[Taxacom] migration and tectonics

[John Grehan]

Those interested in dispersal might like the discussion of migration in
relation to tectonics of the Tasman region in Biogeography of Australasia:

?The distribution of the cuckoo Chrysococcyx...lucidus is shown in Figure
6.15. Each year populations migrate between southern Australia (breeding)
and New Guinea..., and between New Zealand (breeding) and the Coral Sea
islands....Whether or not the two groups of populations warrant separate
subspecies is controversial. In addition, the details of the migration
routes around central eastern Australia are unclear, and banding or
molecular studies are needed. But the birds have allopatric, sedentary
relatives on Rennell Island...Vanuatus and New Caledonia, consistent with
evolution of the whole complex by simple vicariance.

The migrations of New Zealand Chalcites lucidus are among the longest
trans-oceanic migrations of any landbird. Hutton (1872) suggested that the
birds follow routes that represent former coastlines. These have changed
over time while the birds? annual migrations have remained the same,
following old shores of the Lord Howe Rise, Norfolk Ridge and other
features that are now submerged. Repeated strandings of migrating marine
mammals at certain localities suggest that the same process applies here.
McCann (1964) mapped what he termed the ?coincidental distributional
pattern? of strandings in New Zealand and this would be explicable if
whales and dolphins were following old features of the continental shelf
that have been uplifted.

In addition to Chalcites, there is one other cuckoo breeding in New
Zealand, Urodynamis...taitensis. In winter this species migrates to islands
in the south-west and south-central Pacific: Palau and New Guinea to the
Marquesas, Pitcairn and Line Islands (Ellis et al., 1990). This defines a
vast Pacific range, but does not include Australia or islands west of New
Guinea. In fact, no birds breeding in Australasia migrate to Asia beyond
Wallace?s Line (Dignle, 2008) and this is another aspect of migration that
probably reflects tectonics.?