The Northern Rough-winged Swallow summers throughout the Lower 48 and the southern tier of Canada. It forages in open areas, often near water. It can be found from sea level to around 6,500 feet. A few birds usually pass through the Edmonds Marsh each year as this swallow migrates from Mexico and Central America to its nesting territory. Willow Creek should provide nesting opportunities but this swallow usually just passes through. This year has been different. Several of these swallows have been observed for many weeks now so a nest site around the marsh is probable.
Flight style of the Northern Rough-winged Swallow is slower and more deliberate than that of other swallows, but with fluttery wingbeats. It flies lower over bodies of water and uses areas that have more trees or other obstructions than do other swallow species. It feeds on a wide variety of flying insects, including flies, wasps, winged ants, beetles, true bugs, some moths, mayflies, damselflies, and spiders. It forages in the air, mostly at low levels. It is often solitary when foraging but will join other swallows at good feeding areas. It has been seen at the marsh foraging alone as well as among the Violet-green, Tree, and Barn Swallows.
Unlike the similar looking brownish Bank Swallow, the Northern Rough-winged does not form large nesting colonies. Sometimes several pairs will nest nearby, but usually a solitary pair selects a nest site. Typically it is a burrow in a vertical dirt bank, such as in the second photo showing an adult bird leaving the nest. It may be a stream bank, a road cut, or a similar bank far removed from water. The adults may dig a 1- to 6-foot long burrow or use an old burrow of a Bank Swallow, kingfisher, or ground squirrel. The nest itself is bulky and located at the end of the burrow. It is made of twigs, bark fibers, and weeds. It is lined with finer grasses and occasionally with fresh horse manure.
There are usually five to seven eggs, incubated for 12-16 days, probably just by the female. Both parents feed the nestlings. The young leave the nest about three weeks after hatching. The Northern Rough-winged Swallow has one brood per year. The adult in the second photo was leaving a burrow that had both an entrance and an exit hole. The parents were always entering the same hole with insects in their bills and then leaving by the second hole with empty bills. This burrow was in a vertical stream bank.
Where did the Northern Rough-winged Swallow get its name? There are tiny hooks on the leading edge of the primary feathers of the wings. Those involved in research or banding projects, who might have this swallow in hand, can run a finger along the edge of the feather from base to tip and note that that it feels like touching a rough file. Some of the traditional collective nouns for all swallows include a flight, gulp, herd, kettle, richness, and swoop. If we were to create a collective noun for this swallow, I favor a rough file of Northern Rough-winged Swallows.
The conservation status of the Northern Rough-winged Swallow is that of low concern. According to Partners in Flight, the population declined by 18 percent between 1970 and 2014. It has experienced wide-spread decline, as have other aerial insectivores such as other swallows, swifts, nightjars, and flycatchers. The causes are poorly understood but could include pollutants, pesticides, and climate change. The number of flying insects could be reduced by pollutants and the use of pesticides. Climate change could alter when and how many flying insects are available.
You can hear a Northern Rough-winged Swallow call, recorded in Skagit County, here: https://www.xeno-canto.org/34055.
— By Carol Riddell
Carol Riddell manages the bird education displays, on behalf of Pilchuck Audubon Society and Edmonds Parks & Recreation, at the Olympic Beach Visitor Station.