There are several reasons why a user might want to collapse multiple kinds of birds into a single row in the generated report.
To update old, disused names. For example, between the 7th edition of the AOU Check-list and the 42nd supplement, what was Oldsquaw became Long-tailed Duck. In this case, no splits or lumps were involved, just a change of the standard name.
To make reasonable assumptions about forms that have been split. For example, Boat-tailed Grackle was split some time ago, and it is a safe assumption that all the old New Mexico records for Boat-tailed Grackle pertain to what is now called Great-tailed Grackle.
To effectively lump two or more forms. For example, a user may wish to combine records of the Gambel's and Mountain race of White-crowned Sparrow with records for undifferentiated White-crowned Sparrows.
To complicate matters, the CBC database also includes
records for hybrids (e.g., Cinnamon × Blue-winged
teal) and species pairs (e.g., Hairy/Downy Woodpecker).
In general, the CBC database represents kinds of birds as
a triple (
form is a required six-letter code
for the first or only kind of bird. For most records,
rel is blank, but in the case of
hybrids it is
"x", and in the case of
species pairs it is
"/", and in these two
cases the second kind of bird is encoded in the
We define the term alias to mean a rule that all records for a given kind of bird should be combined with records for a different kind of bird.
In the most general form, an alias is a pair of (
alt_form) triples, such that any record
matching the first triple is considered to be the same
kind of bird as described by the second triple.
Here are some example aliases from an alias set for New Mexico records. The first translates Oldsquaw records to Long-tailed Duck. The second treats records for “Eastern/Western Screech-Owl” as Western Screech-Owl.
(("OLDSQU", " ", ""), (("LOTDUC", " ", "")) (("EASOWL", "/", "WESOWL"), ("WESOWL", " ", ""))