On Tuesday, September 9, 2014 11:35:23 AM UTC-6, Bryan Guarente wrote:
Let the quibble battle begin...
Actually, I don't have all that much quibbling left in me!
And I strongly concur with Bryan Guarente's basic caution about what we detect vs. what's really out there.
In recent years, birders in Pennsylvania have learned that there's far more mid-summer nocturnal migration than had been previously appreciated. The reason the phenomenon went so unnoticed for so long is twofold. First, those danged insects! Nights in Pennsylvania in mid-summer are maddeningly loud with katydids, crickets, grasshoppers, cicadas, and even the drone of munching caterpillars; it's so hard to notice little flight calls over that racket. By late September, though, when the nights are cooler, the birds louder (thrushes, etc., coming in), and the insects a fair bit quieter, it's much easier to hear the birds. The second reason is psychological: If birders Back East "know" there are no birds to be heard migrating in July, then they won't hear them. Believing is seeing (or hearing).
Bryan has emphasized the physical factors that determine detectability, and I sure agree. I think the psychological factors are important, too. I mean, who would go out to listen at night in Colorado in mid-July to listen for migrating Chipping Sparrows--unless you knew they were up there. Or here's one: Now that we know there are Baird's Sparrows in Colorado in late August to early September, we're all of a sudden seeing them, in droves. (My suspicion, by the way, is that they're migrants, and that they've always been here--just look at the breeding and wintering ranges--but we were just looking at the wrong time of year. However, I would be delighted for folks to confirm breeding in 2015 and beyond.)
Once again: Believing is seeing.
As to eBird, I'm a huge fan and chronic user, but it's important to acknowledge the self-fulfilling prophecy bias in the eBird database. We tend to go birding where we "know" there are lots of birds. Not all that long ago we didn't know stuff like: Go to the mountains in October and even November for seabirds; check "Mallard" flocks for Mexican Ducks; Sprague's Pipits are perfectly regular on migration in eastern Colorado; Hepatic Tanagers like tall pinyon pines on north canyon walls; Lucy's Warblers breed in Montezuma County; and, of course, the night skies over eastern Colorado light up in July and August with migrating Chipping Sparrows. Now we know that stuff, and eBird is lighting up with swans in the Mountains, Lucy's in Yellow Jacket Canyon and Sprague's Pipits at the Fox Ranch, Hepatic Tanagers in the Purgatoire drainage; Chipping Sparrows at night in July, and Mexican Ducks practically year-round.
That's great stuff, and the documentation of it all is a tribute to Colorado birders' willingness to think outside the box--to explore new places, to go out at the "wrong" time of the year, and, at all times, to question the conventional wisdom.
Ted Floyd
Lafayette, Boulder County Colorado
Ted said, "But I think it's still the case that the peak volume of individuals is in late August. Here's a graph that portrays that result:
The top curve (blue) is flight calls per hour (all flight calls) over Lafayette, Boulder County, 2007-2009, 25-day floating average; the bottom curve (pink) is Chipping Sparrows only. As you can see, there's a peak in late August and the very beginning of September, and then a pretty serious drop-off."One of the problems we are battling against that is a difference between "back East" birding and "Old West" birding is that the weather for night detection is significantly different. With the dewpoints in the East being significantly higher for most of the year than Colorado, the cloud cover is lower in the East than in the West skewing your dataset to the time when we have the most moisture in the atmosphere here in Colorado during fall migration (Monsoon season). We have mid-level moisture from the Southwest monsoon and also moisture from the Gulf of Mexico with easterly winds. Since this is typically at the end of the meteorological summer here in Colorado, I think most of this dataset is reflective of night flight call detection and NOT actual detections during the day and crossing that data with the moisture/cloud cover.If you look through the eBird barcharts for the entirety of Colorado during September, you will note that there are still a bunch of passerines that "peak" (have the greatest number of detections on eBird) in weeks to come not weeks past.In re-examining the eBird bar charts I am actually seeing a bunch of birds that are peaking this week that I wasn't paying attention to last night, so I believe that there may be more passerine migration than mentioned before and thank you Ted for making me look at this again.As to another point, Chipping Sparrows are likely participating in a molt migration or dispersal and maybe not a full fledged migration (arguable I know). Looking at eBird data though, not just night detections at your site (great dataset by the way), we find that Chipping Sparrows are actually peaking in the first three weeks of September. Is that data real? Well the short answer is... kinda. We are aggregating across the entire state, and mostly we are dependent on diurnal viewing, eBird reporters, who "think" it is a Chipping Sparrow in the time of year when spizella species are very hard to tell apart if not impossible depending on age. I have been catching myself not looking at spizellas recently because I don't want to fight that battle. So lots of layers to the argument. So since that is more of a local migration, it is problematic to use a weather argument for Chipping Sparrow migration aside from locally. If we use something from farther away, like American Tree Sparrow, we get a different picture of weather relating to bird migration.As my data point for the upcoming weather, I went to McIntosh Reservoir today in NW Longmont, and found only 11 gulls on the entire lake. No grebes, and no shorebird habitat in sight (sigh). I'll see if I can get there on Thursday for a repeat data point.Thanks for "arguing" Ted.BryanBryan GuarenteInstructional Designer/MeteorologistUCAR/The COMET ProgramBoulder, COOn Tue, Sep 9, 2014 at 10:27 AM, Ted Floyd <tedfl...@hotmail.com> wrote:--
