Population densities, biomass and trophic relations of birds in the pre-Saharan steppe of Tunisia

Abstract

Twenty-two species of birds occurred in the study area between 1975 and 1978. Two species of lark, Calandrella rufescens and Galerida cristata, accounted for most of the bird life on the plot, numerically and in terms of biomass. Visits by residents of nearby areas made up a nearly continuous and at times considerable contribution. Winter visitors were nearly negligible and migrants were important only briefly in the spring of some years. There were more birds in spring than at other times of year and there was a general trend towards increasing numbers from 1975 to 1978 particularly during winter. Most of the birds were entirely insectivorous, or were primarily insectivorous omnivores with granivory being of lesser importance. Estimated annual food consumption was 1534 g dry weight/ha/year. The total biomass of birds was low (8·6–31·3 g/ha) in comparison to many habitats. Birds do not have a very great impact on the economy of this ecosystem.