Eldeberry blossoms

I checked the bird houses today w/ mixed results.  Most of the tree swallow chicks are fully feathered and will be flying within the week.  I should really have left their houses alone since there is a danger of frightening the chicks so much that they might attempt to fly too early.   I checked them because I thought the chicks should have already been old enough to fly.  I seem to have some of the most laid-back chicks I've ever seen though and they all just sat still.  The bluebird chicks have already flown off so I cleaned out the house in case someone wanted to have a second brood.  Found another house w/ brand new bluebird eggs so it might be that those bluebirds have already started in a new location.  The bad news was two nests contained dead tree swallow chicks.  They had lived long enough to develop feathers so I don't know what happened.  Same thing happened in another bird house two weeks earlier.  In all of the years I've been checking the houses I've never lost chicks that far along.  I was talking w/ my neighbor Doug Dearhamer and we were considering various possibilities - one or both parents were killed or not enough insects to keep chicks fed (it has been rather cold for insects).  I considered parasites or disease but the houses are quite far apart.  I'll look on-line and see if I can find anything like that just in case.