Re: [nfc-l] Nocturnal flight calls, Colorado's Front Range, 3+ years of data
Hi all, Andrew brings up an interesting question about midsummer nocturnal flight calls. As he suggests, I think there are a variety of different behaviors going on here. In the case of cuckoos, their midsummer nocturnal flight calls usually seem to be associated with good breeding habitat, suggesting that these are local breeders, not birds on the move. I know at least in New Jersey and Maryland where Black-billed Cuckoo is much scarcer than Yellow-billed, there are certain spots where I can go and listen at night and predictably hear Black-billed Cuckoo calling overhead. In the case of rails (King, Clapper, Virginia, Black, Sora, and Moorhen, at least, all give nocturnal flight calls in midsummer) my sense is that these are birds searching for ephemeral breeding habitats – maybe listening for frogs or other rails as they fly over. I could see Nelson's Sparrow or other marsh birds doing the same thing. Other non-marsh-birds may be doing the same sort of thing too. If a Grasshopper Sparrow’s field gets mowed, it needs to go find another one, and the safest time to do that would be at night. Then there is molt migration like the Chipping Sparrows in Colorado. Although relatively few species seem to do such a large-scale molt migration, a small percentage of many species do seem to move a moderate distance to molt while the bulk of the population stays to molt closer to the breeding grounds. Bobolink is a good example – small numbers regularly appear at coastal stopover sites from as early as late June before the large-scale migratory push appears in mid-late August. A number of warblers do the same thing, like the handful of Yellow-rumped Warblers that appear annually in Cape May in mid-August (and then vanish – lying low while they molt, I guess) before the rest of them arrive in October. best, Michael O’Brien - Original Message - From: "Andrew Farnsworth" To: "Ted Floyd" Cc: NFC-L@cornell.edu Sent: Thursday, July 29, 2010 8:36:27 AM Subject: Re: [nfc-l] Nocturnal flight calls, Colorado's Front Range, 3+ years of data Hello all, Ted, I congratulate you on another excellent and timely post. Regarding our attention to details: a couple of thoughts. . .apologies for hijacking the thread a little! Molt migration is a fascinating phenomenon, and many, myself included, are still eager to see a larger scale effort to monitor this behavior (in particular the nocturnal movements by acoustic monitoring). Has anyone on the list operated acoustic monitoring stations in the intermountain and mountain western US - Rockies/Great Basin/etc. - for any extended periods during the past few summers (or in the more distant past)? Ted (and others), what other species would you consider typical in the early July flights? And what of mid-June to early July flights in Colorado and elsewhere in the west? And expanding to a larger scale, what do we know about nocturnal movements associated with molt migration in other parts of the world (especially outside the western hemisphere!)? >From the US, East coast perspective, I am also interested to hear opinions about the nature of nocturnal movements that occur between mid-June and late-July in the Northeastern US. Presumably, in some cases, we are recording actual, continuous migratory movements for species that are late/early migrants (rails/Yellow Warbler, Louisiana Waterthrush) . . . but is this true in all cases? Are there species, such as those in the next sentences, for which we think we have a clear understanding of migration phenology but for which we really do not? Could be . . . but consider this . . . A number of mid-June to mid-July recordings made in New York state (various people in Ithaca and Manhattan at the least) have turned up an interesting diversity of nocturnal flight calls including Sora, Virginia Rail, Black-billed and Yellow-billed Cuckoo, Black-throated Blue Warbler, Canada Warbler, Grasshopper Sparrow, Nelson's Sparrow, etc. The placement of the recording stations and the attributes of the recordings are consistent with recording birds in nocturnal flight (rather than flight calls recorded nocturnally from birds on the ground or in typical habitat). Are we recording movements of adults of multi-brooded birds, failed breeders, pre-migratory movements of young of the year, facultative movements following irregular resources? Best, Andrew On Wed, Jul 28, 2010 at 5:00 AM, Ted Floyd wrote: > Hello, Birders. > > Here's an 86-kilobyte PowerPoint image, attached, summarizing the > results of my nighttime listening efforts at Greenlee Preserve, Boulder > County, Colorado, 2007-2010. Boulder County is northwest of Denver. The > county's western boundary is the Continental Divide, and the eastern > boundary is a bit higher than 5,000 feet. Data are July-November, > 2007-2009, plus July to date in 2010. >
Re: [nfc-l] Nocturnal flight calls, Colorado's Front Range, 3+ years of data
