There are several reasons for assigning codes to forms that are a subset of a standard species:
Subspecies in the strict taxonomic sense, such as Myrtle Warbler (a subspecies of Yellow-rumped Warbler).
Color morphs, such as Blue Goose (a morph of Snow Goose).
Recognizable forms of uncertain taxonomic status, such as Pink-sided Junco (an identifiable form of Dark-eyed Junco).
So we use the term “subspecific form” loosely, to mean any identifiable form that refers to some subset of a standard species. For each such code, enter a line with this format:
The six-letter code being defined.
A less-than (<) symbol.
This is the record type code for a subspecific form
record.
The six-letter code of the standard species that contains this form.
One space, followed by the English name of this form. For multi-word names, use the inverted order, e.g., “Sparrow, Howell's Seaside”.
Bracket species names between underbar (“_”) characters so that when possible
they can be rendered in italics.
Examples of subspecific form lines:
agpchi<grpchi Prairie-Chicken, Attwater's Greater agwtea<gnwtea Teal, American Green-winged alcgoo<cangoo Goose, (Aleutian) Canada axetea<gnwtea teal, (American x European) Green-winged blugoo<snogoo Goose, Blue branth<brant Brant (_hrota_) flcred<comrdp Redpoll, (_flammea_) Common icggul<icegul Gull, Iceland (_glaucoides_) prhlar<horlar Lark, Prairie (_practicola_) Horned