2:260 Parallel Interpretation
If God intended to say to keep every one of them on the mountain the words could have been something like that: اجعل علی کل جبل کل واحد منھن the word Juz, means part, which indicates that they were no longer alive. moreover as you rightly pointed out, Abraham’s questions can only be answered if the birds are dead and come alive. otherwise, coming of one’s pet bird on his calling has nothing to do with the sign or evidence of resurrection.