Kenn Kaufman <[log in to unmask]> wrote:      at Metzger Marsh ... I came up with a conservative count of
about 1320 Gadwalls, outnumbering all the other ducks combined.
  These are far higher numbers than what have been published in the past ...

  ------------------

  Within the context of readily available information on Ohio's birdlife,
  Kenn's remarks are perfectly correct. What is imperfect, however,
  is the presentation of the ornithological record in Ohio. No more so
  than anywhere else I am sure. Indeed, I think Ohio has been (and is)
  served by some very fine editors of that record, and as a consequence
  has among the more comprehensive and current sets of publications
  for every level of birdwatcher.

  But I think the point needs be made that time and space constraints,
  coupled with an
  ever growing mound of data, inevitably bring to the fore sampling bias.
  Not only that of the observer, which is often cited, but that of the editor
  as well; something all too frequently overlooked, or understated.

  I know I have mine, and the most difficult aspect of writing a seasonal
  review such as for North American Birds, is that requiring cutting 50
  or more records from my original draft so as to make the word limit.
  And what of the 12 - 32,000 records that did not make my first
  cut?

  Recently, in an article for The Ohio Cardinal, Bill Whan noted
  the apparent oversight, on the part of Peterjohn, of a good many
  specimen records with regard to his 2001 overview of Ohio
  avifauna. Given the herculean task of uncovering these records
  to date (for which we have Robert Foppe to thank), I can see
  why.

   And so I come to what we think we know about migrant Gadwall
  concentrations in Ohio as I it is instructional as to the process
  of getting a report into the record.

  Peterjohn's review of the state's avifauna in 2001, being the most recent
  and in depth, especially as regards migrant concentrations, is our starting
  point. We learn in the opening paragraph that Gadwalls have been on
  a comeback for several decades right up to the point of publication.
  At that point (late 1990s), we learn that upwards of 700+ may be found
  in the marshes of the Western Basin in spring. This is what may be SEEN
  by birders on the ground. But it does not really speak to what may be
  present, given the host of biases in the observer sample. Therefore
  Peterjohn supplies us with some representative aerial counts, albeit
  from the fall period only. Or are they representative? The figures, of 12 &
  19,000 in Nov of 1994 & 1996 respectively, are cited from Harlan (1994)
  and Fazio (1997) seasonal reviews in The Ohio Cardinal. We in turn
  were citing the Ohio Division of Wildlife. But such information was not
  always available in time to make our deadlines. Comparatively few
  years of aerial data have been cited in the broader ornithological record.

    Within reach of my desk, just now I pulled out two sets of aerial
  surveys that probably are not widely cited. Here are some figures
  updating Peterjohn.

  In Spring:

  Some 4967 Gadwall for 31 March 1999, included

  1475 at Magee Marsh, 780 at Navarre Marsh, and 500 at
  Pickerel Creek

  Of 6900+ Gadwall for 2 April 2001, counts included

  1980 at Magee Marsh, 1245 on Sandusky Bay, and
  630 for Killbuck Marsh (incidentally about double the
  published maximum spring total inland for a single property)*.

  *aside from bragging rights, such things matter a good
  deal to the Audubon Ohio IBA program.

  In the years since, no doubt much more can be gleaned
  from published and unpublished works. This is just a
  quick sampling (with its own bias ... namely the length
  of my arm and the time I wish to dedicate to this email).

  Questions/issues remain. The aerial surveys are now twice
  monthly ... a refinement from the 1990's. Gadwall, based
  on ground counts over the decades, peak in spring
  consistently the first week in April. Aerial counts don't
  get off the ground until mid-morning, likely missing
  birds that move out to surrounding farm fields at sunrise
  (albeit more an issue with swans and geese). How often
  are aerial surveys conducted after 31 March? As an editor,
  I am rarely privy to information after March (the April date
  above being the exception). Therefore, do we really have
  a good handle (in the literature) on the abundance of
  Gadwall in Ohio in spring?

  Arguably not ... read my PS at the end.

  And what of ground counts. With regard to Peterjohn's
  citation of aerial counts, he offers "such numbers are
  not apparent from the ground". Indeed, one comparison
  supports this view. Consider that the aerial view of
  Ottawa N.W.R. (main unit only) on 2 Nov 2000 counted
  1675 birds while on the 5th, the monthly Ottawa N.W.R.
  census with Ed Pierce leading 9 observers canvassing
  the property tallied 500. As it happens, I counted the
  Gadwall present on the estuary and the immediately
  adjacent moist soil unit of Ottawa N.W.R. 8 Nov and
  came up with 1170 (see Ohio Birds & Natural History
  2(2): 61.).

  I don't think ground counts need be so lop-sided. I
  generally avoid census work where I don't think what is
  visible is a good representation of what is present. For
  the Lake Erie marshes, this can be daunting, even given
  my penchant for standing atop my Ford Explorer to
  scope above the Phragmites. No, I find ground counts
  in this region, and occasionally elsewhere in Ohio, are
  best served by waiting for the now ubiquitous eagle
  to come along and flush all the waterfowl. It has served
  me well. When you have an idle moment, look up my
  waterfowl numbers for 17 March 1997 (a day long survey
  of the Lake Erie marshes) within The Ohio Cardinal, then
  compare these (in particular Ring-necked Duck and
  American Wigeon) with the aerial surveys from 21 March.
  You might be surprised.

  cheers

  Vic Fazio
  Shaker Hts, OH
  PS> In Trautman's 2006 publication (R. Stuckey Ed.) on the
  birds of Western Lake Erie, we learn that his 4 April 1964
  survey of Ottawa County netted him 2000 Gadwall.

  Had we but known before.






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