Methodology
The first two paragraphs below borrow freely from Mattocks (1988).
What is a Breeding Bird Atlas (BBA)?
The basic objectives of the breeding bird atlas are to develop a map of the nesting
occurrence of each species known to breed in the four-county area, and to make these
maps available in a socially useful and scientifically valid manner. BBA is a presence/absence
study, not a quantitative study. It seeks to determine whether or not a species
is present in a given area (atlas block) in the breeding season and to weigh the
evidence for its actually nesting there. But it is not designed to measure population
density.
Breeding Evidence
The BBA is based on the fieldwork of volunteer participants who record evidence
of breeding for each species occurring in an atlas block, following a standardized
protocol employed by atlas projects in dozens of other counties, states, and countries.
Each observation during the nesting season can be classified in one of four categories:
OBserved, POssible breeder, PRobable breeder, or COnfirmed breeder. The specific
type of breeding evidence is recorded on field cards under one or another of these
categories, as appropriate, using standard codes (see Table 1). On our maps, each
species is depicted at the highest evidence level at which it was recorded by BBA
observers on each individual atlas block. Only POssible, PRobable, and COnfirmed
records are reflected on the maps; the OBserved category is not used.
- OBserved
-
O – Species observed, but no evidence of breeding. (In practice, used in cases
where the observer believes that the individual observed is a migrant, vagrant,
or post-breeding dispersant; or that no suitable nesting habitat is present on the
atlas block.)
- POssible
-
√ – Species in suitable habitat during nesting season
-
X – Singing male present in suitable habitat
- PRobable
-
M – Multiple singing males (7) found during one visit
-
P – Pair observed in suitable habitat
-
T – Territory established; also, singing male present at same location on
two dates a week or more apart
-
C – Courtship behavior, copulation, or enlarged cloacal protuberance
-
V – Visiting probable nest site
-
A – Agitated behavior from adults
-
N – Nest-building or excavation of nest cavity
- COnfirmed
-
PE – Physiological evidence: brood patch or egg in oviduct
-
DD – Distraction display
-
UN – Used nest or eggshell (of positive identity)
-
FL – Recently fledged young incapable of sustained flight
-
ON – Occupied nest: adults entering, leaving, or incubating, but nest contents
unseen
-
FN – Adult bringing food to nest
-
FS – Adult removing fecal sac from nest
-
NE – Nest with eggs
-
NY – Nest with young seen or heard
Table 1 — Breeding Evidence Definitions and Codes
Data from Washington Department of Fish and Wildlife (WDFW)
Through the generosity of WDFW, breeding records from their Heritage and Spotted
Owl databases have been included in the BBA. Those for the years 1987–1994
are reflected on the maps in Smith et al. (1997). To these we have added the records
from 1995 to the end of the four-county atlas period (2002 for Island County, 2000
for the other three counties). These databases contain detailed information about
breeding sites of many sensitive species. By agreement with WDFW, our maps and data
tables for Greater Sage-Grouse, Northern Goshawk, Ferruginous Hawk, Golden Eagle,
Peregrine Falcon, Prairie Falcon, and Spotted Owl have been generalized to full
township/ranges, to help safeguard these species from disturbance. For information
concerning records from these databases, please contact:
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Washington Department of Fish and Wildlife
-
600 Capital Way N
-
Olympia, WA 98501-1091
Integrity of data
In 1998, a block-by-block comparison was made of the hardcopy field cards for King
and Kittitas Counties with the final database of BBA records used for the maps of
the bird volume of the Washington Gap report (Smith et al. 1997). This exercise
revealed an unacceptable number of discrepancies. Many of these can be attributed
to lost or otherwise absent field cards, while others appear to result from data-entry
errors ranging from random keystroke mistakes to entire field cards having been
entered under the wrong atlas-block coordinates. As a result of this comparison
it was decided to create a fresh database for the four-county atlas, starting with
the reentry of all of the data from the original field cards of the first (statewide)
atlas phase. It was also decided that no data from new fieldwork would be entered
except on the basis of a hardcopy record in standard field-card format, thus permitting
the later verification of any record.
After cessation of fieldwork the completed database was cross-checked against the
field cards for a random sample of 60 blocks, disclosing three errors in 2,113 datapoints.
This error rate of <0.15 percent was considered acceptable.
Anomalous and outlier records were reviewed upon data entry and again by the authors
of the species accounts. Almost without exception such records were at the POssible
level, reflecting isolated observations of single birds in atypical locations. In
many instances reviewers decided to downgrade these to OBserved, reasoning that
they represented migrants or birds otherwise not breeding on a particular block.
The smaller number of cases where such records have been allowed to remain on the
maps are individually discussed in the species accounts. It should be noted, too,
that reviewers have upgraded many records from OBserved to POssible in cases where
this action was clearly justified by date of observation and by habitat. In addition,
observers were occasionally asked to confirm unusual sightings to be certain they
did not result from recording errors in the field.
Availability of Data
Maintained in the form of Excel spreadsheets, the four-county database of bird records
was limited to the fields necessary to generate the maps—atlas block, species
name, and highest breeding-evidence level (PO, PR, CO)—and to track observer
hours and survey years. These data can be viewed and downloaded from the present
website. The Seattle Audubon Society maintains the archive of field cards for the
entire BBA (1987ff.) and will make these cards available to qualified researchers
who are seeking more detailed information about individual records. Correspondence
should be sent to:
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Chair, Science Committee
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Seattle Audubon Society
-
8050 35th Avenue NE
-
Seattle, WA 98115
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