Last year I had very few cherries on my cherry tree, and those not stolen by the birds rotted. After some research, I discovered that the shrubs and rambling rose growing through the tree were probably to blame as they like lots of air. So I
hacked pruned all the encroaching growth away in spring, and have subsequently been blessed with a bumper crop.
A continual succession of birds visiting the tree also show their appreciation. Once this blackbird has had her fill I'll pick some of the bigger bunches before her relatives strip the tree!