Naked Science Forum
Life Sciences => Plant Sciences, Zoology & Evolution => Topic started by: Futhark on 24/09/2006 15:57:20
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I know that some birds fly south before vinter comes to Europe to find food and such. But why the heck do they return?
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The weather changes and perhaps need weather to be more acceptible for hunting.. only a guess!
Karen
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quote:
Originally posted by Futhark
I know that some birds fly south before vinter comes to Europe to find food and such. But why the heck do they return?
I do not have a definitive answer, but I can propose some possibilities:
Firstly: simply a matter of sexual selection (the problem of the peacock's tail). If the female flies north, and the male wants to find a mate, he'd better follow her (and visa versa). Those who do not migrate will not find a mate. This may be because of old the bird had a traditional mating ground in the days before migration, and knew it would always find a mate there, but when the climate later changed, it had to change its winter feeding ground, but not its mating territory. In any case, those birds who could make the journey would be the stronger birds, the weaker falling by the wayside along the route, thus guaranteeing that the bird you mate with would be one of the stronger ones.
Secondly: while food in the warmer climes may be adequate, so too would competition, and predators; so when food becomes available again in the cooler climes, it may be safer to use that food source than to stay in the south and risk greater predation, or greater competition. This may be a particular problem when they are breeding, and they eggs and chicks would be especially vulnerable to predation.
Thirdly: it may be that the food source in the south is itself seasonal (e.g. it may consist of some insect larvae, that by the summer months has matured into some less palatable mature insect).
Fourthly: the birds may be looking for a greater variety of diet, where the diet in the south may be plentiful, but may be deficient in some particular nutrient that is only available in the north.
George
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Hi Futhark....
I am sure it's because they just love Danish food !!.."Nørregade" sweets & kippers !!..YAYYYYYYYY !!
Men are the same as women, just inside out !
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Hey George Does this mean if I fly say...wait let me see which direction... i don't know if I fly say North West does that mean my mates gonna follow me..... Geesh Thats the pits...LOL LOL
Karen