The question is; if all of these birds are eliminated suddenly by hunters, which of the following would be the immediate observable consequence?
I think the observable consequence will be that the increased mortality in monkey species B. This is because if the birds are eliminated, then it means the population of mosquito increases since the birds are eliminated, and since the mosquitoes can infect the species B with malaria (they are not immune) then the population of species B will decrease due to high mortality rate.