Food habits and niche overlap in three alpine passerine birds, South Norway

Abstract

The three most common passerine birds in alpine habitats on the Hardangervidda plateau, South Norway, are the Meadow Pipit Anthus pratensis , the Wheatear Oenanthe oenanthe , and the Snow Bunting Plectrophenax nivalis . Analyses of stomach content showed that invertebrates are the main food of these species, but the Wheatear and the Snow Bunting also eat Empetrum berries, and the Snow Bunting becomes a seed eater in October when snow has arrived and the two other species have left the area. Seasonal changes in diet were related to phenological changes in the availability of food items. Adult Tipulidae were for instance taken by all species during the swarming period in July. Overlap in food choice was considered medium for all three species combinations. The Snow Bunting overlapped only slightly with the two other species in altitudinal distribution, habitat choice and territory. However, the Meadow Pipit and the Wheatear overlapped strongly in these parameters. Since their reproduction was successful, we assume that these two species can live together with strongly overlapping niches due to a surplus of available invertebrate food. All three species are able to change their food choice rapidly and are thus well adapted to manage unpredictable conditions in a harsh, high altitude ecosystem.