There was a considerable amount of flycatching going on in our Wetlands on Wednesday. Besides the local Eastern Phoebes and winter resident Yellow-rumped Warblers (butter butts) sallying forth from their willow branch perches to capture winged insects over the Wetlands’ water, two Northern Rough-winged Swallows showed up. They are aerial specialist, only perching to rest on occasion.
Of the six swallow species you’re likely to see in our area, the Northern Rough-winged Swallow is the one that I’ve most often seen here in the Museum’s Wetlands. They’re certainly not the most numerous swallow in the area, Purple Martins, Barn Swallows, and Cliff Swallows are well represented and probably out number these drab-colored members of the swallow clan.
Unlike the others, rough-wingeds usually nest singly, that is, they don’t form colonies. And, they will nest in open pipes projecting from office buildings, malls, and even storage containers, as well as natural cavities and crevices in rock faces. I’ve been waiting for them to nest in the diabase rock wall of the Black Bear Enclosure since I first arrived here at the Museum some six years ago. I’ve seen them inspecting holes and cracks in the rock of the bear enclosure, but so far, nothing conclusive.
They’re nesting close by though, I’ve seen young birds perched out on the snags of the Wetlands taking swallow lessons from their parents. A good part of a swallow’s life is more than likely instinctual, but a few pointers on hunting technique probably can’t do any harm.
If you’re wondering where the name “rough-winged” swallow comes from, sit back, I’m going to tell you. There are tiny barbs or points on the leading edge of the outer most primary of these birds (the front of the longest feather of each wing). These projections create a rough edge to the wing.
In the male, these barbs are recurved (they turn back on themselves, towards the body). No one knows what the purpose of these barbs are, though its been suggested that they may have something to do with sound generation while in flight during courtship. Other species generate sound with their feathers while preforming courtship flights, why not rough-winged swallows.
Purely out of speculation, they may have something to do with gripping, that is, the hooks may serve as some sort of tool to grip onto something. Since the male’s are recurved, perhaps they are somehow used in the mating process, to hold onto the female. I’ve never witnessed rough-wingeds mate before but I’m going to be on the lookout from now on.
I’ve managed to find a photo of the barbs on the Vancouver Avian Research Centre (VARC) website. I’ve handled Purple Martins and Barn Swallows before but never a rough-winged, so I’d never seen the barbs myself. Thank you VARC, for the great closeup shot of the wing.
I didn’t see the birds the next day, they were probably just passing through. There will be more behind them, others are winging their way north on this very day. Birds of this and many other species are already in motion. More and more birds will be coming through our area. Things will be changing more rapidly as the days go by. I’ll keep an eye out and let you know what happens.