[CT Birds] Pre-adult Bird age and plumage stages
Mntncougar at aol.com
Mntncougar at aol.com
Mon Jul 30 08:26:16 EDT 2012
There is a very interesting (to me) discussion on the Michigan bird list
regarding the terminology used to describe birds which are NOT adults. In
fact it addresses some things I have always wondered about when I've read and
heard discussions regarding the topic.
This is the original question asked:
What's the difference when one uses the term 'juvenile' or 'immature' or
is it just a matter of semantic preference?
But as you will see, the discussion broadened out a bit. Here is the first
information given as a response. It is taken from NYC Birds Wiki: (Here's
the actual link in case it's messed up -
"See the Wikipedia page for _bird anatomy_
(http://en.wikipedia.org/wiki/Bird_anatomy) including feather groups.
Plumages and Molts
Bird molts occur at different times of the year in response to feather
wear, and to change plumages. The terminology for plumages varies. In these
pages I've used a very simple definition of plumages:
* Juvenile - the first plumage of a young bird with a covering of
contour feathers (as opposed to down etc)
* Immature - any that is not in full adult plumage. Technically
"immature" also includes "juvenile" but in the descriptions I use it in the
sense of any immature plumage distinct from juvenile plumage.
* Adult non-breeding - any adult plumage distinct from the breeding
* Adult breeding - adult in breeding plumage
Birds exhibiting fairly straightforward molt sequences molt out their
feathers twice a year - once prior to attaining breeding plumage and once to
replace the worn breeding plumage. Not all feather groups are replaced in all
molts, and the sequence can depend on age. Molts in migratory birds may
occur before, after or during migration so potentially the plumages
encountered can be quite complex. Similarly wear and bleaching (most common in gulls)
can become a significant factor.
An excellent discussion of molt and aging terminology can be found at the
_Ontario Field Ornithologists_ (http://www.ofo.ca/plumages.htm) site.
Notably they define:
* Juvenile (as above)
* Immature - any non-adult plumage including juvenile
* Subadult - largely synonymous with immature
* Adult non-breeding
* Adult breeding
* First winter, first summer, second winter, second summer etc -
deserves an explanation. For birds that molt twice a year and have extended
immature plumages it is usually possible to observe distinct plumages at each
stage. First winter is the first non-breeding immature plumage (the winter
following the summer the bird was born). First summer is not the summer
the bird was born, but the summer following the year the bird was born. And
so on and so forth. Large gulls and eagles in particular display a large
array of immature plumages
(up to fourth winter in the case of some large gulls).
* First year, second year etc - for birds that molt once a year this
plumage extends from late summer to the following summer. First year is the
late summer that the bird was born in through the summer of the following
* Eclipse - this is really the non-breeding plumage of ducks,
acquired in late summer or early fall. It is most obvious in males which acquire a
female-like plumage. Some ducks adopt eclipse plumage only for a short
time, while some take quite a while to come out of it - it's not unusual to
see Northern Shovelers with distinct traces of eclipse plumage in early
winter. By late winter ducks are usually in their full breeding plumage with no
trace of eclipse.
* First calendar year - this works on the Jan 1st to Dec 31st cycle.
The first year is the year the bird is born in. This is less frequently
used, but has some role in disambiguating the meaning of "first summer" in
It's the definition of first summer that usually gives most people the
wrong impression (i.e. a lot of people think it's the juvenile plumage and it
Note that there is an excellent and thorough definition of plumages and
molts following the Humprey and Parkes system that is overkill for most
amateur discussions of bird plumages. Here non-breeding plumage is "basic",
breeding plumage is "alternate", juvenile plumage is "juvenal", the final
unchanging plumages for basic and alternate are called "definitive", so
"definitive basic" would necessarily be an adult non-breeding plumage. The plumage
sequence is juvenal - basic - alternate - basic - alternate - etc ... Molts
are referred to in terms of the plumage they become e.g. "first prebasic"
before first basic, "definitive prealternate" before definitive alternate."
However there was a second post that addressed the question somewhat
differently and answered (or at least shed some light on) my own questions on
the subject. I Believe this was actually taken from "The Auk": (The link:
"The use of the terms "juvenal" and "juvenile."--Uncertainty and confusion
exist as to the use of these terms in regard to birds and their plumages.
dictionaries both words are given synonymous meanings of young or youthful
and a youth (noun); but "juvenal" is now very rare or obsolete in its
general sense and has become almost exclusively a technical term
specific plumage stage in birds. The term "juvenal plumage," meaning the
of true feathers following the neossoptile or downy stage, seems to have
with Jonathan Dwight (see Ann. New York Acad. Sci., 13: 99, 106, 1900).
later explained his selection of "juvenal," rather than the more familiar
because the latter word "has a less exact meaning" (Auk, 19: 251, 1902),
used to indicate immaturity in general. Dwight's term "juvenal plumage" has
been adopted almost universally by American ornithologists, including
like Humphrey and Parkes (Auk, 76: 15, 1959), favor abandoning Dwight's
nomenclature in other respects. In Great Britain "juvenile plumage" is
the same sense (H. F. Witherby et al., The handbook of British birds, vol.
1, p. xxiii;
London, Witherby, 1941.). However much current ornithological literature,
the United States and abroad, uses "juvenile" with the general meaning of
that is, for any stage prior to the definitive adult (J. Van Tyne and A.
Fundamentals of ornithology, p. 572; New York, Wiley and Sons, 1959. M. E.
Rawles in A. J. Marshall et al., Biology and comparative physiology of
birds, vol. 1,
New York and London, Academic Press, 1960; see pp. 198-9.). Sometimes--and
is particularly true of specimen labels--"juvenile" or "juv." indicates
only the younger
stages of immaturity, but without restriction to the first generation of
feathers. Some American ornithologists insist, nevertheless, on a fine
which seems to me both unnecessary and productive of confusion; they use
as an adjective for the first feathered plumage, but adopt "a juvenile" as
for a bird in juvenal dress. Others suggest that "juvenal-plumaged bird"
to avoid ambiguity. It seems to me shorter and simpler (and equally
to say "a juvenal" for an individual in juvenal plumage. The only objection
advanced is that "juvenal" is adjeciival in form and origin; but this
equally to "juvenile." As a matter of English usage and grammar both words
convertible into nouns. Such locutions as "an immature" or "a downy" are
In the interest of precision and brevity, I recommend that those who employ
"juvenal" to indicate the plumage should also use the term "a juvenal" for
a bird in
that plumage. Because of its ambiguity, "juvenile" should be avoided in
studies of plumage or where a specific age stage is intended.*--E. EIS•N•
Museum of Natural History, New York 24, New York.
* Without reference to the finer distinctions relating to noun vs.
adjectival use, the
editor is one who considers "juvenal" a definite statement of stage (i.e.,
relating to a
bird in first plumage) and "juvenile" a general indication of comparative
youthfulness. These are the meanings that these terms (hopefully) carry in
Anyone have a quibble or anything to add?
mntncougar at aol.com
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