Outstanding post by Bryan Guarente. I nominate it for Best-COBirds-Post-of-the-Year award!I also wish to quibble with just one point from Bryan's excellent post:Short read: Get out Wednesday night/Thursday morning when it starts to cloud up overnight for night migrants. If you don't night listen (who the heck would do such a thing...), get out there in the intermittent drizzle/rain in the morning and get your feet wet with migrants. Check for shorebirds, gulls, terns, and jaegers. Passerine migration isn't in the big swing yet, so expect some of the early ones, but nothing major in terms of numbers.That part in bold red (my doing) is definitely the convention wisdom Back East, in, say, Pennsylvania, where both Bryan and I grew up. Basically, wait till after Labor Day weekend for the big passerine flights. Here in the Interior West, though, we've learned that the heavy flights are earlier. Of course, there's good stuff still to be found well into the fall. And among the most wondrous of our annual migration phenomena are the night flights of American Tree Sparrows in early November. But I think it's still the case that the peak volume of individuals is in late August. Here's a graph that portrays that result:
The top curve (blue) is flight calls per hour (all flight calls) over Lafayette, Boulder County, 2007-2009, 25-day floating average; the bottom curve (pink) is Chipping Sparrows only. As you can see, there's a peak in late August and the very beginning of September, and then a pretty serious drop-off.(If you're curious, you can read more in this article in Colorado Birds-- Floyd, T. 2011. Mid-summer dispersal, nocturnal movements, and molt migration of Chipping Sparrows in Colorado: Taxonomic implications and conservation applications. Colorado Birds 45:180-196.)For sure, I'll be out on Thursday morning, and I appreciate Bryan's heads-up.Oh, and I hasten to point out that we certainly can get good strong passerine flights in Colorado even well after Labor Day. One of the best I ever encountered was the morning of 29 September 2008, when birds were going over at a sustained rate of 200 flight calls per hour.Ted FloydLafayette, Boulder County, Colorado
On Monday, September 8, 2014 9:29:19 PM UTC-6, Bryan Guarente wrote:COBirders,You may have heard we are in for a bit of a stumble into fall weather this week. It still looks to be true. However, fall weather means there are birds on the move as well, so shooting the messenger before you get your forecast could mean you don't get your next forecast.Short read: Get out Wednesday night/Thursday morning when it starts to cloud up overnight for night migrants. If you don't night listen (who the heck would do such a thing...), get out there in the intermittent drizzle/rain in the morning and get your feet wet with migrants. Check for shorebirds, gulls, terns, and jaegers. Passerine migration isn't in the big swing yet, so expect some of the early ones, but nothing major in terms of numbers.Long read: The winds look nice for high Arctic movement toward the central US. Get out Wednesday night to listen for nocturnal migrants as the cloud cover develops and lowers throughout the night. Best night flight possibilities are likely in the early morning hours of Thursday at approximately 4am.Following maps are streamlines of winds showing you the major push of winds from the high arctic.Wednesday 6pm (forecast model)Thursday 12am (forecast model)We (Colorado) will be on the western edge of the frontal passage giving us a slight turn in the winds toward the mountains with the passage. I would suggest there will be plenty of nice birds out there on Wednesday and especially Thursday. I fully expect to hear reports of Horned Grebes, Sabine's Gulls, Common/Arctic Terns, Buff-breasted Sandpipers (more), Black-bellied Plovers (more), American Golden-Plovers, gobs of peeps, Pectoral Sandpipers, Short-billed Dowitchers, Long-tailed Jaeger (more), first Merlin's of the season, another push of Wilson's Warblers, and the first White-throated Sparrows. These are just the obvious ones to me (and the rare ones that will likely get more attention from the list).The drizzle/rain will make the situation a little murkier, but the best birders go birding in inclement weather and pay dividends for it. This won't even be that inclement. Expect the high on Thursday to be in the upper 50s/lower 60s on the plains and foothills and temps should be colder in the mountains. Don't be fooled if the winds are out of the southeast on Thursday. It is a good thing.Thanks for listening. Report any and all fun things to COBirds so I can check my work later and we can come to understand weather and migration better. If you have any further questions, let me know and we can discuss it further privately or let the list know and we can discuss this openly. I am open for either.Bryan GuarenteInstructional Designer/MeteorologistUCAR/The COMET ProgramBoulder, CO
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