Hi folks. Just a bit of data to enliven the discussion. Tanner lists 169 separate records and/or locations of Ivory-bill sightings, from about 1811 to 1941. I hope to include in this document a histogram of those records. He lists 16 Louisiana records and three more from counties in W. Mississippi, mostly adjacent to Louisiana.* Of these 18 records, 12 are from NE or SE of Monroe (W. Carroll, E. Carroll, Madison Parishes), 4 from just west of Baton Rouge, and 2 from S. Louisiana (Avery Is. and Lafourche Parish [Stanley Clisby Arthur]). Lowery, unfortunately, mentions only the Tensas R./Singer tract birds and the 1971 "record".
Tanner says he did 37 months of field work, including all of the areas where Ivory-bills had been seen plus areas like the Pearl R. basin, from which there had been no records. He claims that there were no records of Ivory-bills occurring in any area after logging.
As I indicated earlier, he dismissed the Pearl R. Basin as being "completely cut over" when he visited it in 1938. Note, however, that the visit consisted of one August day...Similarly, he found the Atchafalaya basin "now completely cut over" and "found no good territory". In this case, Tanner worked the area for 5 days in July, 1938.
Ivory-bills were reported by Tanner as ranging over areas up to 3-4 miles across, with 1 to 1-1/2 miles more typical; winter territories were thought larger than summer. Birds flew across unsuitable habitat, on route, say, from a roost tree to nest tree, etc.
The are no records in Tanner between 1925 and 1929, and he comments that the species was considered extinct "for a few years after 1926".
All these data represent one pass through the report, hence some error bars.
*Bolivar Co, Sunflower Delta, Yazoo R. delta; one apparently on the Alabama side of the Pascagoula R.