Recognized across Wisconsin as a sign of spring, and also as a sign that one is mowing the lawn, the barn swallow's ubiquitous swooping displays light up spring and summer with a gasp of orange, solidly worn across its breast.
Arriving from mid-April to mid-May, barn swallows bring their impressive aerial maneuvers to Wisconsin's cityscapes and farmsteads. As a a species, the barn swallow has adapted remarkably well to human development, with more structures providing more nesting habitat for the barn swallow.
Researchers in Nebraska have even discovered evidence that these highly adaptable swallows are evolving rapidly due to both human-caused and natural events. The human-driven change occurred in cliff swallows, where over the past 30 years a population living near highways has exhibited declining wing feather length. This is an example of survival selection, with the longer-winged swallows being struck by vehicles because they are less maneuverable and acrobatic.
The natural-driven selection occurred in May 1996 during a nasty spout of weather on the Great Plains.
During cold, low pressure days, swallows will feed low, along wetlands and ponds, picking insects off the surface because insects are not forming swarms like they would on warm high pressure days. This form of feeding is less efficient for the swallows, and can result in significant energy losses.
After these late-May storms, two thirds of the population died, but the third that remained had shorter wing feathers, tail feathers, larger skeletons, and were perfectly bilaterally symmetrical. These traits all made the swallows better fliers (more adept at picking those insects off the top of the water) and allowed the birds to store more fat on their bodies, which meant they could live longer during those cold spells when food is scarce. You can read more about this phenomenon on Chris Helzer's excellent blog here.
Here at Faville Grove, barn swallows are common near human dwellings. Under my deck, a pair laid four eggs, with all four chicks fledgling. Clutch size is typically 4-6 eggs. Double broods are common in barn swallows, and just yesterday I saw a pair copulating on the wire above my garden, almost certainly a second brood.
The birds will often dive bomb our summer interns once a clutch has hatched, always coming centimeters from a hat, but never actually colliding. With that forked tail, barn swallows are some of the most acrobatic swallows, and deftly maneuver above the Prairie Lane driveway for insects. One particular swallow joined us for lunch as she glided above the deck, stopped, grabbed an insect, and turned away—a breathtaking display. Another juvenile swallow recently tried to become roommates with me, but his bad bathroom manner led me to coax him out with a broom. You can't miss this breeding Wisconsin resident.
Written by Drew Harry
Faville Grove Sanctuary land steward