Hello, All. (Nice night flight in the 1am hour this morning, Friday, Sept. 3, over Lafayette, Boulder County, Colorado. First good push of presumed Orange-crowned Warblers, which migrate much earlier in fall in Colorado than in, say, Ithaca, New York. Wilson's Warblers continuing, too, and Chipping Sparrows--presumably mostly juveniles now. Anyhow...)
=============================== As I think a lot of us know, Barn Swallows give an amazing variety of vocalizations while on the wing. They can sound like Solitary Sandpipers, they can sound like Scarlet Tanagers, they can sound like House Finches, they can sound like Lark Buntings, they can sound like Bullock's Orioles, and on and on and on. At least here in Colorado, Barn Swallows fly by night and are exceedingly vocal. Unquestionably, I hear far more Barn Swallows by night in Colorado than any other bird species, from mid-July into early September. These are birds high overhead, calling almost constantly. In mid-July, I assume these are mainly or entirely local birds just socializing at night. The Barn Swallow just happens to be an especially active night-calling passerine. (Other passerines that are vocal by night on the breeding grounds in Colorado include Cordilleran Flycatcher, Violet-green Swallow, Sage Thrasher, Yellow-breasted Chat, and Cassin's Sparrow.) Broadly speaking, then, the following statement from the Evans & O'Brien CD-ROM needs to be updated: "Primarily a diurnal migrant. May migrate at night in spring in the Gulf of Mexico region. Flight calls are given regularly by perched and flying birds during the day. Not known to give flight calls at night." Again, and just to beat a dead horse, I hear more nocturnal flight calls from Barn Swallows than from any other bird species. But what about the more nuanced question of Barn Swallows on active nocturnal migration? First, do they migrate by night? And, second, if so, what do they sound like? Well, I've been wondering about that a fair bit. Given that Barn Swallows are flying around at night anyhow, often quite high up, and well away from roosts and nest sites (e.g., high above lakes and pine forests), mightn't they also be nocturnal migrants? So here's my hypothesis. The flight call given by Barn Swallows on active nocturnal migration seems to be what Evans and O'Brien call the "vwit" call. That is the call I hear from birds that I judge to be moving north to south on nights when other expected species are on nocturnal migration. It's a rising flight call, with 3 or more "bands." If you have the Evans and O'Brien CD-ROM, it's this one: Flight Calls\SPECIES\SWALLOWS\BARS\BASWVAR.HTM The problem is, Barn Swallows make me nervous, ID-wise. Is the Barn Swallow's "vwit" call distinguishable from the flight calls of Bobolink (presumably a rare migrant where I listen), Bullock's Oriole (common migrant here, but most movement appears to be diurnal), Lark Bunting (distinctive flight call, but, I swear, some sound like Barn Swallows!) or even House Finch (notoriously variable, and who's to say they don't move at night?). I'm not so sure. But here's what I can say: Barn Swallows are extremely vocal, on the wing, at night, at least in Colorado, and that's a broad pattern, something I've noticed all across the region; their "vwit" call is certainly one I hear a lot of; and it seems to be the call of birds on active nocturnal migration; but we need to be aware of (at least, I need to be aware of!) the possibility of confusion with other birds with rising, multi-banded, fairly-low-frequency flight calls. In other words, next time you think you're hearing orioles or Bobolinks or Lark Buntings or something, be aware of the possibility of Barn Swallows, certainly on the wing by night, and quite possibly in the act of active nocturnal migration. ------------------------------- Ted Floyd Editor, Birding Follow Birding magazine on Twitter: http://twitter.com/BirdingMagazine ------------------------------- -- NFC-L List Info: http://www.NortheastBirding.com/NFC_WELCOME http://www.NortheastBirding.com/NFC_RULES ARCHIVES: 1) http://www.mail-archive.com/nfc-l@cornell.edu/maillist.html 2) http://birdingonthe.net/mailinglists/NFCL.html 3) http://www.surfbirds.com/birdingmail/Group/NFC-L Please submit your observations to eBird: http://ebird.org/content/ebird/ --
