ferocious house wrens
Perhaps putting up a wren house was a bad move. An article on the aggressive and destructive nature of house wrens is here, at an Audubon Blue Bird site. I have an enormous racket in my backyard often times now: the battle of the house wrens and the house sparrows.
Last week I posted photos of baby house sparrows ready to fledge. I never saw them after that day. But rather than attending to their family, after that day the sparrow parents have been battling the house wrens.
I perhaps should not worry that it is only sparrows that the wrens are fighting with, but the Audubon article suggests that no other birds nests are safe within an acre of a house wren nest. Sparrows are also very aggressive and will destroy the nests, eggs and nestlings of other species in their territory (see this Cornell article). Sparrows and house wrens are both believed to be factors in the decline of the Eastern Bluebird.
I have been moving the sparrow house progressively further from the wren house. But on my 1/8th acre property, I can't go very far. So, I listen to the battle noises outside. I just want them to do their job and eat the bugs in my garden!
garden birds (Hortus Aves)