There is more than one system in use "out there." Those employing
four-letter codes based on the English name of the species are deceptively
similar to one another but use different sets of rules to derive the
codes. Any system inevitably has a degree of subjectivity and
arbitrariness because of the problem of duplicate names exemplfied in the
Trumpeter Swan/Tree Swallow case. The Washington Bird Records Committee
opted to follow the model proposed by Jones in 1992 (Birding 24:377-380),
not because it was inherently better than any other, but simply to avoid
creating yet another system of its own. The codes for the Washington
check-list were published in 1994 (Wash. Birds 3:1-10) as were the rules
for deriving them (Mattocks, in Wash. Birds 3:41-43).

According to that system, Trumpeter Swan is TMSW and Tree Swallow TRSW.
Seventeen other arbitrary code combinations were required to avoid
duplication just for the Washington list. Some examples: Buller's
Shearwater = BLSH (BUSH = Bushtit); Ring-necked Pheasant = RGPH (RNPH =
Red-necked Phalarope); Black-throated Blue Warbler = BUWA (BBWA =
Bay-breasted Warbler); Sage Sparrow = SGSP (SASP = Savannah Sparrow).

The derivation rules are a marvel, and you will love them if you are a
student of scholastic philosophy, or of the finer points of the infield
fly rule. Or maybe a corporate tax attorney.

Hal Opperman
Editor, Washington Birds
halop at u.washington.edy
phone 206-635-0503

On Fri, 6 Dec 1996, Mike Patterson wrote:

>
>
> according to the USFW NBS official code book:
>
> Trumpeter Swan = TRUS
> Tree Swallow = TRES
>
> The rule is: If two birds have the same 4-code, one picks the next easiest
> combination IN BOTH SPECIES that resolves the conflict.
>
>
> >
> >With all this talk about Trumpeter vs Tundra Swans I have noticed that
> >everyone seems to use TRSW as the code for the Trumpeter. There is a
> >conflict with that code and the Tree Swallow. It is my understanding that
> >TRSW is used for the Tree Swallow and TMSW for the Trumpeter Swan.
> >
> >Hugh Jennings
> >Bellevue, WA
> >
> >
>
> --
> *********************************** I was of three minds
> * Mike Patterson, Astoria, OR * like a tree
> * mpatters at orednet.org * in which there are three blackbirds.
> *http://www.pacifier.com/~mpatters* -Wallace Stevens
>