I'm no expert but would expect that the rain and reduced flying insects would be to blame. Have had reports of dead (probably starved) young House Martins which may be a result of the incessant downpours. Swifts obviously start to nest later than HM, and they do fly further (much further) to feed, but they won't be able to completely avoid the effects of all this weather. Hope their delaying strategy is successful.
Swifts have nested in my next door neighbours house for the last 11 years,at least. This year the Swifts returned but didn't appear to nest. I watched them flying around the neighbourhood but they didn't take up there usual nest site. However in the last few days they have started flying into the usual roof nestsite and i'm sure i can here young birds in there. This seems very late for Swifts to be rearing young, there was no earlier brood at this site. Is this unusual or down to the wet weather and the lack of insects on the wing? Either way they're gonna have to raise em quickly to get them airborn for the trip to Africa.
