From the introduction:
"Part I of the present report was published four years ago. It contained introductory remarks, general information on the area investigated, and the systematic accounts of mammals, reptiles and amphibians collected and observed outside the national parks during the Lund University Congo Expedition 1951-1952. It was originally intended to publish this work in two volumes. This plan has been abandoned because the ornithological material is too large. The first systematic section of the birds appears in the present volume. In a third volume the passerine birds will be treated, followed by a general account including ecological and zoogeographical discussions.
Since Part I was published the author has again worked in the Belgian Congo and Ruanda-Urundi. The second expedition covered the period November 1958-May 1959. Also during this second expedition the main task was the study of physiological and climatological factors in connection with the nuptial migration of Palaearctic Motacilla flava wintering around the equator. Beside this work we continued to make ecological and biological observations of all vertebrates around us. Records were kept on habitats, relationships between biotopes and vertebrates, and interspecific relations and distribution of vertebrates in different mountains (volcanoes). Observations were also made on the behaviour and the biology of vertebrates. The following notes are some of the results of the bird studies made during both expeditions. Many ecological and biological features in certain species are, however, not mentioned in this part, but will be dealt with in connection with the general account in Part III."