birding-aus Re: Migration of noisy friarbirds

["Judy Caughley" <>]

Hi Fiona and all,
When we see concentrations of birds or other animals (e.g. kangaroos, mice
etc), we tend to jump to the conclusion they have migrated from somewhere.
But one day I sat down and thought if all the animals within a radius of 5
km moved to the central 2 km  what would the effect on density be. The
answer is quite amazing and suggests that local movements can really explain
many of the variations in density we see. I'm not denying migration in birds
like yellowfaced honeyeaters etc  - the winter exodus from Canberra to the
coast is spectacular - but for species that are mobile, concentration on
food sources is not unlikely.
Cheers
Judy

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