Abandoned?

Isn't it elegant? I found this nest in one of my 13 nest boxes  -  one of a pair situated near the county road. I had seen two babies fledge from here about a month ago and I'd thought there were more. It's possible that the three eggs in the bottom were from a later attempt at raising a family. They are tree swallow eggs and the nest is a typical tree swallow nest.

I thought this so beautifully crafted, the bottom made of grass and straw and then topped and lined with all the different kinds of feathers dropped by the many birds in this area - notice the two little woodpecker feathers at the top and there appear to be crow or grackle, mourning dove and gull at the very least, all neatly woven into the whole. A soft downy place for little ones to develop. I replaced the nest after I'd taken the photograph, just in case the parents are still around, but frankly I haven't seen a swallow in my boxes for some time... and if they're around they're catching insects and building up their strength to fly south.

It makes me wonder why these eggs were abandoned? Were the parents killed by a predator, did the eggs die from the heat? If that's the case how do birds know this? Or were the eggs not viable - just a female laying unfertilized eggs? A mystery that I'm going to pursue with one of the fellows who is a biologist and lives nearby. If I find out - I'll let you know.

Meantime, enjoy the birds of summer - the goldfinches are back at my feeders after raising their families, the hummingbirds are busy as well, and I have a family of bluejays and another of grackles that scolds me if I don't set out seeds for them on one of the tables in the yard. Others in my neighbourhood are enjoying their feathered visitors as well, doesn't watching birds make a fascinating pastime?