These black shrivelled pears are probably the work of the winter moth. It overwinters on the ground, then climbs up the tree and lays eggs in the tiny fruitlets that form in spring. The small fruits are probably due to overproduction in relation to ability to fully develope all the fruit that are set. If the tree is large, you still get lots of pears anyway. If it's small you can manage it by removing some blossom at white bud stage or later at June drop time. Summer and Winter pruning helps too. Grease banding the main stem of the tree is said to prevent winter moth from going up and using pears in the life cycle. It would be nice if I could find some at the GC!!