The correct answer is D. however.
You want to show contrast between these two sentences, and the only word among these which can do that is <em>however. </em>The sentences are each other's opposites - even though there is an increase of eagles in the Southeast, there is still a decline in their numbers overall.
D. It makes april seem to the speaker like a mindless person to emphasize the contradictions of the month
the souls still shiver is figurative because souls dont physically shiver
I think mostly D. I hope this helped :)
