Data are recorded by Atlas "blocks", which are identified by USGS 7.5 minute
topographic maps and named by the topo sheet (as Quad Name on reports) and block number. A
block is 1/6 of a topo sheer and numbered from the northwest corner (1) to the southeast
corner (6). A block is 2.5 minutes of latitude by 3.75 minutes of longitude. The area of a
block is approximately 10 square miles.
Evidence of birds nesting within an Atlas block was recorded with a set of codes that
describe behavior and physical evidence of nesting. These codes are divided into four
hierarchical categories, three of which indicate breeding. "Observed," "Possible,"
"Probable," and "Confirmed" breeding codes represent increasing evidence that nesting
occurred within the block a species was recorded. "Probable" and "Confirmed" categories
were further segregated into hierarchical codes that represent individual breeding behaviors
or physical evidence of nesting. A description of breeding codes may be provided upon
All of Pennsylvania's 4,928 atlas "blocks" were surveyed, with an average of 65 species per
block recorded. A total of 188 breeding species were documented statewide. Data catalogued
geographically by atlas "block," USGS 7.5 minute quadrangle, county, and physiographic
province. Species files include political status designation and a number of life-history
Note: When the Breeding Bird Atlas Database is downloaded from the PASDA website, the links
which connect the supporting dBase files to the ArcView shapefile will be lost. In order to
use the Atlas, you must first re-establish the links in your ArcView project. Bba.dbf is
linked to Bbadat.dbf and Bbaocc.dbf via "BLOCK_ID". Bbaname.dbf is linked to Bbadat.dbf via
Disk Contents: Bba. *** - Three files (.shp, .shx, .dbf) that form the necessary components
of an ArcView GIS shapefile format. This is the GIS layer of the Breeding Bird Atlas sample
grid. The 4928 Atlas blocks represent each of the USGS 7.5-minute quadrangle maps that
cover Pennsylvania divided into 6 blocks. Fields include: Area, Perimeter (Square meters &
meters), Bba_, Bba_id (Two identification fields used internally by the GIS), Name (Eight
character field - first 7 represent the USGS quad name and the last character is the block
number 1-6), Name2 (Place name for each USGS quad map), Block_id (Same as internal code
Bba_id, best used for linking tables within a DBMS structure), Qsb_num (Quad survey block
number, ranges 1-6), Block_type (Three types exist, "B" represents a border block - ie. part
of the block is outside the state boundary, "P" is a priority block ,and " " is a normal
block), Survey_hrs (Reported hours surveyed in each block).
Bbaname.dbf - This file contains identification information for each of the 211 bird species
reported in the Breeding Bird Atlas. Fields include: Common_nam (common name), Genus,
Species, Old_gname (old genus name), Old_cname (old common name) (The last two fields are
included to address name changes that may have occurred since the bba survey.), Elcode
(element code assigned by The Nature Conservancy), Sp_code, Letcode (Four character code
unique to each species), Aou_Num (American Ornithological Union (AOU) assigned number for
each bird. The number corresponds closely, but not exactly, to taxonomic order).
Bbaoccur.dbf - This table indicates the presence or absence of each species within each
Atlas sample block. Fields include: Block-id (Matches IDS with the same field in the GIS
layer), Name (Eight character field - first 7 represent the USGS quad name and the last
character is the block number 1-6), SPxxx (211 fields for each of the Atlas' breeding
species. The xxx matches the numbers listed in the bbaname.dbf table).
Bbadat.dbf - This table lists all species account records for each species within each
Atlas block. Over 300,000 records are listed in this file. Fields include: Quad_num (USGS
7.5-minute quadrangle seven digit identification code), Block_num (Block number in each quad
sheet ranges from 1 to 6), Sp_Code (Same as listed above), Breed-code (Breeding status code.
For details refer to (Brauning 1992)), Year (The year that the highest breeding evidence was
reported for a species in a specific Atlas block), Evidence (Code that represents a
confidence level of each record. Confirmed (4), Probable (3), Possible (2), and Observed (1)
are used), Name (Eight character field - first 7 represent the USGS quad name and the last
character is the block number 1-6), and Block-id.
Complete information about the Breeding Bird Atlas Database project for Pennsylvania, including grid block design, breeding codes, volunteer effort, species accounts, and distribution maps, can be found in: Brauning, D.W. 1992. Atlas of Breeding Birds in Pennsylvania. University of Pittsburgh Press, Pittsburgh, Pennsylvania. While using the digital Breeding Bird Atlas, technical support can be obtained by contacting the Pennsylvania Spatial Data Access system (PASDA) at: firstname.lastname@example.org.