Thursday, 7 January 2010

New Year 2010

We have entered the New Year with all of our lakes frozen over and a powdering of light snow. Night-time temperatures are falling to less than -5 deg C and mid-day it is only about freezing point, so it is a very hard time for wildlife, especially mammals that cannot migrate away. For this reason, we have had a lot of mammal sightings this week. I have seen up to three different foxes and four deer on a single patrol. Yesterday I saw two weasels and another was reported. These animals are normally very shy and practically nocturnal, but hard times have forced them out.

The whole of the Nearctic and Palearctic regions, from Texas to Beijing, are experiencing unusually low temperatures. In the Atlantic, the Gulf Stream is weak and the high altitude Jet Stream is much further south than usual. This means that our habitual stream of mild air from the Caribbean is not reaching us and we are being subjected to high pressure continental air instead. Imagine a big, stationary lump of cold air, like a pile of porridge over Norway. As it sinks to ground level, it spreads out over the North Sea and eventually reaches the East coast of the UK. That's the simple view. Now stir the porridge slowly anti-clockwise to represent the spin induced by the rotation of the Earth, and that explains why the wind might come from the South West, but still bring snow from Norway.

For birds this is a hard time too. Seed-eating birds such as finches will still find food at this time, but dry seeds make you thirsty. Where is the water? Waders cannot probe the frozen ground and wildfowl cannot swim on frozen lakes. Many winter birds migrate South West taking them to Ireland, Spain or Portugal. A lot of continental birds might waste valuable time coming to the UK when we are already frozen. If they hang around here they may die. They have to move on, but Ireland is already freezing as well.

This week has brought a high number of bitterns to the UK. They have been seen standing around on the ice looking weak and exhausted at places like Rutland Water, the London Wetland Centre and Paxton Pits. These birds probably originate from Poland but normally winter in Holland. The Big Freeze has moved them on, only to find that we too are frozen up. They don't stand much chance of survival.

I remember the winter of 1962-63. We had snow pretty well from Christmas to March, and that was in Southampton! Small birds like wrens and Dartford warblers froze to death at night. Kingfishers moved to the coast where the sea also began to freeze. It took decades for the populations of small birds to recover from that one winter.
On the positive side, 1963 (pre-binoculars) brought me my first redwings which I could recognise from my 5/- (25p to you young-uns) hard-back copy of the Observer's Book of Birds or from my 1/3d copy of the Ladybird book. The birds were so starving that you could walk up to them.

I hope it doesn't get that bad, but I also hope we see some unusual birds before it's all over. I'm really enjoying the sight of bearded tits on Rudd Pit and I saw a brambling there today as well. I'd love to see more bitterns, and perhaps waxwings?

On a Health and Safety note. Please keep off the ice. Even if the freeze continues, the thickness of the ice will not be consistent. As a rule, the ice is thicker over shallow water and thinner over deep water, but you can't trust it. Stay safe.