[birdky] Re: Weather and Birds -- Counterpoint (Beware ... VERY LONG ...)

Eddie Huber, Tom Becker, myself, and others can attest to what has been on the 
Ohio River around Louisville during the past few weeks ... a big NOTHING! 
Regular checks of the usual hot spots have revealed even less of interest than 
normal, which makes the remarkable occurrence of birds at Barren River Lake 
recently even more unusual. Likewise, there didn't seem to be an unusually high 
detection rate of similar "northwestern" vagrants in the region 10-14 days ago; 
if anything there seems to have been fewer than normal. So if weather systems 
brought the rarities to Barren River Lake, why not other places? I'm sure there 
have been at least a few other examples in the region lately, but there are 
rare birds scattered about everywhere all the time. Also, I noted on the TN 
listserv just yesterday that 2 California Gulls were reported at Pickwick Dam 
in southern TN over the weekend, although none were found in a search for gulls 
there the week before. Maybe it is just as likely that there is something going 
on with California Gulls rather than a particular weather system that has 
brought them to our region??? 

If one was to try to explain the occurrence of southern Indiana's recent Green 
Violetear, two Say's Phoebes in Kentucky in 15 days, and a White-faced Ibis in 
Henderson County all in recent weeks, I suspect that a bunch of assumptions 
would have to be made and at least several contradictory trails could be 
followed through the weather maps. It is easy to find a relatively reasonable 
explanation for the presence of a certain vagrant in our region based on the 
weather, but it may be just as likely to inaccurately attribute such an 
occurrence to the weather. Weather systems almost always progress across North 
America from west to east, but there are just as many eastern vagrants showing 
up in the west right now ... and most of them are eastern passerines that are 
bucking the same weather systems that one might be fooled into attributing the 
appearance of western vagrants in the east to.

This is not to say that weather systems don't greatly affect what birds we see 
in Kentucky and that they can have relatively predictable results. Waves of 
waterbirds, shorebirds, and warblers all appear throughout Kentucky during 
favorable migration conditions created by weather systems and they conversely 
may totally shut off during periods of unfavorable weather. The fun days are 
those when birds get fooled into thinking conditions along their path are great 
for migration, but they run into winds or precipitation moving in the opposite 
direction that result in massive fallouts. Extreme weather events such as the 
passing of tropical cyclones certainly explain the presence of some vagrants in 
a given region, but those are birds of very different habitats (coastal and 
especially pelagic) that are carried *totally* off course by remarkably large 
and extraordinarily strong wind fields into totally unfamiliar conditions for 
attempting to navigate. Beyond these well-known scenarios, I think there are 
many pitfalls in attempting to do too much analysis.

As a brief side bar, it should be noted that coastal species including Brown 
Pelican, Gull-billed Tern, Royal Tern, Sandwich Tern, and Black Skimmer have 
been found somewhat regularly in the inland central US *not* as the result of 
any known tropical system and that the report of a Sandwich Tern in Kentucky 5 
September 2008 was by no means certainly attributable to the passage of the 
remnants of Hurricane Gustav. That system was downgraded to a tropical 
depression while it was still in Louisiana, and most all vagrants deposited by 
it were found in Arkansas and Oklahoma. The only waif I recall in our region 
was a frigatebird (a species that sometimes gets flung inland great distances 
by such systems) in central Illinois ... actually the day *before* the main 
depression came through.

It is my belief that vagrants are around us all the time and it is more a 
factor of getting out and finding them than it is predicting their occurrence 
based on passing weather systems. For especially strong fliers like loons and 
gulls, vagrancy would seem to me to be more an issue of "choice" or "mis-wired 
internal navigation" than one being dictated by weather. Patterns of movements 
within species or groups of similar species -- and the changes and exceptions 
to these patterns over time -- can be quite interesting to follow. The easiest 
examples of such are irruptive winter finches like last winter's White-winged 
Crossbills. An environmental factor in the species' normal range (in that case 
a food deficiency) results in an abnormal movement. A less apparent one is 
Rufous Hummingbird; the pattern of occurrence for this bird in the southeast 
U.S. was a steady increase over the past 20 years until last year when for no 
explicable reason the pipeline shut off and all states in the southeast had 
many fewer and Kentucky had none for the first year in nine. During the past 
month to six weeks, Plegadis ibis of both species have been all over the 
region, perhaps the result of good breeding success, poor environmental 
conditions in their normal ranges, or some factor other than weather. The 
internet and state listservs now make keeping one's pulse on how these trends 
are unfolding each season much easier. Last winter it was quite fun to watch 
with great anticipation the southward progression of White-winged Crossbills on 
the listservs and then finally read that they had reached northern Kentucky!

