01 March 2013

Friday Field Notes: A Bohemian Rhapsody

I see a little silhuetto of a bird,
It's got a crest! It's got a crest!
And a beautiful masked face!
... And waxy yellow tips on its wings?

I'll admit it: that was cheesy, at best. But the timing of this this naturalist-inspired Queen spoof is perhaps perfect. As winter crawls along, thousands of Bohemian Waxwings fill the valleys of western Montana with their sweet trill. Yet not every winter presents such a great opportunity to see them (indeed, their name "Bohemian" lends credence to their extremely nomadic nature), so it's worth taking advantage of the recent influx of these magnificent birds while they're here.

Bohemian Waxwings (Bombycilla garrulus) are one of three large passerine species that belong to family "Bombycillidae," commonly known as the Waxwings. The other two - Cedar Waxwings and Japanese Waxwings (native to Japan - surprised?) - are very similar in appearance to the Bohemian. Bohemian Waxwings (like their close cousins) inhabit temperate coniferous and mixed forests, and feed primarily on fleshy fruits and berries, though gleaning for insects becomes a primary summer feeding behavior. Interestingly, Bohemian Waxwings do not establish breeding territories, likely because the fruits they depend on are abundant during breeding season. As a result, these birds have no true songs, communicating almost entirely through their high-pitched trill.

While Cedar Waxwings are found in Montana year-round, Bohemians - outside of a small sliver in the northwestern-most corner of the state - only occur in winter. Thus, Bohemian Waxwings and Cedar Waxwings are both present in winter in Montana, and the two species frequently form mixed flocks. Hence, the problem: How does one tell apart these two extremely similar birds?

Cedar Waxwing top right; lower two birds are Bohemian Waxwings.
This photo, courtesy of the Cornell Lab of Ornithology, provides a big helping hand. The difference in size (Bohemian Waxwings on average are 2-3 centimeters longer and 1 ounce larger) is particularly noticeable, and other field marks become evident. Note the dark red coloration underneath the Bohemians' tails, which the Cedar Waxwing completely lacks. The best field mark to check for, however, is the belly color. Bohemian Waxwings have slate grey bellies, while Cedar Waxwings have vibrant, sulphur-yellow bellies that turn to amber nearer the head. Being able to pick up on this field mark will help you make a correct identification next time you're out and about with your binoculars.

Of course, you aren't very likely to get this good of a look at the two species side-by-side, as they are notorious for their constant gleaning and fluttering about. This is where being able to tell the difference in their call can be useful.  As you listen to the Bohemian Waxwing's high-pitched trill (http://www.allaboutbirds.org/guide/bohemian_waxwing/sounds), be sure to listen carefully, as you can hear each individual note in the call. Cedar Waxwings, by comparison, have a nasally, high-pitched whistle (http://www.allaboutbirds.org/guide/Cedar_Waxwing/sounds) which resembles more of a single "bzeeee" note. While at first the two calls sound very similar, you will quickly pick up on the subtle differences between the two.

Hopefully this crash course in waxwing identification helps you in your future birding pursuits. At the very least, you now know that Queen's "Bohemian Rhapsody" can be laughably re-mixed to accommodate birds and natural history topics!

Have you seen or heard any Bohemian Waxwings this winter? Be sure to let us know!

No comments:

Post a Comment