Hello all,
I agree that it is amazing that dispersing birds seem to know where they
are going are at least have the knack of heading out to sea and finding
land. However, cattle egrets are relatively capable birds when it comes to
long distance flight.
What I think is truly amazing is how birds like rails (one of the most
successful bird families at dispersing to islands) have managed to do it.
The chance of one rail dispersing across a couple of thousand kilometres of
ocean and hitting land and surviving must be small. So how unlikely is it
that more than one rail can do it within a short enough timeframe for them
to be able to breed and start the seed of a new population and in time a
new species. This has to be one of the miracles of the natural
world...... well I think so anyway.
Some of the best examples of this phenomenon are the "Banded Rails" and the
"Spotless Crakes". There is so little we know about these fabulous
secretive birds. You might have guessed by now that I have a thing about
rails and crakes.
Cheers
Mick Todd
Griffith, NSW
At 01:21 PM 26/08/2003 +1000, wrote:
This whole strategy is the key to the species success. Imagine the first
Cattle Egrets to migrate to New Zealand. How did they know it was out
there? Did they know it was out there? The same could apply to Cattle
Egrets coming to Australia from SE Asia or, even more amazingly, from
Africa to the Americas!. There is a very good chance that these
adventurous birds could perish either by not finding land or finding no
suitable habitat. If the entire population did this then there's a good
chance of total failure. However, by having a mix of migratory strategies
within the population you have birds that are pioneers while there are
others that "stay at home" thus ensuring that if the pioneers don't return
then a nucleus of a breeding colony remains. If all birds returned to the
natal colony then expansion is not likely to succeed. There must be birds
prepared to breed away from the natal colony, joining other egrets - in
the case of the first Cattle Egrets in Australia other species of egret,
to push the frontiers of the empire.
I don't know about you but I find this mighty fascinating stuff!
Cheers
David
David Geering
Regent Honeyeater Recovery Coordinator
NSW National Parks & Wildlife Service
P.O. Box 2111
Dubbo NSW 2830
Ph: 02 6883 5335 or Freecall 1800 621 056
Fax: 02 6884 9382
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