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5.9.  The taxon-group pattern: biological classification of the birds seen

The taxon-group pattern is a set of three attributes used to classify the bird taxonomically:

taxon-group =
(   attribute ab6 { bird-code },     1
    ( attribute rel { "|" | "^" },   2
      attribute alt { bird-code }
    attribute notable { "0" | "1" }? 3
bird-code = xsd:string { pattern="[a-zA-Z]{2,6}" }

The ab6 attribute is required. In most cases it specifies the code corresponding to the name used to describe the classification of the bird. For a discussion of this code system, see Section 3.3, “The taxonomic dimension: what kind of bird?”. For example, the code for Wandering Tattler is wantat:



Normally the rel and alt attributes are absent, and in such cases the ab6 attribute describes a bird assigned to a specific species, family, or other taxon.

However, there are two cases where the kind of bird sighted must be described as two six-letter codes (ab6 and alt) and another code (rel) that describes the relationship between those codes:

  • Species pairs: Sometimes the identification can be narrowed down to a choice of two forms, but no further. For example, sightings of certain flycatchers in the genus Empidonax are often described as “Dusky/Hammond's Flycatcher.” In these cases we use rel='|', for example:

        ab6='dusfly' rel='|' alt='hamfly'

  • Hybrids: The classification is given as a pair of codes with rel='^'. For example, a hybrid of Mallard x Gadwall would be encoded:

        ab6='gadwal' rel='^' alt='mallar'


Flag unusual records with notable='1'. Such records should be highlighted so that readers not interested in routine sightings can more rapidly skim the reports for “the good stuff.”

For species pairs and hybrids, the order is not important. However, retrieval should always ensure that the ab6 code is lexically less than the alt code, so that records of a given pair or hybrid fall in one place and not two.