[TN-Bird] Re: more on those cumberland county henslow's sparrows; and some bbs ruminations
- From: Bill Pulliam <bb551@xxxxxxxxxxxxx>
- To: TN-Bird <tn-bird@xxxxxxxxxxxxx>
- Date: Mon, 17 Jul 2006 17:44:09 -0500
Speaking as someone who just this summer turned up one of those
small, previously undocumented populations, my experience may be
relevent to the quest for better information:
I did not just happen to stumble across the birds. I read on TN-
birds and on the Henslow's Sparrow Atlas project page about the known
distribution and the detailed habitat requirements, and I thought
long and hard about where there might be patches of this habitat in
Lewis County. Once I came up with what seemed to be the best bet
(The Farm's large unmowed fields), it fortuitously happened that I
was going to be going there in a few days to help Cynthia Rohrbach
with point counts. I made a point of being especially alert for that
easily-overlooked song when we walked along the best habitat, and
sure enough, we found one. Later visits by other observers found at
least three.
I think this semi-systematic approach is the best bet:
(1) learn the habitat
(2) study maps, drive backroads, search your recollections to find
this habitat in the area
(3) go there and listen listen listen.
The recently-known distribution suggests there could be be Henslow's
Sparrows in any suitable field ANYWHERE in Middle Tennessee, as there
are records this summer alone from the West Highland Rim, East
Highland Rim, Central Basin, and Cumberland Plateau. Some of the
West Highland Rim counties are pretty short on barrens habitat
(Perry, Hickman, Wayne come to mind) but who's to say they aren't
also going to be found in fields in the larger bottomlands on the
Duck, Buffalo, etc.? And no rason to rule out East and West
Tennessee. Many recent records are outside the "historical range;"
regardless of whether this is from range expansion or better observer
knowledge, it means that we should be alert to the possibility from
border to border, not just near places they have already been found.
The BBS/Henslow's Sparrow issue is a general problem with BBS and
other point-count-based surveys. They do not adequately sample birds
with clumpy distributions. We often think of herons and such in this
regard, but it also includes birds like Henslow's Sparrow, Willow
Flycatcher, and Dickcissel in the areas where they are less common.
At The Farm, the Henslow's Sparrow colony (if three birds do a colony
make) fell between point counts on the transect; had we been driving
instead of walking between the points we would have missed them.
These sorts of birds are best found by targeted searches of clumps of
suitable habitat. Unfortunately, this isn't generally going to
happen until we are first alerted to their possible presence by a few
chance encounters, so these birds can remain unnoticed for decades.
Back when I was working the South Carolina Breeding Bird Atlas, one
of the many surprises was the widespread presence of "Piedmont"
warblers (Ovenbird, Worm-eating, Black-and-white, etc.) in small
bottomland hardwood patches amongst the pine flatwoods of the Lower
Coastal Plain. After I stumbled on a few, and began more targeted
searching, they turned up in nearly every block I covered in that area.
Bill Pulliam
Hohenwald TN
http://bbill.blogspot.com
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