As a bird biologist who studies bird songs, I immediately recognize most sounds I come across in nature: the winnowing of a Wilson’s Snipe, the smack of a Dark-eyed Junco, the zee-chubbity-chub of a Rufous Hummingbird, just to name a few. For me it is a matrix of sound, as diverse and varied as the surrounding landscape. When I hear a strange sound in nature, I can’t give up until I determine its source.Some years ago, while working in the Big Creek area of the Bitterroot mountains, my aim was to conduct counts of songbirds while keeping my eyes open for woodpecker nests. The area had been torched by severe fire in 2003 and many woodpecker species were abundant there. I had just come up a steep mountainside on the edge of the burned forest, when I heard the familiar foraging sound of a woodpecker. Tap, tap, tap. Aha! Here’s my bird, I thought. But where was it? The only species present was a Clark’s Nutcracker sitting in the very tree where the woodpecker foraging sound was coming from. Could it be?
Nutcrackers belong to the family Corvidae, who are masters of vocalization and are known for their ability to mimic other species. It turns out there was no woodpecker at all. This “mock-foraging” sound was coming from the nutcracker. I imagined all sorts of reasons behind this strange vocalization: mimicry, competition, just a bird experimenting with new sounds? It is impossible to say, but a crop of pine seeds was at stake, not to mention the protein-packed, irresistibly juicy beetle grubs that lie under the surface of fire-scarred tree bark. An opportunistic omnivore’s feast. If competition was playing a role, then the nutcracker’s “mock-foraging” sound was a message to other woodpeckers to “stay out.” In the Sierra Nevadas, Clark’s nutcrackers have been known to display dominance over other woodpeckers, and, given the intelligence of this species, the “mock-foraging” call note probably wasn’t without a purpose.
Fast forward two years, and I am hiking near a local recreation area. I hear another bird vocalization I am unfamiliar with. A hollow, guttural Cr-r-ruck. This time, I immediately believed the sound to be corvid-like. As I approached the area, my suspicions were confirmed. Since it was not the usual call note of a Clark’s Nutcracker, I wondered what information the bird might be trying to communicate. A few steps later, I encountered the reason for this strange vocalization: a male Merlin was inconspicuously perched in the pine below. This small, yet powerful falcon was no longer in hiding. Presumably, all animals in the forest were now aware of the exact location of the Merlin due to the capability of the nutcracker to communicate this predator’s presence.
Biologists have studied call notes of corvids ardently. Corvids are masters of manipulating and reproducing sounds. Clark’s nutcrackers have a large repertoire of calls; researchers have described up to 13 distinct call notes in this species. Variation of these calls is also known to be present among individuals. Other corvids, such as ravens, have over 30 known distinct calls. The ability of corvids to have such a wide range of calls is thought to be related to their cognitive capacity. They are perhaps the most intelligent of birds, and among the most intelligent of all animals in the world. With such a wide range of communication and meaning behind their calls, it makes one rethink the meaning of a “bird-brain.”
"Field Notes" is produced by the Montana Natural History Center.