Why Do American Dippers Dip?
by Kelsey Frey
MOSS Field Note #1
American dipper Cinclus mexicanus in Yellowstone National Park. Photograph by Dlthewave
American Dippers (Cinclus mexicanus) are small, slate-gray songbirds with chunky, rounded bodies and short tails. Oh, and they swim.
As “North America’s only true aquatic songbird,” I often see these plucky passerines (any bird of the Order Passeriformes that include songbirds with feet adapted for perching) precariously perched on piles of debris in the middle of a rushing river, diving in and out of the water to catch aquatic larvae, insects, and occasionally invertebrates. It’s fascinating to see these little birds swimming amongst the rapids (technically, they dive in and walk along the streambed, propelled by their wings), in part because it seems so wrong. How can something so cute and fluffy also be so badass?
While I’m not sure we’ll ever get the answer to that question, there’s one other behavior that this bird does that intrigues me. Every time I’ve observed them, I notice them constantly bobbing up and down. This unique behavior is called “dipping,” and is what dippers are named for. That means it must be pretty important, right?
If you’ve never seen this behavior in the wild, I’ll describe it to you: They bob their entire bodies up and down, bending their legs to crouch down and straightening them to stand back up, almost like they’re doing squats. At the same time, they may bob their tails or stretch out their wings. They dip faster when they’re either disturbed or excited, up to 60 times per minute (that’s some fast dipping!).
And, from what I’ve noticed, dippers dip a lot. They’ll engage in this movement while feeding, during courtship rituals, and when agitated. And now that I think about it, I’ve actually never seen a dipper sitting still. They’re constantly moving - either walking, swimming, flying, and, of course, dipping.
I contemplated the reasons behind this behavior. Birds already have good enough balance, so I doubt that this motion is helping them stay upright. Since they do it as part of courtship rituals and when they’re agitated, it could be a form of communication, but I’ve also seen them dipping while they’re alone. To me, the most obvious answer was that it was helping them hunt - but then why would they do it even when they’re not trying to catch food? Maybe it serves multiple purposes, since they dip during so many different activities.
With these questions in mind, I turned to the internet to determine the reason for this mysterious behavior.
I came across several plausible theories for why dippers dip:
Hides the bird from predators: The moving water and moving dipper helps it camouflage
Helps it spot prey under the water: Vertical eye movements can help the bird measure the location of food (triangulation), as well as help the dipper better see into the water
Serves as visual communication in a loud habitat: Dipping can be a way for dippers to communicate their location or send warning signals to other dippers, be a sign of fitness, or warn predators
It turns out that the third reason holds the most promise according to research, especially since these birds often dip during courtship rituals and as a way to scare off potential aggressors (for example, they dip while competing for roost site, territorial advertisement, territorial defense, and alarm over human or predator intrusions). As Wild About Utah, a Utah public radio production puts it, “Dipping could be used to convey messages such as ‘Go away, this is my territory,’ or ‘Hi, I would like to mate with you.’”
However, there’s still the fact that Dippers still do their characteristic bobbing behavior even when they’re alone. In addition, fledglings also dip when they’re in the nest, and wouldn’t need to really use the behavior for any of the reasons mentioned above.
Side note: In case you’re wondering how they dip during the courtship phase (I was), according to The Cornell Lab of Ornithology, the “female begs, crouches, flutters wings, and gapes like a fledgling; male then feeds her; both birds dip during this activity.” This is the second phase of the courting process, after Proximity Tolerance (birds feed close to each other for a couple of months), but before the Singing and Flight Chase phases.
And one other interesting piece to the puzzle - the White-capped Dipper (Cinclus leucocephalus), a South American dipper species, doesn’t dip at all! This may be one of those things in science that remains somewhat of a mystery. Maybe we’ll never know for certain why these birds participate in this distinctive behavior. Perhaps one, or more, of the current theories is correct. Regardless, I’ll continue to observe this fascinating behavior and come up with more of my own theories.
References:
American dipper overview, all about birds, cornell lab of ornithology. (n.d.). Retrieved May 8, 2022, from https://www.allaboutbirds.org/guide/American_Dipper/overview
Why dippers dip. (2013, September 30). Audubon. https://www.audubon.org/news/why-dippers-dip
Behavior—American dipper—Cinclus mexicanus—Birds of the world. (n.d.). Retrieved May 8, 2022, from https://birdsoftheworld.org/bow/species/amedip/cur/behavior
VanZanten, C. (2017, February 6). Why dippers dip. Wild About Utah. https://wildaboututah.org/why-dippers-dip/
Behavior—White-capped dipper—Cinclus leucocephalus—Birds of the world. (n.d.). Retrieved May 12, 2022, from https://birdsoftheworld.org/bow/species/whcdip1/cur/behavior