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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