Why is he not letting her around them? she doesnt want to be by herself

i have 4 ducks 2 brown and 2 white ducks m/f so they would be a couple ok,,the first night my white female got ate by some  animal... so i went to get another one ok,,,, at first they wouldnt let her hang out with them but finally they did  then all was good but just here lately the white male duck is not letting the female come around and chasing her off from them,,,,,could some one tell me what is problem is,,,,? he needs to gets his own ducks in a roll or else -------------------help tell me .