A system for encoding bird field notes |  |
A system for encoding bird field notes | |
To represent what kind of birds we see, we're fortunate to have the American Ornithological Union's Check-list of North American Birds as a standard for the classification of birds.
However, the AOU Check-List is not
a static entity. Every two years a new revision appears,
and every few revisions a new major edition appears. At
this writing, the Seventh Edition is the base checklist,
with supplements through the Forty-Seventh Supplement
adding later corrections. The author has built a
complete infrastructure for tracking all these versions;
it is described in A
system for representing bird taxonomy. The fundamental item used from this system is the
six-letter bird code, such as VERFLY for
Vermilion Flycatcher or BRWHAW for
Broad-winged Hawk.
Fundamentally, we prefer to assign each sighting to a
biological taxon in the AOU's classification. Most
sightings are identified to species, but we may use
larger or smaller taxa. For example, what in English we
call “falcon sp.” (falcon species) can be
assigned to family Falconidae. In another case we might
see a well-marked race such as Audubon's Warbler, which
is a form of the species Yellow-rumped Warbler. The
six-letter codes in the nomenclatural base system allow
for assignment to any level: these examples would be
encoded as FALCON and
AUDWAR respectively.
Two additional wrinkles complicate the process of assigning sightings to taxa:
Some observations can be narrowed down to two forms but no further. For example, it is often quite difficult to separate Hammond's Flycatcher and Dusky Flycatcher in the field. We refer to this situation as a species pair. Literature references might show this form as “Hammond's/Dusky Flycatcher.”
Some of the individuals out there are hybrids. In this case we can generally guess at the two parent forms, e.g., “Mallard x Gadwall”.