I have a 40D camera and a 400 f5.6 prime lens.
Today at a local patch a pair of Hobbies put a great display and I took loads of shots however,despite me having the exposure compensation set at + 1 1/3,allmost all of the shots were badly underexposed and beyond saving.It was not that bright a day.Two examples attached.
Other settings used : spot metering,AI servo,centre AF point.
Should I have had the exposure compensation on maximum.Any advice would be welcome.
Max.
I can't directly answer your question but this is an ongoing thread that definitely will give you some information on the subject of focus & exposure for BIF photography.
http://www.birdforum.net/showthread.php?t=113374
Spot metering isn't always the best option, Max - in these situations it's very hard to be so accurate with the camera that the "spot" of the metering sensor is directly on the bird.
Instead, the camera is much more likely to meter off the sky, under-expose it (relatively speaking) to bring it down to 18% gray or thereabouts, even with positive EC dialled in, which will under expose the bird.
So...
Suggestion 1 - shoot RAW. I suspect that these pictures would actually be recoverable (ish), and RAW maximises your chances.
Suggestion 2 - get onto Evaluative metering, which will meter from the whole scene and produce a more evenly exposed end-result (in theory anyway), or Partial metering, which is actually recommended for situations where the background is much brighter than the subject.