Seasonal occurrence of arthropods as a source of food for birds in Finnish Lapland

Abstract

The seasonal occurrence in arthropod abundance was studied in Utsjoki, northernmost Finland, from the viewpoint that arthropods form an important food resource for birds. On ground surfaces, Araneae was the most abundant taxon. The abundance peak of spiders occurred in June. Diptera, which was the dominant taxon in samples collected from dwarf shrubs, had their dominance peak in July. In birch foliage, Homoptera and Coleoptera were most common in June, but lepidopteran and symphytan larvae dominated in late summer. The larvae in pines (Symphyta; Diprionidae and Pamphiliidae) also had their abundance peak in autumn. The role of predation in the seasonality is discussed from the point-of-view of both birds and arthropods.