Wildlife experts in Manitoba said they are attempting to determine what caused dozens of black birds to fall dead from the sky. Authorities said conservation officers removed more than 50 bird carcasses from a Winnipeg neighborhood Wednesday and the Winnipeg Humane Society took custody of 11 black birds that fell from the sky but remained alive, the Canadian Broadcasting Corp. reported Thursday. Erika Anseeuw, the humane society\'s director of animal health, said the surviving birds seem to be alert, but they are unable to fly or stand up. She said the birds will be euthanized and autopsies will be performed at a pathology lab. Anseeuw said investigators still do not know the cause of the bird deaths, but they may have been exposed to disease or something poisonous. \"My suspicion is this is what it\'s going to be rather than any kind of apocalyptic foretelling of birds falling from the sky,\" she told CBC Radio\'s \"Up to Speed\" program.