Mortality in South African Cattle Egrets Bubulcus ibis from 1951 to 1987

Of 46,160 birds ringed in South African heronries from 1951 through 1987, 481 were subsequently recovered (recovery rate: 1.04%). Most of these birds were ringed in the Western Cape (N = 173), KwaZulu-Natal (N = 142) and Gauteng (N = 106). The age of the recovered birds ranged from 0 to 23 years. Almost two thirds were 0-2 years old, and only 1.2% were 15 years or older. The average age of the recovered birds was 4.9 years (N = 465). The mortality rate was highest in their first and second year (31-36%). Nearly one third of the birds recovered (N = 134) were sick or injured, and 30.6% had been shot. Relatively low mortality, a long life span and relatively low predation pressure may contribute to the great success of the Cattle Egret in colonising various parts of the world. The paper presents the initial state for the likely future evolution of the distribution of the species.