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I've been using a 1DMKII, and even in AI servo, i've missed shots of seagulls, not by a lot. But then again I only use center point, but again I had my 100-400 in IS mode 2 as well. Some have said it works better without IS for better lock on.
Even then I had to keep hitting the shutter button to stay in focus, but this is also been in cold conditions. Not extreme, but usually below 20F.
If you were using centre point only, it is more likely that you did not keep the focus point on the gull. You can check that using DPP.
It is also very doubtful that the temperature had anything to do with it.
Unless you can prove it was the gear, don't blame the gear.