Survival of male scarlet-tufted malachite sunbirds (Nectarinia johnstoni) on Mount Kenya and the influence of ornamentation

Abstract

A prediction of handicap and signalling theories is that there should be a positive relationship between ornament size and viability. This prediction was tested in scarlet-tufted malachite sunbirds (Nectarinia johnstoni). These birds are endemic to the high-altitude zones of East African mountains. They are bright iridescent green with elongated central tail feathers and red pectoral tufts. The elongated tail is believed to be a mate choice cue, and the red tufts play a role in aggressive encounters between males: As adults, they feed almost exclusively on the nectar of Lobelia telekii flowers, which males defend from conspecifics. The long term survival of individually identifiable males colour-marked in 1989 and 1990 was investigated. Territorial adult males had an average annual survival rate of 72%, which is at the top of the range reported for tropical birds. The effects of morphology and territory characteristics on male survival were examined by adding covariates to the survival model. This analysis showed that male N. johnstoni with longer tails had a higher probability of survival than did short-tailed males. There was no apparent relation between tuft size or the number of L. telekii inflorescences on the territory and survival. The results presented here suggest that long-tailed males may be of intrinsically higher quality than are shorter tailed males. If this is true then females may benefit by using this trait as a mate choice cue through increased viability of their offspring.