Hi, all. I hope the Veery and Swainson's Thrush flight Back East is great. Meanwhile, Bill Evans <wrev...@clarityconnect.com> writes:
> Incidentally, the most Wilson's Warbler flight calls that were > documented in any of the nights noted in the graph above was 31 > in nine hours of nocturnal flight call monitoring on Sep 4-5, 1992 > (post hurricane Andrew). That figure considers calls within one > minute of one another as a single call event and a theoretical > individual passing (there were 33 total WIWA calls that night). > Ted Floyd noted yesterday that he and his son heard WIWA flight > calls at a rate of 80/hr a few nights ago in Lafayette, CO. Such > a rate would be unprecedented in the east, though the timing of > the flight appears to be parallel. The good news for the typically > WIWA-starved folks in southern New Jersey is that if there were > ever a weather situation that would amplify your chances of recording > WIWA night flight calls, this is it and the next two nights should > deliver. To put things in perspective, Wilson's Warblers are abundant, to say the least, in the Front Range urban corridor of the Rockies, where I live, from late August to early September. If you know the species' daytime "chip note," you hear it frequently throughout the daytime hours, everywhere in the Front Range region. If you're actively birding for the better part of the day, you'll easily see and hear 50+ Wilson's Warblers--more than any other warbler species, and often more than all other warblers *combined*. I've seen more than 200 at a single migrant trap in the Front Range region. Wilson's Warblers at migrant traps a little ways to the east of the Rocky Mountains are about the closest we have to a parking-lot-at-Higbee-Beach phenomenon, here in Colorado. My point, if it's not already obvious, is that Wilson's Warbler is common as dirt here. (I assume most of our birds are pileolatas, with the bulk of "your" pusillas being to our east.) So although the heavy flights we hear in central Colorado would be "unprecedented" in the east, I think they make sense here. There's simply a huge volume of birds funnelling through a pretty narrow migratory corridor. For an East Coast analogy, think of Myrtle Warblers in the coastal thickets, or Ruby-crowned Kinglets flitting through the branches, or White-throated Sparrows calling back in the woods--that's Wilson's Warbler for you in our region. I mean, our Brewer's Sparrow flights would be unprecedented in the East, too... ;) Two other things: 1. Bill notes the timing of the fall flights of Wilson's Warblers are parallel for the Eastern and Mountain time zones. That would appear to be the case, but I wouldn't read too much into it, given that we are dealing with different subspecies. Consider the differences in the timing of the flights of eastern vs. western Chipping Sparrows; the heaviest Chipping Sparrow (subspecies arizonae) flight this year for me here in Colorado was the night of July 30-31, whereas I imagine listeners/recorders in the East have yet to hear the heaviest Chipping Sparrow (subspecies passerina) flight of the year. Or consider the differences in the timing of the flights of eastern vs. western Orange-crowned Warblers. Orange-crowns (subspecies orestera) are very much on the move here by late August, but credible reports at mid-latitudes in the East (subspecies celata) are quite uncommon until around Sept. 20th. 2. With just a moment's reflection, you can tell that Bill is using a more conservative reporting standard than I am. Indeed, Bill's conservative standard would give an absolute maximum of 60 flight calls per hour. For my purposes and interests, the total number of flight calls detected per unit time works best; but I accept that Bill's standard might be better in other applications. Oh, and just to open up a can of worms, I note that *any* measure of detection is just a proxy--almost unquestionably with certain statistical biases--for the "true" population. Is calling intensity density-dependent, for example? If so, and I think that's a distinct possibility, then the whole question of heavy vs. light flights is subtly circular. Best, Ted ------------------------------- 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/ --
