Birds can become a problem when the fruit is ripening, particularly on apples, pears, cherries, plums and greengages. Wasps then exploit the bird pecks and can completely hollow out the fruits.
How to prevent bird damage
The only way to prevent damage by birds is to use nets. This requires prior planning because the trees have to be small enough to make nets a practical option. Read an article about fruit tree rootstocks and tree size.