Thursday, March 29, 2007

Blackcaps and stuff

Nothing for a while, weather, family stuff, and an exploding tripod, and nothing for a while more as we head off to a birdless Greek Island to paddle in freezing seas and enjoy the site of an island closing down for Easter.

Wintering Blackcaps. I’ve seen a male occasionally during the winter, and a female once. This is the third year in a row they’ve been around. I’ve had the impression that the male spends most of its time somewhere in our small road as I’ve frequently heard it chirping to itself from the bottom of a bush in a neighbouring garden. So presumably the one I saw last winter over by the cricket club was a different one.

It seems to me that many birdwatchers have a resident Blackcap in their garden. So just how many are there? Say that there is one for every 30 houses – 1 per 100 people, so that’s 500,000. And say only a quarter of total habitation is suitable so that’s 125,000. And they are quite widespread.

Now for the surveys. According to one in Worcester . the BTO 1978/1979 survey found a total of 1714 of which Worcester had 39. A more recent survey found in Worcester found 245 males and 115 females – almost a 10 fold increase, which if replicated in the national survey would give 17,000. I think I saw a BTO survey which gave the figure of 10,000.

So there’s a ten-fold difference between my crass estimate and the survey. I know mines a rough guess, but how many are there actually here in Sawbridgeworth, a town of c11,000 for instance? If there were 10 – quite likely , that would be 1 per 1000 – a population of 50,000 across the country.

The generally accepted version is that this is a German/Eastern European population that has developed a separate migration route. But how has this happened? One theory is that this is a genetic mutation that has become propagated by virtue of its success (as the climate warms, and gardens more hospitable), and a whole new population has arisen.

Theories are easy, but evidence is difficult. Fortunately the ever excellent P. Berthold has got some – the offspring of British-wintering Blackcaps naturally orient themselves WNW in autumn, whereas offspring of Southern German Blackcaps naturally orient SW.

So presumably Yellow-Browed Warblers, Pallas’s and Dusky Warbler’s are doing the same in their wintering populations in the UK.

Sunday, March 18, 2007

Radipole - family visit

Saturday was glorious. We got down to Weymouth at mid-day, and after some beach/cafĂ©/shop things finally got round Radipole at 4pmish. We didn’t get to the North Hide with its Marsh Harrier, but we did see a Chiffchaff, a Cetti’s Warbler, and a few if the usual suspects on the water. We saw what looked like a Roach. Well we saw most of it anyway.

I’m really enjoying the new camera and 100mm - 400mm IS lens. I’m still learning on the contrast and focussing stuff, but I’m amazed at how easy getting good-ish pictures is. Also, I find I’m looking for the picture, so I tend to be getting better views of birds than if I was just ticking them off the list and moving on. Here are a few samples.







By the time we finished the loop little legs had got tired and needed picking up, so I gave the camera to D#1 to look after, with the inevitable result below.


Sunday, March 11, 2007

First Butterflies.



A Peacock disturbed from the garage, then a trip to Hatfield Forest with senior Dipperette and a fluorescent Brimstone, then home and another Brimstone.




Hatfield Forest was more of the same from yesterday. Jackdaws, Wood Pigeons, and not much else. On the lake numbers down considerably, but a pair of Shelduck looking glorious in the sunshine, and somewhere a few Chiffchaff notes broke the cackling of Jackdaws. Where have all the peckers gone?


And back home the Blackap was singing. More on wintering Blackcaps later

Saturday, March 10, 2007

All the birds are dead or have flown.

One subject that seems to me to be significant but uncommented is the fluctuation of bird populations during the year. If we start off with a pair of birds in March, and they raise on average say 5 young during the year then come September there are 7 birds – 3.5x the starting population. By the time we get back to March we are back to 2. That seems to me to be one reason why November is often a good month and February is a dull one – there are less than half the number of birds around in February there were in November.

Well that’s my excuse for seeing nothing down the Marsh this morning. A good number of Wrens, 2 Jays, a Reed Bunting, A Goldfinch, a Greenfinch, some long-tailed tits, and a Water Rail calling. Apart from that and a few odds and sods just nothing.

Here’s my first bird picture with the new Canon 100mm-400mm IS lens.


It’s great. Just get the subject in the centre of the viewfinder, half press to get it in focus, then click and it’s in the memory banks. That’s my kind of photography.

Sunday, March 04, 2007

Lunar Eclipse

It was too good an opportunity to miss, so I set up the Kowa TSN-821 32x wide angle, got the Samsung i-5 ready, realised I couldn't find the Contraption, so held it to the eyepiece and fired away.
When the moon was in full eclipse the exposure was 1s, so the results are a bit blurred. I was going to put them up here but then i saw Bogbumper's pictures here and realised there was no point as hers are just so much better. so here's a picture of a Portland Screw (I think) instead. Its the interior of the original shell.

Friday, March 02, 2007

Cranes!!

Not Grus grus, but the construction sort.

Some time ago I read/saw or otherwise absorbed that sky scrapers are hung from the top not supported at the bottom. The logic is that if the outer walls are structural then in the event of a tremor or strong wind the whole structure will shear and cause damage, whereas if it is suspended from a strong central column then it will bend and retain its structure.

I took the opportunity of looking at a couple of skyscraper pulli going up at the east end of Canary Wharf to see if I could spot this. The first is just the lift shaft going up. It looks an immense block of concrete, and already has the floor numbers on.


The second is more developed, and the floor construction seems to be sprouting out of the central lift shaft.



If anyone has more knowledge or has spotted mistakes then please let me know!