Tom M. van der Have¹ & Bennie van den Brink²

1Working Group International Waterbird and Wetland Research (WIWO), c/o Driebergseweg 16c, 3708 JB Zeist, The Netherlands, e-mail vogelnl@vogelnl.antenna.nl; ²Nederlandse Ringcentrale, Netherlands Institute of Ecology, PO Box 40, 6666 ZG Heteren, The Netherlands

van der Have, T.M. & van den Brink, B. 1999. Barn Swallows in Africa: Effects of rainfall on body condition and speed of moult. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr., Durban: 229. Johannesburg: BirdLife South Africa.

The long-term decrease in Barn Swallows Hirundo rustica numbers has been attributed to various factors in the breeding and non-breeding areas. This study aimed to identify the effects of rainfall variability on body condition and rate of moult in Botswana (1993 to 1995) and Ghana (1996/97) in December to January. Rainfall varied dramatically between years in Botswana, resulting in reduced roosting habitat in 1993/94 and 1994/95, and dry periods in 1992/93 and 1994/95. Body mass was high in 1992/93, but much lower in the other years. In 1992/93 and 1994/95 body mass decreased when rainfall ceased, and increased gradually after rainfall, which triggered termite flights. Rate of moult between years correlated with average body mass: rate of moult was highest in 1992/93 and lowest in 1994/95. In Ghana significant differences were found in moult index, wing length and weight between northern and southern locations and with the non-breeding population in Botswana. It is concluded that body mass and speed of moult in Barn Swallows wintering in Botswana is the result of the interaction between rainfall, affecting food availability, and the amount of available roosting habitat, determining flight distance to foraging areas and bird density.

Note: Full paper not submitted