The main food sources of the birds( the plentiful recourses within the environment occupied by the species)
One reason is for safety! in case you get stranded in a body of water you can keep yourself afloat
The one that is correct for the effect of linkage on recombination is : C. It reduces the percentage of recombination
In linkage on recombination it only use part of the Recombination that doesn't exist on the parent. Doesn't necessarily have to be 50 %
hope this helps