Reversal of breeding season by lowland birds at higher altitudes in western Cameroon

Abstract

Evidence of breeding during the dry season is given for 31 species of lowland birds in montane and semi-montane areas in western Cameroon. At least 17 of these species are shown to breed in the wet season at lower altitudes in West Africa. This reversal of breeding season may be due to the unusually heavy rainfall and high humidities which cause temperatures to decrease more rapidly with altitude than on mountains with drier climates. Low temperatures and heavy rainfall during the wet season prevent almost all montane species from breeding then, and affect similarly the lowland birds whose ranges overlap with those of montane birds. Breeding season of some lowland species in Cameroon have previously been considered prolonged, but separation of breeding records by altitude reveals clear seasonality.