Nest predation is little affected by parental behaviour and nest site in two African Sylvia warblers

Abstract

Parental behaviour and nest site are supposed to affect nest predation in birds. Few nest visits and high nest attentiveness are assumed to lead to low predation rates. Poorly concealed nests are thought to be more likely to be preyed upon than well concealed nests. Studies on the relationship between parental behaviour, nest site, and nest predation are rare and none have, so far, been conducted in the Afrotropics. We studied the effect of nest site, nest visitation rate, and nest attentiveness on the nest predation rate of the two tropical warblers Sylvia boehmi and Sylvia lugens in Kenya. Parental behaviour and predation on nests of 13 breeding pairs of both species were observed daily in two consecutive breeding seasons. In both species, parental activity at the nest was low [0.9 trips to the nest in 30 min during incubation, maximum 4.6 (S. boehmi) and 5.8 (S. lugens) trips to the nest in the nestling stage]. Predation rates in both species were high (Mayfield nest success 19.4 and 33.2%). Our analysis revealed only weak evidence for an effect of nest site, nest visitation rate, and nest attentiveness on the predation rate. It is suggested that smaller clutches of tropical in comparison to northern temperate birds result from lower feeding rates in tropical ecosystems with high predation rates (Skutch’s hypothesis). The underlying mechanism could not be proven in this study.