how to detect ruffled feathers

In my book review of The Songs of Insects, I enthused over the fantastic photography of Wil Hershberger. Browsing through his website, I found a page where he notes the presence of two small filoplumes on the napes of songbirds he'd photographed. Filoplumes are specialized feathers, long and hairlike, that are most numerous at the base of wing feathers. Special sensory cells at the base of filoplumes transmit information on the position and movement of wing feathers during flight. According to the Manual of Ornithology: Avian Structure and Function, many passerines also have filoplumes sticking out of their crown and nape, "perhaps warning the bird when wind disrupts the smooth outer surface of the plumage."

I found this incredibly intriguing, and when I had the time, I looked for these plumes on the birds I banded this spring. Sure enough, there they were!  I was able to find them on a variety of species, both male and female, and could even see them on some older head shots I had taken during previous fall banding seasons. Although not particularly easy to photograph (especially with one hand!), here is a little slide show of some of my shots. Look at the back of the neck -- you might have to slow the speed down a bit or pause on some photos. (Note: apparently some Firefox users cannot see the Flickr slide show, a known bug with Flickr. If you have a Flickr account, it might help to log in.)

Species in order: Yellow Warbler (male then female), Orchard Oriole, Black-and-white Warbler, Brown Thrasher, White-throated Sparrow, Tennessee Warbler, Magnolia Warbler, Rose-breasted Grosbeak (male then female), Black-thr Green Warbler, Connecticut Warbler, Golden-winged Warbler, Nashville Warbler, Purple Finch, Wilson's Warbler, Baltimore Oriole, Common Yellowthroat. Created with Paul's flickrSLiDR.

A 1989 paper (pdf) in the Condor, the journal of the Cooper Ornithological Society, described the presence of these protruding filoplumes on the napes of many passerine species. The authors noted that species which lacked these plumes had dense, stiff feathering on their napes, while species that displayed the filoplumes had softer and more flexible feathering in this area. They also concluded that these plumes served to detect disturbances in the feathers in an area that birds could neither see nor reach. The looser plumage might have less insulative properties to begin with, and unnoticed disheveled plumage might make a bird even more vulnerable to heat loss. A quick shake or perhaps scratch of the head, or facing into the wind can smooth the feathers once again, correcting the situation.

It's hard to believe I handled tens of thousands of birds -- with part of the routine being close scrutiny of plumage -- without making particular note of this interesting characteristic!

Comments

[John]

The slide show is giving me the message "No such photos found!"

[Mike McDowell]

Very cool. I've seen this in some of my photographs, too. I didn't know what they were for, though. Great info!

Mike M.

[Jochen]

That's a very interesting post!

Even though I can see the slides, the slide show is giving me the message I should start banding and get this close to so many great species. I mean, Nuthatch, please: Golden-winged Warbler, you've got to be kidding! Took you long with photoshop?

[Nuthatch]

People usually get more worked up over the Connecticut Warblers I band, but I've actually banded three times fewer Golden-winged Warblers than Connecticuts. I sense you may have to pay me a visit this fall...

[Patrick]

A little hairspray usually does the trick to keep those "flyaways" down... :)

This was a really interesting post about something I'd heard of, but didn't know much about. Great pics too!

[Jochen]

Yes, you sense right but I probably will be back in Germany by the time fall migration sets in. That's very unfortunate!
But one of these days... and there's no escaping that ... I may have to pay you a visit!