Hello all, Ted, I congratulate you on another excellent and timely post. Regarding our attention to details: a couple of thoughts. . .apologies for hijacking the thread a little! Molt migration is a fascinating phenomenon, and many, myself included, are still eager to see a larger scale effort to monitor this behavior (in particular the nocturnal movements by acoustic monitoring). Has anyone on the list operated acoustic monitoring stations in the intermountain and mountain western US - Rockies/Great Basin/etc. - for any extended periods during the past few summers (or in the more distant past)? Ted (and others), what other species would you consider typical in the early July flights? And what of mid-June to early July flights in Colorado and elsewhere in the west? And expanding to a larger scale, what do we know about nocturnal movements associated with molt migration in other parts of the world (especially outside the western hemisphere!)? >From the US, East coast perspective, I am also interested to hear opinions about the nature of nocturnal movements that occur between mid-June and late-July in the Northeastern US. Presumably, in some cases, we are recording actual, continuous migratory movements for species that are late/early migrants (rails/Yellow Warbler, Louisiana Waterthrush) . . . but is this true in all cases? Are there species, such as those in the next sentences, for which we think we have a clear understanding of migration phenology but for which we really do not? Could be . . . but consider this . . . A number of mid-June to mid-July recordings made in New York state (various people in Ithaca and Manhattan at the least) have turned up an interesting diversity of nocturnal flight calls including Sora, Virginia Rail, Black-billed and Yellow-billed Cuckoo, Black-throated Blue Warbler, Canada Warbler, Grasshopper Sparrow, Nelson's Sparrow, etc. The placement of the recording stations and the attributes of the recordings are consistent with recording birds in nocturnal flight (rather than flight calls recorded nocturnally from birds on the ground or in typical habitat). Are we recording movements of adults of multi-brooded birds, failed breeders, pre-migratory movements of young of the year, facultative movements following irregular resources? Best, Andrew On Wed, Jul 28, 2010 at 5:00 AM, Ted Floyd wrote: > Hello, Birders. > > Here's an 86-kilobyte PowerPoint image, attached, summarizing the > results of my nighttime listening efforts at Greenlee Preserve, Boulder > County, Colorado, 2007-2010. Boulder County is northwest of Denver. The > county's western boundary is the Continental Divide, and the eastern > boundary is a bit higher than 5,000 feet. Data are July-November, > 2007-2009, plus July to date in 2010. > > Before opening up the file, I suggest thinking for a moment about the > "East Coast bias" that practically all of us bring to the art and > science of listening to nocturnal flight calls. For me, having grown up > "Back East," the essence of nocturnal migration is a chilly night in > mid- to late September, the dark sky filled with the flight calls of > Swainson's and Gray-cheeked thrushes. > > But here in Colorado, you'll hear very little of that. Even though > Swainson's thrushes are common breeders in the Rocky Mountains, I hear > practically none of them flying over at night in mid- to late September. > And we get few if any of those other great "East Coast" birds flying > over at night in the fall: other "spot-breasted" thrushes, cuckoos, > Scarlet Tanagers, Rose-breasted Grosbeaks, and so forth. So you could > easily be excused for thinking there's not much to hear in the night > skies above Colorado. > > NOW check out the attached file. Certainly, there are night > flights--sometimes quite impressive--to be heard in Colorado's Front > Range region. But they're very different from the standard model, if you > will, from Back East. In Colorado, there's a steady trickle of bird > moving over by late July; the flight peaks by late August; and it's in > sharp decline by mid-September. The most frequently detected species is > the Chipping Sparrow, representing the bulk of the flight until the > first week of August; during the peak flight in late August, around 25% > of all detections are of Chipping Sparrows; and the species is pretty > much gone by late September. Certainly, that's not the impression you'd > get from an East Coast bias! > > (I've mentioned it before, but I'll say it again in case it's been > overlooked. Chipping Sparrows do not breed where I listen. These are > middle-of-the-night, no-nonsense molt-migrants flying from their > breeding grounds in the Rockies to molting grounds in eastern Colorado > and western Kansas.) > > Two thoughts, if I may, if you've actually made it this far: > > 1. Five years ago, NFC-L contributor Andrew Farnsworth had a great paper > in the Auk on "Flight calls and their value for future ornithological > studies and
