Realm: Terrestrial
Climate: Polar/Temperate
Biome: Boreal forests / Taiga
Central latitude: 65.975000
Central longitude: 16.050000
Duration: 20 years, from 1963 to 1982

356 records

40 distinct species

Across the time series Anthus trivialis is the most frequently occurring species

Methods

Densities of bird populations were estimated by territory-mapping in study plots. With the exception of thrush species and most non-passerine species, that were censused by nest counts. Field work usually started about 10 June and lasted for about three weeks. A certain shift of study plots occurred during the 20-year period. but more than half of the area was the same and plots usually fluctuated in parallel. The observer went along tracks distributed all over the forest studied recording all audible an visible observations of birds, mostly singing males. Results were expressed in territories per km2. The census-takers of the study plots have also been responsible for the transect work which is performed as follows: The observer goes along tracks distributed all over the 9 km2 of the forest under investigation and records all audible and visible observations of birds, mostly singing males. The tracks were not marked out and therefore their position in the forest may have shifted locally between seasons. This has probably not biased the field data significantly because the observer had to make no less than 80 kilometers, on the average, of line transecting to collect the required amount of data. The size of the area covered by the transects was not considered as the data are only used to calculate the percentage share of each species in the total amount of observations. To estimate these values for the most sparse of the regularly breeding species with sufficient accuracy requires at least 1500 observations (Enemar & Sjöstrand 1967) which in the birch forest takes an average of 30 hours of field work. This minimum number was not achieved in the first two seasons.

Citation(s)

@Article{BioTIME_cit481, Study_id = {711}, Citation_id = {481}, Author = {Enemar, A. and Nilsson, L. and Sj{\"o}strand, B}, Journal = {Annales Zoologici Fennici}, Pages = {321-338}, Title = {The composition and dynamics of the passerine bird community in a subalpine birch forest, Swedish Lapland. A 20-year study}, Volume = {21}, Year = {1984}, Language = {English} }