Four Lost Bluebirds...

I went to clean out our Western Bluebird box today and sadly found these frozen eggs from last year abandoned in the nest.
We've had many successful hatchlings fledge and fly from this box over the years but last year something went wrong and these four are lost.
This also happened in the same box about 5 or 6 years ago and, in light of the worldwide decline of songbird populations, it's heartbreaking to think of the generations of birds that will never exist because these four didn't make it.