Premise 1: RWB birds, during their Spring and fall migrations, eat a significant portion of crop.
premise 2: Farmers sought permissions to place small amounts of poisoned rice during spring break.
Conclusion : WildLife agency gave permission despite the concerns that rice could threaten certain species of rare migratory birds

We need to explain why?

A. In the region where the red-winged blackbirds stop, they are the first birds to be present in the spring.
This option says, the RWB birds are the first set of birds to come so it is quite possible that other birds would not be targeted as RWB birds will eat the poisoned rice first-> This explains why Wild life have given the permission and hence correct

B. The poison that farmers want to use does not kill birds but rather makes them incapable of producing viable eggs.
How the poison acts is immaterial to the context as the context is not how to poison will affect the bird but which birds will get affected.

C. Since rice is not raised in Midland Province, few species of birds native to the province normally eat rice.
We are not talking about native birds, we are talking about "rare migratory birds" so this option is out of context.

D. Without the permit, any farmers shown to have set out poison for the blackbirds would be heavily fined.
This is immaterial and out of context

E. The poison that farmers got approval to use has no taste or smell that would make it detectable by birds.
This is immaterial and out of context