Answers

2015-04-21T20:41:56+05:30
When the climaical conditions are not suitable/favourable,scarcity [food ,water,etc],harm from the predator ..................
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2015-04-25T14:23:37+05:30
The birds migrate because due to shelter, food, climatic condition,to reproduce in suitable place, escape from the predators  E.T.C.


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