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Greetings All,
Reading Henry Nix' presidents column in the latest
'Wingspan' caused me to consider this issue. If we are seeing migrants earlier
and they are staying for longer and this is being observed in
the northern hemisphere, there are at least three possibilities.
1. Some species are choosing to spend more time in
the northern hemisphere while others in the south.
2. Some individuals or populations within species
are changing their length of stay in each hemisphere.
3. The departure and arrival times are becoming
broader in range within species or migrants in general. ( This is like a
combination of 1 & 2 but is different to each and maybe should be separate
points for migrants in general and at the species level.)
Does anyone have data on this issue which
illuminates my darkness?
Regards,
Alan
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