Let the quibble battle begin... 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:
<https://lh5.googleusercontent.com/-n9XnLoe1kDo/VA8ocfu0mEI/AAAAAAAAAAU/5Uqg4l-nhCQ/s1600/birds.jpg> 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. http://ebird.org/ebird/GuideMe?cmd=decisionPage&getLocations=states&states=US-CO&bYear=1900&eYear=2014&bMonth=9&eMonth=9&reportType=location&parentState=US-CO 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 *spizella*s 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. Bryan Bryan Guarente Instructional Designer/Meteorologist UCAR/The COMET Program Boulder, CO On Tue, Sep 9, 2014 at 10:27 AM, Ted Floyd <[email protected]> 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: > > > <https://lh5.googleusercontent.com/-n9XnLoe1kDo/VA8ocfu0mEI/AAAAAAAAAAU/5Uqg4l-nhCQ/s1600/birds.jpg> > > 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 Floyd > > Lafayette, 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)* >> [image: Inline image 1] >> >> *Thursday 12am (forecast model)* >> [image: Inline image 2] >> >> 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 Guarente >> Instructional Designer/Meteorologist >> UCAR/The COMET Program >> Boulder, CO >> > -- > You received this message because you are subscribed to the Google Groups > "Colorado Birds" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/cobirds/556586d7-476e-45b5-9790-4c6c3ef627ff%40googlegroups.com > <https://groups.google.com/d/msgid/cobirds/556586d7-476e-45b5-9790-4c6c3ef627ff%40googlegroups.com?utm_medium=email&utm_source=footer> > . > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "Colorado Birds" group. 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