Swallows are not the biggest of birds, probably about seven inches in length, but even a bird of that size must have clocked up a good few hours in its flying log to be able to fly through gaps of at most five inches between the metal bars of a gate.
Most years there are ten or twelve pairs nesting under the eaves of the house or in the outbuildings, but this year two pairs have elected to build their nests behind the bars shown in the above photo.
Why any right thinking bird should decide upon such an awkward nesting site I have no idea. Not that this quartet of swallows appear to have any difficulty with the locus. There is no hesitation or deviation in their flight and they do keep repeating their aerobatics as they bring back food for their noisy broods. Whether the fledglings will in due course be sufficiently adept to exit through the gaps remains to be seen.