2017-05-24 / Columns

A Bluebird Nest Box Tragedy

by Dan Stiles Wildlife Biologist

Can you figure out this wildlife mystery, before you read the answer at the end?

A few evenings ago, my wife and I noticed an almost whirlwind of many bird species flying in circles and squawking their various alarm calls around our closest bluebird nest box. I knew that a pair of bluebirds had an active nest there, and had watched the parent birds feeding their youngsters for several days.

A half dozen mockingbirds and an unusual number of purple grackles were flying about frantically, so I thought probably the nestling had just left their nest, and these interlopers were intent on consuming them. I know for sure mockingbirds and grackles are worse than mischief makers in the songbird world.

We have an American restoration chestnut tree close to the nest box, about 12 feet tall with very dense foliage, where I assumed the nestlings had taken shelter following their first flight. But, I could not find any of them. Meantime, eight or 10 upset male and female bluebirds, more than I have ever seen in our back yard continued to call frantically and fly into the branches of our chestnut tree. It may be hard to believe, but there were very unhappy sparrows, robins, chickadees and for sure other bird species constantly whirling about.

I do know that when tree swallow youngsters leave their nest box, quite a few of their relatives and friends are present to welcome them, or so it seems. It appears that tree swallows celebrate the newest arrivals of their species. I suspect there is a wildlife contest between predators who are intent on consuming inexperienced nestlings when they first leave the nest, and their own species, intent on doing all they can to protect them. In my experience, when one nestling leaves the nest, almost immediately all the others follow.

Usually youngsters that leave their nest are easy to locate. The parent birds fly and perch close to them. Besides, they look lost and vulnerable as they surely must be. But, I could not find any of them on the branches of my American chestnut tree, so I returned to the nest box. To my surprise, there was a five inch long, pencil sized snake like object protruding from the entrance of the nest box opening. I photographed whatever it was, and suddenly it disappeared within the nest box. And, many bird species continued to fly and squawk around me.

I needed a Philips screwdriver to open the side of the box, because it occurred to me that perhaps what I had seen was the tail end of a much bigger snake. Upon opening the side just a bit, I was eyeball to eyeball, facing a big, black (and white beneath) coiled up black rat snake that half-filled the interior of the nest box. I poked and prodded him until he eased out and dropped to the ground. He was about three and a half feet long.

Last year, I had placed this same nest box a hundred yards away on a black cherry tree. Faithful readers will remember that I discovered a huge five foot (maybe more) black rat snake inside, and the nestlings were gone, of course. Black snakes are very rare on our property, unlike around our cabin in Morgan County where they are quite common (as are copperheads), and yet twice different rat snakes found the same nest box. How do they do it? I don’t understand it, because snakes do not see well, hear well, but apparently, their flickering tongue (sense of smell) tells them everything they need to know.

The answer to the question as to the cause of all the bird commotion is that many birds were well aware of the snake’s presence, and no doubt he was highly visible in the daylight hours as he circled up the post that supported the blue bird nest box. Obviously, all species of snakes have no bird friends at all, and all bird species do their best to make any snake’s life miserable.

And so, I am convinced that predator guards to safeguard bluebird nests are essential, even though the likelihood of snake predation seems remote. Black rat snakes are here presumably to lessen the number of rodents, mostly rats and mice. I’m all for that, but bluebird nestlings ought never be on their menu, and predator guards will keep that from happening.

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same activity at our

same activity at our nesting black birds some years ago . the black birds were unsuccessful in defending their clutch of eggs