Blue Tit Tragedy

A few weeks back I was delighted to see a pair of blue tits take up residence in a box I’d put up in my garden the previous year.  I was particularly happy because I’d made the box myself, to an RSPB design, and fixed it in what I thought was a perfect location, out of the direct sun and high enough not to be bothered by predators or other birds.  A week ago or so I noticed both tits dashing back and forward with food, so it was obvious that chicks had hatched.  My whole family was excited, and we joked about how the tits had struck lucky with their des res accommodation.

Then, a couple of days ago, the parents disappeared.

I work from home, and though my study window can clearly see the box.  I kept looking throughout the day but there was no sign of activity.  The next morning, yesterday, there was still nothing, so I walked up to the box and could hear what must have been at least half a dozen baby birds calling for food.  A heartbreaking moment.

Looking on the web, most advice suggested there was nothing I could do.  Even so, I seriously considered whether I could feed the chicks.  I guess I could, but what then, would I also have to teach them to fly?  Would I just be making it worse?  I decided to do nothing.

As the light was fading yesterday I walked up to the box.  I could hear the babies only now the calls were much weaker.  Today, as I write this, I suppose they’re all dead; I can’t bring myself to go and look.

Now I’m wondering what happened to the parents.  It seems unlikely that both would have been taken by predators or killed in some other way.  Thinking back to the day before they disappeared, I remember a male blackbird behaving strangely on the ground beneath the box.  It was staring up at the tits flew back and forth, and seemed very agitated.  Could it be that the blackbird scared the tits out of his territory?  If so, then that makes me at least partly responsible for this tragedy; I knew the blackbird regularly roosted in the bushes near the box.  Had I had the presence of mind at the time, maybe I would have sited it somewhere else.

Could the blackbird be the culprit?  Is this common?

Damn and blast.