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Thursday, May 2, 2013

Mystery barbs

Northern Rough-winged Swallow (Stelgidopteryx serripennis) 

When I first started working at the Bodega Marine Lab in 2005, I noticed this species nesting in an open pipe in the wall of a small outbuilding.  Amazingly, I think I've seen these swallows using the same pipe every year since!  I'm not sure if it's the same pair, or if it's been several generations of swallows.  (Some swallows have been known to live for 8-11 years, but a shorter lifespan is more typical.)

Note the brown coloration above, white below, and gray/brown wash across the breast and down the sides.

Although I've been familiar with this species for many years, I realized tonight that I didn't really know exactly why it was called a "rough-winged" swallow, so I did some research.

The outermost primary (wing feather) is unusual — there are stiffened barbs along the leading edge that make the margin of the wing file-like (the barbs are recurved in males).  Both the genus and species name refer to this character "Stelgidopteryx" means "scraper wing" and "serripennis" means "saw wing."  According to The Birds of North America account, "The possible adaptive significance of this feature remains a mystery."  (Although it goes on to mention that one possibility may be sound production during courtship or territoriality.)

I wondered if you could see the barbs, so checked a few photos that showed the leading edge of the wing.  The swallow is preening and scratching in the images below.

I couldn't see the barbs, but it was interesting to learn about them and to look for them.

I hope these beautiful swallows continue to nest locally for many more years to come!

1 comment:

Gay Bishop said...

Could the wings of the RWSW be used to excavate their nesting holes?
Gay bishop