As noted above, besides simply getting out and playing the admittedly very fun 
game of "find the vagrant," one can likely improve his or her chances of 
recognizing the possibilites by taking note of each species' or group's 
migratory periods and patterns. Most birds are remarkable navigators with 
abilities that we are only beginning to appreciate as banding and transmitter 
data accumulate. Moreover, vagrancy typically occurs within windows of time for 
a given species; that is, for example, most waterfowl move south from 
mid-October through early December, so one would most expect to find a vagrant 
of most waterfowl species during that period of movement. Although the recent 
Mew Gull at Barren River Lake is Kentucky's first, Indiana, for example, has 7 
records during fall, winter, and early spring including one on of all dates 
.... *18 October* 1997! So perhaps this is just the beginning of the period 
during which one might expect a wayward migratory Mew Gull -- a species that, 
by the way, happens to be relatively difficult to distinguish and may be 
largely overlooked (and thus under-reported) among our many thousands of 
Ring-billed Gulls??? -- to occur in our region based on the time of this 
species' migratory period. 

Something else that was very likely going on recently at Barren River Lake was 
the "Patagonia Rest Stop" effect ... when one rare bird is found, occurrence of 
birding increases there, resulting in more rarities being encountered. 
Certainly there have been numerous times over the past 20 years or so that 
folks have birded on the reservoir when weather conditions have been conducive 
to a fallout of vagrants from every region conceivable. David Roemer, himself, 
has likely birded Barren River Lake several hundred times over the years, but 
probably the three rarest birds ever to be found on the lake all occurred in a 
recent 10-day period. And had David not found the Pacific Loon -- at the time 
the rarest bird ever reported on the lake -- would he or anyone else have 
happened to bird the state park beach to find the Mew Gull a few days later? 

One final thought ... something that does appear to be significant regarding 
vagrancy is that certain locations seem to have a magnitism for rarities. These 
tend to be "oasis" type places (patches of green in deserts or lakes in areas 
where there are no others) that stand out from the surroundings. And even some 
of these seem to outperform others. For example, there is a sewage treatment 
plant Indiana birders refer to as Wakarusa in the northern part of the state 
that has hosted the following shorebirds in recent years: Mountain Plover (Aug 
2002), Sharp-tailed Sandpiper (Sept 2003), Curlew Sandpiper (22 May 2007), and 
Red-necked Stint (23 May 2007)... the stint was found by birders looking for 
the Curlew Sandpiper that had been found the day before ... can anyone say 
Patagonia Rest Stop?! To me that screams of inexplicable, just as the three 
rarest birds ever to be found on Barren River Lake occurring in 10 days in the 
latter half of October 2009 does. 

In summary, I think my perspective remains that you can certainly *sometimes* 
predict when there's a chance to find something like Sooty Terns or an Audubon 
Shearwater on Kentucky Lake, or even a good fallout of waterfowl on the state's 
reservoirs, but it is a crap shoot to try to figure out when a Long-billed 
Murrelet is going to be on the Ohio River at Louisville, or a Little Stint is 
going to appear on a relatively postage-stamp sized flood retention basin in 
southern Jefferson County. Sometimes I think we may be more accurate to say 
that it happened so simply because [a] god made it that way :o)

bpb, Louisville

________________________________

From: birdky-bounce@xxxxxxxxxxxxx on behalf of David Roemer
Sent: Sat 10/31/2009 9:58 PM
To: bird ky
Subject: [birdky] Weather and Birds



Those who are interested in the correlation between weather and the occurrence 
of vagrant birds may enjoy the information presented in the links below. 

The first shows weather maps beginning a few days previous to the arrival of 
the recent west coast birds at Barren Reservoir.  A series of high pressure 
systems across western Canada where these birds breed and migrate through moved 
east and southeast into the midwest.  Winds ahead of a high resulting from 
clockwise rotation can push birds off to the south and southeast.  Click on the 
Next Day link at the top right of the page to follow the progress of these 
systems.  A contributing factor was the rainy weather that was experienced in 
Kentucky at that time which often results in grounding migrants.  Scroll down 
to the bottom of each page for a precipitation map for that day.  With birds 
like this on Barren it would be interesting to know what dropped out along the 
Ohio River and Ky/Barkley lakes during that period.

Pacific Loon, Mew Gull and California Gull  13-19 October 2009
http://www.hpc.ncep.noaa.gov/dailywxmap/index_20091008.html

Also of possible interest regarding seabird vagrants are maps accessed by the 
links below which tracked hurricanes and tropical storms.  These are last 
plotted as they weaken and are downgraded from tropical depression status.  
These low pressure systems usually continue to travel to the north and east and 
can carry birds with them.  Below are some species which have occurred in 
Kentucky and maps of the weather systems associated with them.

Black-capped Petrels  4-5 October 1898
http://www.stormpulse.com/hurricane-seven-1898

Band-rumped Storm-Petrel  July 1994
http://www.stormpulse.com/tropical-storm-alberto-1994

Sooty Terns  4 October 2002
http://www.stormpulse.com/hurricane-lili-2002

Audubon's Shearwater, Sooty Terns, probable Brown Noddy  12 July 2005
http://www.stormpulse.com/hurricane-dennis-2005

Band-rumped Storm-Petrels 31 August 2005
http://www.stormpulse.com/hurricane-katrina-2005

Sandwich Tern  5 September 2008
http://www.stormpulse.com/hurricane-gustav-2008

David Roemer
Bowling Green




     
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