No, they're not dead. At least I don't think they are. But they're gone.
Yesterday morning the wrens were chattering away, with the mom and dad feeding the babies in their usual frantic fashion. Last night when I got home from work it was quiet, although I thought I heard the chattering of a wren in the next yard somewhere. I figured they had gone to bed for the night.
But this morning, when they were usually highly active, there was silence. The bird house was still hanging on the back of the garage, but there was no chattering emanating from it. No adult wrens flitting back and forth with moths in their mouths. Nothing but silence.
Could the cats have killed both parents and all the babies starved to death in one day? I tiptoed over to the bird house with trepidation, worried that I'd find a bunch of dead baby wrens inside. I peered into the hole but there was nothing but silence and emptiness. No baby wrens.
I went inside and Googled "wren life cycle" and found a thorough article on the House Wren. Sure enough, it said that the incubation period for the eggs was about 13 days, and from birth until the babies were fledged was 12 to 18 days. The timing is right. The wrens have flown the coop.
Apparently House Wrens are quite prolific and actually produce two broods per summer. So the first one has to get up and out so they can start working on another one.
I am sure I heard the chattering of a wren nearby this morning so they must be around somewhere. According to the article, once the breeding is over they are much less conspicuous and much quieter.
I expect they don't produce their second brood in the same place as the first so I guess my days of sitting on the deck in the morning hearing the chattering and singing of the wrens are over. The silence is a little sad but now I hear other birds that were drowned out by the wrens. And today I heard the first cicada. The cycle of life continues.