Quote Originally Posted by Joel Eade View Post
In reality, no matter what equipment you have, some days just aren't made for getting good images of birds. Severe overcast and rain will be very tough no matter what you have. On those days get out your wide angle and tripod for some slow shutter speed landscape work. You can make some lovely images with long shutter speeds and blurred water You just have to take what mother nature gives you and wait for good light to go after the birds.
I use manual mode 100% of the time on birds in flight. You need a fast shutter speed, probably at least 1/1000 or faster, to get a sharp image in most cases. Additionally light is needed and at a good angle to get enough contrast to see detail the plumage. If it is so overcast as to eliminate those two things you will really be frustrated. Rain in the air will only make it worse. But if you are trying it.....I would use manual mode, lens wide open, set the ISO to what is needed to push the exposure to the right without over-exposing the bird. Let the background blow out if you have to. You will get a so called "high key" image but that's probably the best you can do. Then deal with noise in post processing.