Trying to get a photograph of constantly moving, small, high speed fliers is bad enough when they are up in the air. Even more difficult when they are at ground level and rapidly covering the whole field, even coming within a few feet of us as we sat and watched. I tried a few speculative shots with the Nikon and hoped for the best and this was the only one which managed to catch sight of a Swallow:

It is near the bottom left of the photo. All I did was point in the general direction and shoot when they got reasonably close. Far from a brilliant shot but the first I have managed.
It has been estimated that Swallows can achieve a speed in excess of 11 metres per second, 24 mph.