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A Natural History Lexicon: Rictal Bristle

Welcome to Wingtrip’s Natural History Lexicon, a regular rundown of natural history terms. To find future and past posts on this subject, simply search “natural history lexicon” or find it in the tags. Thanks for reading!

Rictal Bristle

\ˈrik-təl\  \ˈbri-səl\

– Highly specialized feathers found around a bird’s face and bill, that are both stiff and lack barbs on their outermost length.

As I walked outside today, my ear caught the monotonous pipping of a Olive-side Flycatcher, topping a Douglas fir towering overhead. This was a slight surprise; our resident San Juan Islands breeders have long been silent, and absent. My assumption was that this bird was moving through from further North, bound for Mexico and beyond. Migration is afoot and the meadows and forests of the San Juans have been alive with the sounds of birds heading for better pasture. Many of these birds are insectivorous, leaving for places with winter supply. This is what brought me to the term “rictal bristle” (not be confused with rectal bristles, which are embarrassing and no one wants to talk about).

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An example of rictal bristles on a flycatcher being banded by scientists in Central Oregon.

Many birds have bristle like feathers serving a variety of functions, but all hold the same profile of simple, hair-like feathers consisting of a mostly bare rachis (the shaft) and sometimes basic plumes near the base. Most insectivorous birds have rictal bristles around their mouth and it’s widely been assumed these help them scoop up insects more effectively. Because they are stiff, bristles are also thought to be protective, positioned around the delicate eyes and nostrils (think of those wriggling, potentially dangerous insect prey). They also may provide tactile sense (there’s debate of their purpose only because it’s so hard to see these feathers in action). Most evident on insectivorous birds that catch their prey on the wing, they also seem to aid birds leading nocturnal lives. Nightjars (both insectivorous and nocturnal) are the prime example. You really begin to appreciate their placement when you hold a bird such as a flycatcher above in the hand.

As I realize yet again that every season is simply too short, for the human mind and the temperate world’s denizens, I can’t help but pine for the autumnal loss of swallows, nighthawks, flycatchers, and vireos that will be gone for months on end. Thankfully seabirds will soon flood from the North and the permanent residents continue their lives nearby. Before I have time to realize they’ve been gone too long, I’ll step outside in the spring and find myself again listening to the insistence of a Olive-sided Flycatcher.

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