This message was on the Birding ID Frontiers listserve. I don't know how
many tweeters are on that listserve, but I thought the following might be
of interest to tweeters. I've looked at the website mentioned in the
post, and it's great.

Mike Donahue
Seattle
---------- Forwarded message ----------
Date: Sat, 4 Oct 1997 20:55:37 -0400
From: Jean Iron <jeaniron at GLOBEDIRECT.COM>
To: BIRDWG01 at LISTSERV.ARIZONA.EDU
Subject: [BIRDWG01] Plumage, Molt and Age Terminology

More and more birders are using the Humphrey and Parkes terminology to
precisely describe the molts and plumages of birds. Often the identification
of a rare gull or shorebird depends on knowing its exact plumage and age.
The H&P system uses terms like Definitive, Basic and Alternate to describe
plumages and terms like Prebasic and Prealternate to describe molts. These
terms may seem difficult to use at first, but they are a joy to use once
mastered. The H&P terminology is used by the ABA in Birding, Palmer's
Handbook of North American Birds, The Birds of North America series and most
recently in the Ontario Bird Records Committee Report for 1996 in the August
1997 issue of ONTARIO BIRDS 15(2):47-66.
I thought that some readers would be interested in the article by
Ron Pittaway on Plumage, Molt and Age Terminology that appeared in the
Feburary 1995 issue of OFO NEWS 13(1):4-5. This article compares the
terminology used in the National Geographic Society field guide with that
used by Humphrey and Parkes. It has easy to understand definitions of the
terms Juvenal, Basic, Alternate, Supplemental, Definitive, etc. There is
also a handy comparison chart of the two plumage and molt terminologies.
This article is now available on the Home Page of the Ontario Field
Ornithologists: www.interlog.com/~ofo

I hope you'll find it a useful reference, Jean

Jean Iron
President, Ontario Field Ornithologists
Don Mills, Ontario
jeaniron at globedirect.com