Con - Such terms can indeed be confusing. It is best if serious writing
uses a given set of definitions, either those (helpfully) given by the
writer, or a standard set adopted by reference. Like most definitional
issues there can be unproductive debate about which expression is most
appropriate. My own comments are as follows.
I would leave aside 'dependant' - that is a reporting category ('DY') and,
locally, depends on the parameters specified by those who organise and
direct the reporting process.
'Nestling' is a convenient term for a young bird in the nest, or that might
have prematurely left the nest.
'Fledgling' refers to a bird in the process of leaving the nest and making
its first flight(s).
'Juvenile' and 'immature' are sometimes used simply for obviously young
birds. However, technically they are different plumage stages. It if you
want to know more about this I suggest HANZAB vol 1 pp 28/29. This refers
to variations in usage in the scientific literature. I do not think there
is any point in trying to align chatline usage with the HANZAB conventions
which are intended for detailed plumage descriptions. Technically some
birds do not have an 'immature' stage but proceed directly from juvenile to
'adult'. On the other hand the male Satin Bowerbird has 5 separable
plumages between juvenile and 'adult'.
'Adult' can mean a sexually mature bird or it can mean a plumage stage. If
the latter is intended some species acquire it at the end of the juvenile
plumage stage - or the SBB in year 7.
I see little point in trying for a standard approach in chatline messages.
That would mean that some expressions used informally would have to be
regarded as 'WRONG'.
We have been through all that.
-----Original Message-----
From: Con Boekel
Sent: Monday, 25 August 2014 6:13 PM
To: COG list
Subject: [canberrabirds] Some technical questions about the definition of
life stages in birds
In the trajectory of a bird's life, some stages appear to be straight
forward. For example: egg/not egg; egg/nestling; alive/dead.
But beyond that, it gets tricky.
We have had on the chat line, for example, much discussion about how to
apply 'dependent' to the young of precocial species.
When does a nestling turn into a fledgling?
When does a fledgling turn into a juvenile?
When does a juvenile turn into an immature?
When does an immature turn into an adult?
Does COG (or a reputable scientific body accredited for the purpose by
COG) have a standard set of definitions for a bird's life stages?
regards
Con
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