Bluebird Trail Monitoring Does Have Heartbreaks

While monitoring the Vredenburg Trail is usually a very positive experience, there are times when one encounters a nesting incident that can be discouraging.

On June 19 while monitoring the trail with his wife Chris Reid, Denny Granstrand had a jarring moment when he lifted the lid of Box 65. I imagine that like most of us, his pupils enlarged, breathing stopped, and he took a quick step back to recoup. (Editor’s Note: According to my wife, it was actually a fairly lengthy leap backwards!)

After composing himself and considering his options, he stepped back up to the box and snapped the photo below.

Image - Pacific Gopher Snake in Bluebird Box 65 - Denny Granstrand
Pacific Gopher Snake in Bluebird Box 65 - Denny Granstrand

Denny later identified the intruder as a Pacific Gopher Snake. They resemble rattlesnakes; I have tagged them as bull snakes but a bit of research indicates that name is more often applied in the east than out here in the wild west where gopher snake is the moniker of choice.

This is the fourth time a snake in a nest box has been relayed to me. My mentors counseled me that when eggs or nestlings disappeared from a box with no evident disturbance of the nesting material, a snake would be the likely culprit.

Personally, I have seen a snake draped across the lid of a box once and a few slithering away in vegetation below the boxes on a few occasions. In the Wenas area, I have been checking nest boxes for twenty plus years. During that time, I estimate that I have lifted the lids of boxes at least 40,000 times. And I have yet to hit the jackpot of a snake inside the box.

But getting back to the story of Box 65 this year. The week prior to Denny and Chris’s visit, six nestlings sporting tail feathers (estimated age 14 days) were recorded in the box. In the photo, one can see plenty of blue beneath the snake.

I visited the box three days after Denny and snapped the photo below.

Image - Bluebird Feathers in Box 65 - Richard Repp
Bluebird Feathers in Box 65 - Richard Repp

As you can see, there are many feathers. Not the clean, undisturbed nest that one might expect. I opened the box, pulled the nest out and placed it on the ground for further inspection.

Perhaps my remorse at losing six nestlings so close to fledging caused a lapse in my rudimentary CSI investigation. Still seething about the snake and dealing with an infestation of beetles and insects in moist, ripe body parts, I did note that one corpse was really dried out. Probing with my putty knife revealed three other fresher nestlings. Did the snake just ingest two of the six?

Later at home, it occurred to me that perhaps the snake was drawn to the box by the odor of decomposing nestlings. An internet search stated that snakes will consume carrion.

My conclusion is that perhaps the smallest nestling died naturally and then the nest was attacked by something that killed and partially plucked three others. Did two fledge prior to the attack? Or did the snake consume two…dead or alive? And was the attacker avian? Though very unlikely, the best scenario would be the snake arrived as mayhem prevailed and devoured the heinous villainous attacker.

It will be interesting to see what transpires in the ensuing weeks. Though what follows at this box will be circumstantial, perhaps some light will be shed.

My thanks to Denny and the imagery that smart phones are able to convey. Oh, and the sponsor of Box 65 . . . Lucky Hall!

-Richard Repp