There are less than 150 individuals according to a South African 1990´s survey, most of them found at the Kruger National Park.
It lays one or two eggs which can weight 146 gr and are incubated for about a month in big nests. They don´t breed in colonies.
See the full archaeological study at: http://www.academia.edu/1100015/A_Question_of_Size._A_Remark_on_Early_Attestations_of_the_Ba_Hieroglyph