Tuesday, April 19, 2016

Northern Rough-winged Swallow

Northern Rough-winged Swallows are second only to the Cliff Swallows in breeding distribution in San Diego County. They are found throughout the county west of the deserts and below the highest elevations. However, while they are found in more places, they are less numerous than Tree and, perhaps, Violet-green Swallows. They winter in small numbers and are very early migrants, so chances are there are some on most of your day's birding lists.

Northern Rough-winged Swallow
Northern Rough-winged Swallow. Ramona, California. March 27, 2016. Greg Gillson.
And what about those rough wings? The outer vanes of the primary feathers have recurved hooks or serrations. My references aren't clear, but it may only be the outermost primary wing feather and only males. Here's more about it from the Eastside Audubon newsletter of July 2014.

Northern Rough-winged Swallow
It is mentioned in some texts, but here's something I just noticed recently. The white undertail coverts wrap up on the sides of the rump in flight. Again, it may just be just the males in display flight, but it almost appears as if there are short white outer tail feathers just at the base of the tail. There is a photo of this, here, on the American Bird Conservatory's "North With Spring" blog.

[Addendum, 4/20/2016: Bob Archer also recently posted about this display on his blog "Out and About Oregon Birds." It includes some neat photos of this display.]

Northern Rough-winged Swallow
Northern Rough-winged Swallow. Escondido, California. April 3, 2016. Greg Gillson.
These swallows nest typically in burrows they dig in sandy bank cuts on the edges of small streams. They don't nest in large colonies like the similar bank nesting Bank Swallows. However, Rough-winged Swallows have adapted to nesting in storm drains on the undersides of bridge overpasses. This likely accounts for the increase in numbers in San Diego in recent decades.

Three years ago I wrote an identification article on brown swallows for my now discontinued Pacific NW Birder blog.