Thermals

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Between Christmas and New Year we had, at last, a couple of bright days. December being one of the dullest on record. At the farm it was a chance for the buzzards to use the thermals. They would welcome this opportunity to use these currents for a spot of static soaring as the energy they save whilst hunting in this way is substantial. A Buzzard will reduce its energy consumption by as much as three quarters by soaring rather than conventional flying using flapping flight.

A thermal is actually a pocket of heated air that has been warmed by a source on the ground and can be influenced by factors such as dampness, moisture content and the speed of the air across the ground. They occur more readily over open areas of dryer land and the temperature rise that will initiate the pocket need only be of a degree or so above that surrounding it for the thermal to rise; the higher temperature producing air of a lesser density which is therefore more buoyant, but  as soon as the temperature reaches an equilibrium the thermal breaks down. Soaring birds, such as the buzzard, have adapted well to these currents having broad wings which enable the up current to lift them effortlessly.

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For flight shots that are against the sky there is nothing better than a clear blue day. Generally it’s better to slightly over expose in these situations, particularly if you are using a matrix metering system and the bird is fairly small within the frame and has a darkish plumage, as with the Buzzards today.  With the likes of Gannets, and similar lighter species such as the gulls, however, this may result in a ‘burning out’ of the highlights. A simple quick check using either the ‘marching ants’ or the invaluable histogram, will give you this information immediately; another great advantage of using digital.

There is a corner of a field towards the entrance to the farm that has a few mole hills and often when leaving I see a light phased Buzzard either on one of the telegraph poles or on the ‘hills”. It will be searching for worms in the recently turned soil. On this occasion using the car as a hide, I parked up and waited until it appeared. It wasn’t long before it showed and although the light by this time had deteriorated I focused on the bird as it was feeding and waited until it took flight, firing off a couple of rapid frames during the first movements that indicated it was about to move. I had a few attempts over the hour I spent watching, as it would regularly fly over the road into the adjacent fields before returning. The majority of the images are exhibiting too much blur but one or two, and it’s always about percentages, are working well. I was working with the 500mm with the lens fully open and on 320th sec.

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A couple of peregrines also seemed to be enjoying the warmth of the early part of the day and rather than flying with their usual intent over the farm they stayed with the buzzards for a short while, their underparts gleaming white against the blue. They were always higher than the Buzzards and really a little too far off to photograph, but you have a go regardless! Groups of Redwings and Feildfares are constantly moving through at the moment with parties of up to thirty or so in mixed flocks.  A group of six Lapwing flew over and as they represented a new species for the farm I was more excited about them than the Peregrines! The feed is going down rapidly at the moment with all the usuals around and we seem to have a least three Green Sandpipers on the river.

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