We were searching for junco nests when I heard the unmistakable tic-tic-tic of junco alarm chipping. We followed the sound a ways and found a pair of juncos perched on a low branch, alarm chipping for all they were worth. Strange of the juncos to be alarm chipping at us when we were so far away, before, I thought. I wouldn’t have thought they’d see us as a threat from that far away. Odd birds. Directly below the branch with the agitated juncos was a small shrub. “The nest will be in there,” I predicted, showing off for my new field assistants.
And just as I said that, I saw the snake.
For a split second my only thought was, Ooh, and a snake, cool! Then my brain caught up. I snatched up the snake just in time to see two small chick feet disappear down its throat. Four junco chicks, it was, not three: three in the nest, and one in the snake.
In the spirit of nondisruptive observation, I should have left the snake where he was. But I’m partial. I walked the snake a good distance away until I thought he would not be able to find his way back to the nest, and let him go.
I see nests lost to predators all the time. This, however, was the first time I had walked in on the event itself. I was struck by the obliviousness of the surviving chicks, who begged me for food while a snake swallowed their sibling and prepared to swallow them too: such young chicks simply don’t have a large repertoire of actions, I think, and respond to events either by begging or sleeping. I was impressed by how close the parent juncos stayed to the nest, since the snake would have been a danger to them too. I was a bit surprised to see that the alarm chipping was no more effective as a defense than you might guess: I had wondered if perhaps the birds had some trick that made alarm chipping a meaningful response to predators, but at least in this case, for all the birds’ evident fury, their chipping had done nothing to prevent the snake’s attack.
Well. In this case, actually, the parents’ chipping had summoned a meddling and sentimental ornithologist who removed the offending predator. But that’s probably not a good general strategy for nest defense.