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1. Day length is probably the main aspect. At
high latitudes, winter day length is very short, not to mention the cold and low
food supply, so it makes sense to follow the summer.
2. Yes that is the only explanation I have ever heard for it
and it appears to be as good or better an explanation as anything else. Since
then the word Rosella has been used for that group of broadtail parrots that
really are all fairly similar and share certain plumage features (most obviously
the cheek patch of different colour and scalloped backs).
Philip
-----Original Message-----
From:
Dr Richard Nowotny <>
To:
Messages Birding-aus <>
Date:
Sunday, 24 August 2003 22:26
Subject: [BIRDING-AUS] 1. Bird
Migration 2. "Rosella"
Two
questions:
1. A semi-birding friend who went with us to see
Travelling Birds asked me
why birds migrate such long, and dangerous,
distances when they seem to
have quite suitable habitat for their needs
(including nesting?) in their
wintering grounds. I started
proffering responses gathered from my reading
over the years, but found
it more difficult than I expected justifying say
a Red-necked Stint
flying from what seems to be relatively food-rich
mud-flats (and
associated coastal habitat) in south-eastern Australia to
somewhere in
northern Asia to breed, and then to endure the equally long
and
hazardous return flight for the non-breeding season.
What are the
scientific reasons/theories for these complex and frequently
very long
migration patterns, ie what are the present (or past - assuming
that it
is now genetically-acquired behaviour, which may not any longer
actually
be necessary) survival advantages of making such a flight, over
the
obvious disadvantages. Does it date back to a previous age when the
advantages were more apparent, or are the present advantages of
migration
still so great that the behaviour continues to be truly
necessary?
2. A much more prosaic matter: Is it correct that
the name "rosellas" is a
corruption of "Rose
Hillers" after the early Botany Bay locale, and
present-day Sydney
suburb, of Rose Hill where they were commonly seen by
early naturalists
and travellers between Sydney Cove and (?)
Parramatta? If not,
what is the correct origin of the name?
Richard Nowotny
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