Palaearctic migrants in the central Sudan

Abstract

A brief account is given of the topography and climate of the Sudan and a more detailed survey is made of the vegetation and habitats afforded to wintering Palaearctic migrants in the Sahel and Soudan savannah zones in the central Sudan. Climatic conditions during the migration seasons are mentioned and the utilization of habitats by wintering migrants is broadly surveyed.The status of 196 Palaearctic migrant species is treated briefly. The basic observational data are tabulated to summarize observed patterns of migration in terms of date, relative abundance and region (for which purpose the central Sudan is divided into four from west to east). Hitherto unpublished field notes of the authors and their collaborators are used, together with dated observations (including specimens collected) of earlier authors, to provide the fullest data on each species.Moreau's (1967) paradox is discussed as it relates to the Sahel and Soudan savannah zones in the central Sudan, together with the degree of competition with resident African species in those zones. Some disparities between the spring and autumn abundance and d. istribution of Palaearctic migrants are discussed in relation to 40 species ana some tentative views are advanced on the possible reasons for such disparities. Evidence is adduced which points to Lanius minor and Coraczus garrulus (and possibly Circus pygargus, partially at least) having loop migrations, south through the Sudan and north through Arabia, and Falco wespertinus south through the Sudan and north through West Africa. An explanation is offered for the greater volume of water birds observed migrating down‐Nile in spring compared with their volume up‐Nile in autumn, and for the reversed situation observed in the region west of the Nile for these same species.Shelduck Tadorna tadorna is included in the Sudan list for the first time.