BLUE TITS ATTACKED BY SPARROWS

Question

Hope someone can help!! 
 Sparrows have attacked my blue tits nesting box they have removed and destroyed 4 of 8 eggs. They are stopping the blue tits from going back to the nest box. Does this mean the eggs remaining have died? How do I stop the sparrows from attacking the nest box? Please help it was very distressing to see broken eggs. 
 
 Many thanks

Sheena · Answer

Hi Chris, 
 It sounds as if the Sparrows are taking over the nest .It also sounds to me that the entrance hole is too big.We had Bluetits nesting for several years back home and the Sparrows never interfered with it.Sadly, it is nature and i can understand why you are upset..All i can suggest is that you check the size of the hole It should be no bigger than 25mm.