A rapid assessment of Bolivian and Ecuadorian montane avifaunas using 20-species lists: efficiency, biases and data gathered

Abstract

summary Tropical forests are disappearing very rapidly, so there is often not time for thorough quantitative studies. It therefore becomes increasingly important to use rapid, reliable and informative methods which are also adjusted to tropical logistic constraints. In this paper we use data from seven dry and semi-humid temperate forest patches in Bolivia and three humid, temperate forests in Ecuador to estimate the efficiency, potential biases and the amount of information obtained by the 20-species list method, which we applied in a rapid assessment of avian species richness. Even when used without any standardizations, 20-species lists produce more data than simple species lists, particularly on the amount of survey effort, the order of species richness, the relative abundances of species and the α-diversity index. This approach precludes comparisons with lists from other sites. However, when applied with standardization of area, altitude and effort, the method is neither easier to use nor superior to point counts (based upon vocalizations) in combination with dawn chorus tape-recordings. In species-poor habitats, it is more appropriate to use lists of fewer species. The method is recommended due to its simplicity and the increased quantity of information produced, but it requires a reasonable amount of observer competence and is therefore unfit for use by people ignorant of local avifaunas.