Bird food

Because of the light and shade caused by the trees along the canal there are patches where the sun shines on the canal but the background is dark. Often at this time of year, in these areas, you can see flies going back and forth in streams of thousands.

Out in the sun, where you see Swallows flying along the canal, it is much more difficult to see the flies but I could imagine that there would be just too many. A Swallow would only want to pick them off from round the edges. Perhaps that’s why the flies do it.