One of the bluebird boxes has been playing host to a new family of eastern bluebirds (Sialia sialis) this spring, but I’ve been too busy to do much about it. Still, I was trying to keep an eye on it to possibly catch the emergence of the fledged youngsters, something I’ve missed every time previously. Many birds will bail the nest but spend time on the ground and low branches, learning how to get control of their flight surfaces, but bluebirds apparently get through this stage pretty quickly, like within hours at the most. So I took a peek in the nest box this morning to see how well their feathers were developed, to determine if I should try to set up a camera trap. What the flashlight revealed was that I needn’t bother with this brood any more.
That’s a black rat snake (Elaphe obsoleta obsoleta,) not a terribly big one as far as they go – while they can reach two meters or so in length, I’m guessing from the size of the head that this one is closer to one meter. It had consumed all of the bluebird fledglings, and was crassly using the box as a safe haven to digest its meal. It was well aware of me opening the box for the pics, and was simply holding still in the hopes that I’d go away.
Some of this is perhaps our fault. We’d placed two nest boxes on stumps that had once been huge bushes, which the landlord’s inept assistants had hacked down to some strange modern sculptures – I suspect they misinterpreted their instructions, since the pampas grass in the yard needs to be cut back to nothing each winter. It’s a grass, it grows back; the bushes didn’t. But it means the nest boxes were placed lower to the ground on a handy climbing surface, and black rat snakes are serious climbers.
The adults were definitely confused by this development. They chattered quite a lot more than I usually hear them, and made repeated attempts to enter the box, usually hovering just outside for a few moments – you can even see this one is bearing food. They had to be aware that there was a snake in the box, and they were in as much danger as their young, but it hadn’t overcome their feeding instincts. They don’t have a lot of time to get over this; snakes can consume a lot of food when they want to, letting it cover them for days, weeks, or even months at a time, and if this one decides it can squeeze in an adult, it only has to strike while one of them peeks into the box again.
Had I discovered the snake before it found the young, I might have intervened, moving it to another location – or maybe not; this is how nature plays the game after all. But at this point I’m just leaving the situation as is – another thing The Girlfriend might be displeased with, since she’s not fond of snakes. Yet the damage is already done and the snake has likely lived in the area for at least a couple of years, judging from its size.
As a quick note, if you really want to avoid this fate for any bluebird boxes you erect, about the best you can do is use a freestanding pole, at least 150 cm (five feet) in height, with a squirrel collar well beneath the box. Just about anything else is able to be circumvented by snakes. Or you can take it all as it comes, circle of life and all that – predators routinely thin out the bird populations, and this has been going on for a long time. Our personal feelings towards cute birds and evil snakes isn’t going to improve on it at all, and is in fact pretty self-centered.
Update: Appearances can be deceiving.