Birds in deciduous forests – results of a winter-bird-census in a beech forest near Kiel, Schleswig- Holstein, between 1995 and 2020

Abstract

Part of the ‘Schleswig-Holstein and Hamburg Ornithological Society program’ is winter counting of terrestrial birds (see: www.oagsh.de). In this context, the line transect method was used in a deciduous forest located in the hill country of Schleswig-Holstein for 25 years. The forest consists of middle-age trees, mainly Beeches, and the length of the track was 5 km. During early winter (November), mid-winter December/January), and late winter (February) counts were conducted on three dates. The bird community consisted of 45 different species. The mean density was 85 individuals/km and 13 species were quite common. Common Great Tit Parus major, Brambling Fringilla montifringilla, Eurasian Nuthatch Sitta europaea, Eurasian Blue Tit Cyanistes caeruleus, Marsh Tit Poecile palustris, and Chaffinch Fringilla coelebs were the dominant species with highest number. Seven species were subdominant with lower number. Ten species reached a presence of more than 80 %, while four of them reached 100 %: Common Great Tit, Eurasian Blue Tit, Marsh Tit, as well as Eurasian Nuthatch.

These ten species showed strong changes in population density during 25 years, eight of them with a positive trend, especially Eurasian Nuthatch, Great Spotted Woodpecker Dendrocopos major, and Eurasian Wren Troglodytes troglodytes. The total number of birds per counting day fluctuates by 25 times, so that certain bird communities only exist temporarily. The counting results are highly dependent on the period or time of investigation. Overall, a typical bird community can be detected in this area, Felder Holz, Schleswig-Holstein.

Beech mast has a great impact on bird density; currently this happens every 2.8 years in Schleswig-Holstein. Brambling and Chaffinch can reach 50 % of all birds when Beech seeds are extremely numerous, and other species benefit as well. Two species show irregular invasions, namely Common Wood Pigeon Columba palumbus and Redwing Turdus iliacus. Then they are very numerous but often they are rare and not very present.

The wintry bird community of the Felder Holz is likely to coincide to a considerable extent with similar old beech forests of the country. In contrast, coniferous forests have a very different composition of species.