Fair comment Paul, especially re the miserable excuse for 'summer' over
the past few weeks. There's no doubt that birds 'fine-tune' their
departures based on current conditions - temperature, drought measures
etc - but the driving force for migration departure is actually day
length. eg a given species may have as a 'default' setting the number of
minutes of daylight on 28 March (chosen randomly, there's no
significance in that); it's ready to go then, but if things are crook it
might head off earlier and if all is balmy there may be no pressing need
to go for another couple of weeks or so. However given that the classic
date for peak YfHE departure here is Anzac Day, I have to agree that
this is still a bit surprisingly early, cool nights notwithstanding. The
food situation wouldn't appear to be too bad, compared with recent summers.
Sadly we could only really get a definitive answer by asking the
honeyeaters....
cheers all
Ian
Martin et al,
We've not even reached 30'C this February in Canberra, after some heat
in January. Observing my own garden and gardens of friends there are
a lot of autumn flowering plants that are weeks early (I have leaves
up on some bulbs that are literally a couple of months early!). I am
assuming that the migratory patterns of the yellow honeyeaters would
be following the flowering of certain plants (i.e their food sources),
or else temperature patterns (this February has been more like a usual
March I would think) so I personally don't find it much of a surprise
to see any migratory bird being a bit confused this year.
Just mentioning this as I had seen a couple of people express surprise
as to why things would be different this year...... if you're an avid
gardener at the moment it is obvious that things are a tad mixed up!!
<grin>
--
Ian Fraser,
Environment Tours; Vertego Environmental Wordsmithing
GPO Box 3268, Canberra, ACT 2601
ph: 61 2 6249 1560 fax: 61 2 6247 3227
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