No swallows, very few sparrows

Amidst the pleasure of seeing the new regular visitors to the feeding station, namely Blackcaps and Siskins, there is concern at complete lack of Swallows on site this year and seemingly just one pair of Sparrows. In every previous year there have been typically half a dozen Swallows hawking over the fields and multiple broods being raised in the barn. There have also been at least three Sparrow nests under the eaves at the front of the house. This year there are no Swallows as of today. I saw a couple at the top of the lane towards the end of April but nothing on site. Similarly there are no Sparrows nesting in our roof and just the occasional visit to our feeding station. I guess the weather being weird in the UK this winter means it probably was weird all over and that may have messed the Swallows up. In any case it is disturbing and it doesn't explain why the Sparrows have also fallen off here.