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Q.

How do migratory birds find their way to other countries?

Tags: way to other countries, migratory birds
Asked by Salila Chandran, 11 Apr '07 06:04 pm
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Answers (2)

1.

One popular suggestion is that the Earths natural magnetic poles help to guide birds in their migrations[2]. How they manage to detect those poles is more difficult to determine.

One theory posits that certain birds brains contain magnetite, otherwise known as iron oxide[3]. Magnetite is a naturally occurring magnetic compound that has been found in animals ranging from bacteria to mammals[4]. With physical magnets in their brains, birds would be able to detect the magnetic fields created by the North and South Poles. Magnetite has been found in the upper beaks of several birds, but until recently, there has been little evidence that the substance is connected with navigation[5].

for furthur reading
http://www.scq.ubc.ca/?p=173
Answered by professor, 12 Apr '07 08:03 am

 
  
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2.

Many species of birds undertake seasonal journeys of various lengths, a phenomenon known as Bird migration.there is a strong genetic component to migration in terms of timing and route, but this may be modified by environmental influences. An interesting example where a change of migration route has occurred because of such a geographical barrier is the trend for some Blackcaps in central Europe to migrate west and winter in Britain rather than cross the Alps. Theoretical analyses, summarized by Alerstam (2001), show that detours that increase flight distance by up to 20% will often be adaptive on aerodynamic grounds - a bird that loads itself with food in order to cross a long barrier flies less efficiently. However some species show circuitous migratory routes that reflect historical range expansions and are far from optimal in ecological terms. An example is the migration of continental populations of Swainson's Thrush, which fly far east across North America before turning south v ...more
Answered by benudhar pradhan, 11 Apr '07 06:37 pm

 
  
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