About a year ago, on the way to work, I stopped to admire a Black-capped Chickadee that had landed in a small tree only a few feet away. It watched me while making its “chickadee-dee-dee” call, and I gazed back, feeling grateful that a wild animal had chosen to share space and interact with me.
My bubble burst when I remembered that “chickadee-dee-dee” is the species’ alarm call, and this bird was not feeling at all grateful to be sharing space with a mammal 5,000 times its weight. Duh. I moved on, humbled, but it got me thinking about animal vocalizations and what we know and don’t know. For example, a very cool 2022 study by University of Chicago researchers found that neotropical birds respond to chickadee alarm calls the same way that a Northern Cardinal or Tufted Titmouse would. That is, they innately understand it to be an alarm call despite never having encountered a chickadee in their life. If I hadn’t been feeling so starry-eyed and human-centric that one morning, I, too, may have intuited the call to be one of agitation. Just like human alarm calls, aka yells and screams, bird alarm calls tend to be loud, sudden, emphatic, and not particularly musical. Tuning into them is a great way to tune into the lives of other species.
Mobbing
Paying attention to alarm calls also happens to be a great way to spot birds of prey. Crows, way up there in the canopy, are often the first to spot aerial predators, and when a threat arrives, they want everyone to know. I regularly interrupt myself on bird walks when a group of crows starts going bananas, lest we miss a brief glimpse of a hawk or eagle. Crows’ sentinel behavior is handy for birders and it serves an important role in alerting other species of a threat. This type of alarm call is meant to rally the troops and harass, or “mob” the offending individual.
Mobbing calls are used by songbirds as well; an American Robin’s mobbing alarm call might be familiar. They’re often lower pitched with a broader bandwidth, meaning that they contain a wide range of frequencies. It’s easy to tell where these types of sounds are coming from; this gives away the location of the caller, but also the predator, which is the intended effect.
Sometimes the whole neighborhood comes out to drive the predator away. On a Beginner Bird Walk at Gilsland Farm last month, we watched a perched Merlin being harassed by Cedar Waxwings, American Goldfinches, an Eastern Phoebe, and a Ruby-throated Hummingbird. The Black-capped Chickadee scolding me on my commute was using a mobbing call. That individual didn’t mind that I saw where it was because it knew that I couldn’t move fast enough or jump high enough to catch it (yes, the birds watch us too!).
Chickadees often forage at the tips of branches, making them another handy sentinel for others. Chickadees and their relatives, Tufted Titmice, are often the nucleus of mixed-species flocks in winter, in part due to their excellent cognitive abilities, and because they spot predators sooner than species like nuthatches that forage closer to tree trunks.
‘Seet’ calls
Mobbing is a great strategy when you know that you can get away or the predator isn’t actively hunting, but if in imminent danger, animals will opt for an alarm that isn’t easy to locate. High-pitched, narrowband calls, like the single high “seet” call that many birds use as they dive for cover, are much harder to locate (here’s an American Robin’s ‘seet’ call for comparison). I wonder if this is why I, (and others, or at least others on Reddit), often feel like I’m being haunted by Cedar Waxwings that I can’t find. The high-pitched, thin whistles that they use to chat with one another sound like they’re coming from everywhere and nowhere at the same time. Perhaps this is an adaptation for a species that spends a lot of time foraging in large groups out in the open. They certainly wouldn’t want to lead a predator to the flock as they’re scarfing down fruit in trees and bushes (would a grad student do me a favor and test that hypothesis?).
Those “seet” calls are generally used by birds in response to an aerial threat. You may have heard that squirrels also have different alarm calls for aerial vs. terrestrial threats. You’re probably familiar with the rapid ‘kuks’ and ‘quaas’ (YouTube link) of an Eastern Gray Squirrel signalling a threat on the ground (and that threat is usually, but not always, you).
Slower ‘kuks’ and moans (YouTube link) are often in response to aerial threats. These insights come from thousands of years of indigenous knowledge and scientific studies with simulated “threats.” In a review of squirrel alarm call behavior, Dr. Thaddeus R. McRae, professor of biology at Lee University in Tennessee, suggests that specific call types may be used to express various levels of agitation or urgency, but this doesn’t mean that a scarier threat necessarily elicits a bigger vocal response. In fact, it may be just the opposite. A Gray Squirrel that’s run up a tree is still quite vulnerable to an aerial predator, so it may not want to draw attention to itself with loud, fast alarm calls. When the threat is terrestrial, however, they can safely let it rip at you, your dog, or virtually anything else without wings. In fact, squirrels often face terrestrial threats while loudly scolding them. If you notice a Gray Squirrel plastered to a tree trunk, however, looking up and making slow ‘kuks,’ then you may want to scan the trees for a hawk.
Flush sounds
Other alarm calls are meant to startle. The sudden, loud noises made by flushed Mourning Doves, pigeons, grouse, and American Woodcocks surprise would-be predators. These species spend a lot of time on the ground, where they rely on camouflage (or street smarts, in the case of pigeons) to protect themselves from predators. That strategy works well until a threat gets too close, at which point the bird has to flee. A dramatic exit causes surprise and confusion, buying the bird some time to get away. These explosive noises are made by the birds’ wings, and they, too, contain information about threats, or lack thereof.
Studies have shown that the wing whistles of Mourning Doves fleeing a threat differ from those made during a non-panicked takeoff. This is likely because the frightened take-offs involve more rapid, vertical lift, which vibrates the modified feathers at the tips of their wings in such a way that a specific tone is produced. Fellow doves and even other species of birds react to panicked whistles but not to those made during a casual takeoff.
Diving deeper
The best way to learn to identify animal vocalizations and learn what they mean is to spend a lot of time observing animals. That being said, if you ever have a chance to take a class with a naturalist like Dan Gardoqui, you should do that too! Dan is an incredible guide who we’re lucky to have locally at Center for Wildlife. He contributed to the fabulous book What the Robin Knows, by Jon Young, all about bird language. He can also whip out some startlingly accurate bird calls.
Dan and other students of animal communication know that what we hear as a cacophony of chirps, chucks, tweets, trills, and yelps often communicate a lot of information about what’s out there, what those animals are feeling, and what might be making them feel that way. We may never unravel the complexities of animal language (and many argue that we shouldn’t), but it is possible to tune into animal vocalizations in a way that enriches our connection with the rest of the natural world, and alarm calls are a great place to start, especially when they’re impossible to ignore.
Dan and other staff from Center for Wildlife will be at the Summer Wildlife Mingle at Gilsland Farm Audubon Center on August 13 to present an update from the field of conservation medicine. We’ll hear about current trends in the Center for Wildlife medical clinic, illustrated in part by case studies of recent patients. Then guests can get up close and personal with an assortment of live wildlife ambassadors and Center for Wildlife staff and volunteers. Don’t miss this chance to learn about these incredible animals, the important work of Maine wildlife rescuers and rehabilitators, and what we can do to protect wildlife.
