Intra- and inter-annual variation in body mass of two species of weavers in an Afrotropical environment

ABSTRACT Capsule We describe the effects of sex, daily rainfall and temperature, seasonality, and breeding stage on body mass variation in two species of weaver in a tropical African environment. Aims To investigate the effects of sex, weather conditions, seasonality, and breeding stage on body mass of the Village Weaver Ploceus cucullatus and Northern Red Bishop Euplectes franciscanus in Amurum Forest Reserve, Central Nigeria. Methods Biometric data were extracted from a Constant Effort Sites database of over 15 years and daily rainfall and temperature data were obtained from Jos Metrological Center. We used a general linear mixed model to determine the effects of sex, rainfall, temperature, and season on body mass variation of the two species within and across years, and differences in body mass of females of the two species within and across years with daily rainfall and temperature, and season during the different incubation stages. Results The body mass of males was higher than that of females in both species. Daily rainfall and mean temperature were negatively related to body mass in Village Weavers, while in Northern Red Bishops rainfall was positively related to body mass. In both species, female body mass varied according to brood patch status: female Village Weavers were heavier during the egg-laying stage compared to the non-breeding season; female Northern Red Bishops weighed more at incubation or brooding stages and less during the chick rearing stage when compared to the non-breeding season. The body mass of females did not correlate with daily rainfall and temperature, or season. Conclusions Our results showed the effect of sex on body mass in both species of weaver. The variation in body mass of these species during breeding, and with local weather conditions, suggests how the species manage body mass within a tropical African environment.