Reference

G.J. Broekhuysen, P. G. H. Frost (1968): Nesting Behaviour of the Black-necked Grebe Podiceps nigricollis (Brehm) in Southern Africa - I. The reaction of disturbed incubating birds – Bonn zoological Bulletin - früher Bonner Zoologische Beiträge. – 19: 350 - 361.