While writing this column, I decided to open the window and let an unusually warm January breeze roll in. My thoughts about an early end to winter were met by a chorus of birds rejecting my proposition. “Uh-uh,” they called. “Uh-uh.” Perfect timing, I thought, and inspiration, because I was writing about my doubting feathered neighbors, the Fish Crow, a smart cousin of the Common Crow and Northern Raven, but with a unique song, an utterance that fills one with hesitation.
Wherever there is water along the East Coast and Mississippi River Valley, or carrion to scavenge in between, you will hear this Doubting Tom of a bird singing away in a cluster of its kin, sometimes with Common Crows in the mix. The Common Crow is—dare we say it–more common, and its familiar guttural, “Caaaw! Caugh!!” is a sound even non-birders can pick out. To the naked eye, there is nothing that readily distinguishes a Common Crow from a Fish Crow, but its call is clearly different. The nasal-sounding song of the Fish Crow is so distinctive that once you learn it, you will never mistake it for anything else. Only an expert can identify subtle physical differences between the two species, so minor that I will avoid mentioning them here (ok—among other tweaks to the basic crow body plan, the Fish Crow is slightly smaller with a less robust beak). Even if you do learn to recognize these differences in the pages of a field guide or comparing images on the internet, you will be hard pressed to transfer what you have learned to what you are seeing silhouetted against the sky in the top of the bare trees of winter. Better to cup your hand to your ear and listen for the distinct nasal serenade.
The name Fish Crow assumes too much, as if this species is what scientists might term an obligate piscivore, a dedicated fish-eater. Like its congener the Common Crow, the Fish Crow will eat just about anything—insects, fruit, seeds, trash, dead fish, other carrion. Being omnivorous is often a path to success for spreading your kind far and wide, scientists find. Think of other omnivores in our midst like raccoons and opossums and how widespread they are. And think about the arrival or eventual residency of a classic omnivore: the North American black bear, followed by another, the coyote. They will be joining us in Cabin John soon.
The tendency for a few Common Crows to mix in with a flock of the more social Fish Crow illustrates a point made in last month’s column: what new marvels are revealed if we only stop, look–and listen. When I started birding around Cabin John many years ago, I didn’t know about the presence of Fish Crows nearby: I had never heard them until a birding colleague pointed them out. Then my life changed for the better.
You can hear them all over Cabin John, even fairly far from the Potomac, although they tend to be more common by the river. The Fish Crow is another example of a phenomenon in some groups of birds where two species look almost identical but can easily be told apart by the songs once they vocalize. More importantly, they don’t interbreed. Maybe they recognize features that we don’t, so they instantly know who is who in the crow community without opening their beaks. We will undoubtedly find more definitive answers with future behavioral studies as to what keeps them separated. Until then, we can only wonder about other species hiding in plain sight that will emerge if we follow the simple instructions for being a naturalist (or surviving life as a pedestrian along MacArthur Boulevard): stop, look, and listen.
By Eric Dinerstein, Contributing Writer
Illustration by Trudy Nicholson, Contributing Artist