Where have our birds gone ?

We live in rural France, we have a large garden with trees, flowers and shrubs and we are bordered by fields with crops and grazing cows. We are used to having lots of birds in our garden. We have been here nearly 4 years and every year we have had swallows nesting in our barn and great tits nesting in a bird box. This year we have no swallows, barely even seen one, and no tits in the box. Until about 7 weeks ago our garden was dominated by the sound of Chaffinches, now they have completely dissapeared !? We never hear or see Blackbirds any more and no longer see Robins. We have Cherry trees and every previous year when the Cherries are ripe the trees are invaded by flocks of Starlings making an incredibly wonderful cacophony, this year...... nothing..... the Cherries just rotted and fell to the ground :-( Our dairy farmer neighbour informs us that he has plenty of birds including Swallows........ what is going on......... where have our birds gone ? We have several feeding and watering stations! HELP !