An important graph, Ted, and it fits with my observation(s) that warblers
fill the trees mostly from Aug 25 to Sept 3.
Karl Stecher
Centennial
Ted Floyd writes:
>
>
>
> 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
>>
>
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