Details: Physiographic stratification and the BBS

Bird species distributions are closely associated with physiographic and vegetation features. In recognition of this, physiographic strata for the BBS were developed by modifying existing vegetation and soil distribution maps (Robbins et al. 1986). Maps of the physiographic strata have appeared in recent Annual Summaries and elsewhere (Droege and Sauer 1989, Butcher 1990). Because bird abundances differ among strata, most of our analyses of BBS data use physiographic strata within states or provinces (state-stratum units) as the smallest unit for estimating population trends or average relative abundance. Regional averages are constructed from state-stratum averages, weighting by land areas. This approach minimizes the influence of sampling bias associated with regional differences in sampling intensity.

  Strata names are: 

  1 Subtropical 
  2 Floridian 
  3 Coastal Flatwoods 
  4 Upper Coastal Plain 
  5 Mississippi Alluvial Plain 
  6 Coastal Prairies 
  7 South Texas Brushlands 
  8 East Texas Prairies 
  9 Glaciated Coastal Plain 
 10 Northern Piedmont 
 11 Southern Piedmont 
 12 Southern New England 
 13 Ridge and Valley 
 14 Highland Rim 
 15 Lexington Plain 
 16 Great Lakes Plain 
 17 Driftless Area 
 18 St. Lawrence River Plain 
 19 Ozark-Ouachita Plateau 
 20 Great Lakes Transition 
 21 Cumberland Plateau 
 22 Ohio Hills 
 23 Blue Ridge Mountains 
 24 Allegheny Plateau 
 25 Open Boreal Forest 
 26 Adirondack Mountains 
 27 Northern New England 
 28 N. Spruce-Hardwoods 
 29 Closed Boreal Forest 
 30 Aspen Parklands 
 31 Till Plains 
 32 Dissected Till Plains 
 33 Osage Plain-Cross Timbers 
 34 High Plains Border 
 35 Rolling Red Prairies 
 36 High Plains 
 37 Drift Prairie 
 38 Glaciated Missouri Plateau 
 39 Great Plains Roughlands 
 40 Black Prairie 
 53 Edward's Plateau 
 54 Rolling Red Plains 
 55 Staked Plains 
 56 Chihuahuan Desert 
 61 Black Hills 
 62 Southern Rockies 
 63 Fraser Plateau 
 64 Central Rockies 
 65 Dissected Rockies 
 66 Sierra Nevada 
 67 Cascade Mountains 
 68 Northern Rockies 
 80 Great Basin Deserts 
 81 Mexican Highlands 
 82 Sonoran Desert 
 83 Mojave Desert 
 84 Pinyon-Juniper Woodlands 
 85 Pitt-Klamath Plateau 
 86 Wyoming Basin 
 87 Intermountain Grasslands 
 88 Basin and Range 
 89 Columbia Plateau 
 90 S. California Grasslands 
 91 Central Valley 
 92 California Foothills 
 93 S. Pacific Rainforests 
 94 N. Pacific Rainforests 
 95 Los Angeles Ranges 
 96 S. Alaska Coast 
 98 Willamette Lowlands 
 99 Tundra.

Literature Cited

Butcher, G. S.  1990. Audubon Christmas Bird Counts. Pp. 5-13 in 
     J. R. Sauer and S. Droege, eds. Survey designs and statistical
     methods for the estimation of avian population trends. U.S.
     Fish Wildl. Serv. Biol. Rep. 90(1).

Droege, S., and J. R. Sauer  1989.  North American Breeding Bird
     Survey annual summary 1988. U. S. Fish. Wildl. Serv., 
     Biol. Rep. 89(13):1-16.

Robbins, C. S., D. Bystrak, and P. H. Geissler.  1986.  The
     breeding bird survey: its first fifteen years, 1965-1979.
     U.S. Fish Wildl. Serv. Resour. Publ. 157. 196pp.