Every year, Eastern Bluebirds (Sialia sialis) take up residence in bluebird nest boxes we have erected on fenceposts around our property.
And, every spring before they return, we thoroughly clean the boxes. However, when we did so today, we discovered a dead juvenile eastern bluebird in one, while another housed a skeleton of what we believe was a tree swallow, since this species had taken over that particular nest box last year.
Obviously, this is distressing, and we wonder what could have killed them. This year marks our 20th year here at Spiritwood, and we have not experienced such losses in previous years.
We have cleaned the nest boxes, brushed them, and aired them. They are now closed and ready to accept new migrants. We never use bleach or any other cleanser on the untreated wooden boxes, which we constructed ourselves. Therefore, these deaths are inexplicable ... and naturally, very sad.
Any comments/suggestions would be welcome.
Meanwhile, we look forward to seeing the nest boxes full of bluebirds yet again this year.