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3.6. Kind of bird

In order to understand how we represent the kinds of bird seen, see A system for representing bird taxonomy, which describes a system of six-letter codes for describing kinds of birds.

That system allows for single kinds of birds, “species pairs” (e.g., we think it was either a Hammond's or Dusky flycatcher), or hybrids (e.g., it looked like a hybrid of Blue-winged and Cinnamon teal). In general, the representation is a triple (form, rel, altForm). The form is the first or only six-letter code. The rel value is the relationship code, blank for single forms, “×” for hybrids; and “/” for species pairs. If the relationship code is not blank, the altForm value is the second form's six-letter code. If there are two codes, we stipulate that form < altForm, so we don't have to search twice to pick up a given hybrid or pair.

Additionally, this database sometimes represents the sighting's age category (adult, immature, or female/immature) or sex category (male or female).