I’ve been getting calls and questions about the huge flocks of tree swallows all over the island over the last couple of weeks. I thought we saw them in these swooping groups only during migration in the fall, but it turns out that they are often found in South Carolina all winter long. We’ve had some fiercely cold (for us) weather lately, but the swallows have stuck around with us all winter.
While I have been calling this behavior a murmuration, based on their swooping and changing direction, I think technically that term belongs to starlings (based on their murmuring sound). Whatever you call it, it’s pretty amazing. If you didn’t get enough swarming in that 1 minute informational video, here’s a MUCH longer one with the uncut footage. Mind you, much of this is in actual freezing rain, so these birds are hardy little dudes. But I have watched it three times now, and it’s really mesmerizing!
It seemed like a strange time of year for them to be here, so I did a little research on ebird, which lets me look up the bar chart for a specific species on Dewees Island over time. As you can see from the chart below, they have actually been seen in all the winter months here.
Diversity of food types leads to more flexible locations
Tree swallows don’t need to head all the way to the tropics for the winter in search of insects, because they have adapted to eat vegetation as well, particularly the berries of wax myrtle (aka Southern Bayberry). The berries provide fat and fiber for the birds, the birds help disperse the seeds elsewhere. In all of the videos on this page, the birds only land on the branches of the wax myrtle.
I owe a friend an apology (JM), because I thought his murmuration photo was a flock of small shorebirds called Dunlin, which would be more likely on the beach right now, and they also fly in flocks that move like a bird with one mind. BUT I was totally wrong: the huge flocks that are landing on the beach and on the wires nearby are all tree swallows! The beach is also lined with wax myrtle shrubs, so they are staging right on the sand and flying around the beach overhead.
Tree Swallows nest north of here
The range map of tree swallows from the Cornell Lab of Ornithology’s All About Birds site shows the breeding range in orange, the migration range in yellow, and the winter (non-breeding) range in blue. They are cavity nesters, and if you live in their nesting zone, you may be able to attract them to your back yard. Here on Dewees Island, we participated in an experiment to see if we could attract them to a string of bird boxes on our berm, but we were unsuccessful in attracting them this much further south of their normal nesting range.
We were lucky to get to watch some breeding pairs and their young this summer in Montana. There is a series of nest boxes ringing a pond, and we delighted in watching them feed their young and bathe in the pond.
Fall Arrivals: Migration season
We have loved watching the tree swallows murmurating and swarming overhead. They’ve been over by the pond where island kids are doing a one-room schoolhouse during the pandemic, so they’ve had a front row seat to some dizzying acrobatics. Tree swallows are almost all white on the underside (Barn Swallows, which nest here, have a darker throat) and their tails are squarish in flight. (Barn swallows have a more pronounced fork in their tail).
After a few days of trying to capture them in flight perfectly, I gave up and asked my friend Craig Watson for some pictures of them perching to demonstrate just how gorgeous they are. This shows them sitting relatively still.
They’ve been taunting me as I spend hours wrestling with the focus and exposure on my big lens. I did manage to get a few in flight.