Re: Oh Canada, the Loons are suppose to fly south, not NORTH!

Reverse migration is a phenomenon in bird migration. Although some
large birds such as swans learn migration routes from their parents, in
most small species, such as passerines, the route is genetically
programmed, and young birds can innately navigate to their wintering
area.

Sometimes this programming goes wrong, and the young bird, in its first
autumn, migrates on a route 180o from the correct route. This is shown
in the diagram, where the breeding range of a hypothetical Asian
species is shown in yellow. The correct migration route to the
wintering grounds in south east Asia is indicated in red.

If a bird sets off in the opposite direction, shown by the orange
arrow, it will end up in Western Europe instead of South East Asia.
This is a mechanism that leads to birds such as Pallas's Warbler
turning up thousands of kilometres from where they should be. Keith
Vinicombe suggested that birds from east of Lake Baikal in Siberia
(circled) could not occur in western Europe because the migration
routes were too north-south.

Most of these lost young birds perish in unsuitable wintering grounds,
but there is some evidence that a few survive, and either re-orient in
successive winters, or even return to the same area.

An article in British Birds by James Gilroy and Alexander Lees in
September 2003 suggested that misorientation occurs in random
directions, but differential survival in different directions combined
with asymmetric observer coverage leads to the observed distribution of
vagrants. Although "reverse migration" per se may occur, it is unable
to explain the occurrence in Europe in autumn of Asian vagrants that
winter in East Africa, or the rarity of many southern European species
in the UK that winter in West Africa. Furthermore there is little
evidence for reverse migration in North America where there is more
uniform observer coverage.

****that's not totally true, isolated reports of reverse migration in
north america are commonplace, but usually only report one or two birds
in a given incident. what they don't see in NA is large numbers or
flocks of reverse migrants.


the extraterrestrial wrote:
chuck, I'll try tomorrow to post some detailed information on the loon.

but it might interest you to know that occasionally with migratory
birds the bird flies the wrong direction. it's thought to be due to CNS
or genetic abnormalities, they don't really understand it. birds
migrate according to poorly understood mechanisms related to sunlight,
star positions, and the earth's magnetic field.

and birds are quite a bit different from mammals in terms of the
organization of the cerebral cortex, so it's hard to relate to exactly
what is going on...they're sort of in their own CNS realm.

so what you get in reverse migration is for example a warbler that
flies north for the winter instead of south to the caribbean.

those birds typically aren't going to survive..LMAO..they'll either
freeze to death, starve to death, or fall prey to a year-round resident
raptor looking for easy pickings.


4man12 wrote:
lol, on da phone wit da stark raving lunatic.

.

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