Who thinks of swallows in midwinter? Well, this friend does. He lives along the coast in what you might call the Dun Laoghaire area. He writes that in 1977 they had no swallows along his sea-front and he and neighbours missed their chirping and aerial acrobatics. He deduced that the reason was that at their normal arrival time we had lots of east wind which blew the flies away. So the birds had to leave the coastal area and move inland to eat. He discussed this with neighbours and they agreed, not experts all, that such could be the reason. In the spring of this year the swallows returned "soaring over my garden, adding much to the ambience, and, as I took some note of the wind directions at their arrival time, my theory was hardened. The winds were mainly south-west and north-west. But I was only partly right. At an open day at Bull Island I asked a guide if my theory held water. The answer was `not quite'. For at the points where the swallows left the North African coast there were strong northerly winds that beat them back from moving northwards. So the swallow numbers in those regions went up and ours went down."
This impressed our friend greatly so he asked another swallow question that had been in his mind for years. "Why," he asked, "do the swallows bother to come to Ireland when I have seen plenty of flies in various countries in Africa which I have visited?" The expert agreed up to a point. "But here there are many more flies, and as the swallows expect to lay more than half-a-dozen eggs, there would not be enough flies for all the offspring if they remained and nested at the Cape." And here is the part of the story that many of us have perhaps not thought of, for when our original correspondent asked if they did not all fly back there, the reply was: "No, they may all set off to fly southwards, but only a small number survive the trip, and there are just about enough flies waiting for the survivors."
The average person seeing the gathering of swallows on the phone lines as autumn comes on would probably assume that, short of terrible storms or other dangers, the vast majority who went off home (or is Ireland home to them?), anyway, southwards, would arrive safely. So there you are: "only a small number" make it down to South Africa.
Gilbert White of Selborne wrote in 1772 that in November on a chilly day he saw three swallows flying around and this induced him more and more to believe "that many of the swallow kind do not depart from this island, but lay themselves up in holes and caverns; and do insect-like and bat-like come forth in mild times and then retire again to their latebrae" - i.e.. hiding place or retreat.