.

[updated with a correction]

Morden Bog

One of my favourite blogs is Dorset Diary by Aidan Brown. His fantastic knowledge of the natural world and top photographic skill come together in a blog that takes a corner of Dorset and turns it into an English Serengeti. So on my brief Dorset trip I went to Morden Bog mainly just to see the place from where so many great posts have come.

It was mid-afternoon mainly against the sun, and its a large area but nevertheless I saw Dartford Warbler food-carrying, Hobby, Kestrel and Buzzard  as well as more common birds such as StonechatMeadow Pipit, and Linnet. There was other wildlife with Sand Lizard and a few dragonflies.

There were a number of fat chasers over a small boggy area which proved quite hard to photograph. the best I could do is shown below, and I think from the book it is a female Four-Spotted Chaser due to the two-tone abdomen.

Whilst trying to photograph these I noticed a short strand of fine red filament drifting onto a grass stem. and here it is, I think a male Small Red Damselfly due to the red legs.

Finally, a shot of the heath to give an idea of this small piece of wilderness. Some great atmosphere in the summer heat.

Dorset trip 8-9 June

Another trip to Weymouth. First an opportunity to enjoy some traditional southern habitat on a sun-drenched Wednesday. By mid-day I was with a small group at Acres Down looking over the woods towards Bolderwood. The sky was clear, but a scan revealed a bird in a distant tree. It was clearly an Accipiter, and quite a fat one at that. Eventually it flew off and it was clearly a Goshawk, probably a female.

By that time the heat was building and Buzzards were beginning to appear in the distance. At one point we had about 4 in the air, and there was a certain amount of confusion as people would be looking at different birds. I was quite out of my depth here, and the locals clearly had much more experience. They called out some likely candidate Honey Buzzards, and when they departed a couple of hours later they were happy they had seen at least two. The key features being:

  • long tail, small slightly extended head.
  • pinched in base to the wing.
  • Flight with wings low, sometimes almost kite-like in the appearance as they glided.
  • Corkscrew display
After they had left I went further over to the more traditional watch point and chatted to a local who had been watching over the same area. They had a few Goshawks and a possible Honey buzzard but all the near ones were Common Buzzards. The second local said they don't lift their wings above the horizontal, and flap down from the elbow. The wing-clapping behind the back is diagnostic as it is only done by Honey Buzzard. Well what's a relative novice like myself to think? Perhaps I will have to visit slightly earlier in the season next year.

There were Stonechats aplenty, and in the woods Nuthatches, Coal tits and Treecreeper, but the stand-out species but far was Firecrest. From the off Firecrest song was heard all over, perhaps no surprise given that holly bushes and holly trees were everywhere. I saw 4 birds without too much difficulty, males singing in trees, but there were clearly many more. The rise in the Firecrest population is quite marked, and one I will return to in a future post.

Monday, June 06, 2016

Some things that fly that aren't birds

Some insects noted on recent trips. In no particular order

A hoverfly that caught my eye in Hatfield Forest. I believe it is a form of Volucella Bombylans that is mimicking a Red-Tailed Bee, so called Batesian Mimicry which is where things that aren't dangerous mimic things that are dangerous to discourage predators.

Ashy Mining Bee. I was out on Otley Chevin and noticed these coming, appropriately enough, out of holes in the soil. Apologies for the lack of crop on this picture but it came from my phone and as such is resistant to any form of editing.

Brown Argus ?? Very hard to distinguish from Common blue female I understand, but my best guess is Brown Argus, seen at Sawbridgeworth Marsh.

Something small and blue fluttered past. Perhaps at last I might get a photo of a Common Blue? But when I looked where it had settled - no butterfly! Instead this. I've no idea what it is.

Lots of these around at the moment. Female Banded Demoiselle, taken with the Sigma Macro. Perhaps there is hope for my photographic skills yet.

Saturday, June 04, 2016

Thames Estuary - What's that bird?

Out and about in the Thames Estuary last week - Vange, Wat Tyler, Bowers Marsh, seeing the usual kind of stuff for late may: Red Footed Falcon, Black Winged Stilt, Bearded Tit, Avocet, hobby, together with all the usual summer stuff. 

Then a bird singing from a hawthorn bush by a reedy ditch. It's a warbler, but which one? Its an unfamiliar song, kind of like a whitethroat but longer, more subdued, and with some bits and pieces in there - Linnet? I hung around for about half an hour trying to see it but it just stayed in the middle of the bushes. Something briefly flycatched, and then flew off to a more distant bush. small and brown. So, unsure, I trudged off to the Stilts.

Then a week later I'm taking some photos on my phone, and what's this? Then I remember - I'd tried to make a video of the bird song but was running out of juice, hadn't done it before etc etc. Anyway I  clicked on it, and there chuntering away is the bird. So, any thoughts as to what this is?