Abstrakti
Summary: Habitat-specific variation of abundance in bird species visiting the feeding sites of Finland in 1991–2023
Birds were counted all over Finland at 984 winter feeding sites by voluntary bird-watchers during 33 winters by the Finnish version of the garden bird survey. Counting lasted from 1 October to 30 April, covering 14 half-months. For each species, at least the maximum number of individuals simultaneously observed on the “best day” was reported from each half-month. It indicated abundance in this study.
Data were analyzed for three zones: Southern Finland (250 km from south to north), Middle Finland (450 km) and Lapland (400 km). Each feeding site was classified, based on surrounding area, into one of the three habitats: rural, open countryside or forested countryside. Well-studied half-months within each site and winter were averaged for three seasons: autumn (October and November), winter (from December to February) and spring (March and April). Data were further divided into three 11-year periods: 1991–2001, 2002–2012 and 2013–2023, resulting in species-specific densities of 61 species in four dimensions (three zones x three habitats x three seasons x three 11-year periods.
Long-term variation of the number of feeding sites, seasonal temperatures and the annual import of food for birds are shown (Figs. 1–2). Avifaunal structure of the feeding sites was studied by the principal component analysis on the correlation matrix of average density of 61 species in 27 classes (3 zones x 3 habitats x 3 11-year periods), separately on the square-root transformed density of autumn, midwinter and spring. The results of the three PCAs were notably similar. The first principal component Pc1 represented the general variation of density of the species. The second component Pc2 indicated movement from northern to southern fauna and the long-term increase of faunally southern elements. The third component Pc3 indicated gradient from open and rural habitats to open and forested countryside (Fig. 3). The species-specific score values of Pc3 from the midwinter and the autumn correlated strongly (Fig. 4). The rapports of the species are presented in ascending order of their midwinter score value of Pc3 (Table 1).
The diagrams of the most informative 39 species have three subfigures (1) Kaupunkiasutus (Rural), (2) Aukeahko maaseutuasutus (Open countryside) and (3) Metsäinen maaseutuasutus (Forested countryside). These contain columns for three zones Lappi (Northern Finland). Väli-Suomi (Middle Finland) and Etelä-Suomi (Southern Finland). Each subfigure of a zone presents seasonal variations of abundance during three monitoring periods of 11 years (on the Y-axis Yksilöä/paikka means average amount of birds per site). Codes of the seasons are below the X-axis: S (autumn), T (midwinter) and K (spring). Colours and symbols of 11-year periods are explained beside their median yeas 1996 (black), 2007 (blue) and 2018 (red).
Each species text starts by listing general frequency (percentage of the sites where the species was observed) in four habitats: B1 Rural, B2 Open countryside, B3 Forested countryside and B4 “Wild forest”. Small data of B4 were not included into the diagrams but are in more simple form in Table 2.
Birds were counted all over Finland at 984 winter feeding sites by voluntary bird-watchers during 33 winters by the Finnish version of the garden bird survey. Counting lasted from 1 October to 30 April, covering 14 half-months. For each species, at least the maximum number of individuals simultaneously observed on the “best day” was reported from each half-month. It indicated abundance in this study.
Data were analyzed for three zones: Southern Finland (250 km from south to north), Middle Finland (450 km) and Lapland (400 km). Each feeding site was classified, based on surrounding area, into one of the three habitats: rural, open countryside or forested countryside. Well-studied half-months within each site and winter were averaged for three seasons: autumn (October and November), winter (from December to February) and spring (March and April). Data were further divided into three 11-year periods: 1991–2001, 2002–2012 and 2013–2023, resulting in species-specific densities of 61 species in four dimensions (three zones x three habitats x three seasons x three 11-year periods.
Long-term variation of the number of feeding sites, seasonal temperatures and the annual import of food for birds are shown (Figs. 1–2). Avifaunal structure of the feeding sites was studied by the principal component analysis on the correlation matrix of average density of 61 species in 27 classes (3 zones x 3 habitats x 3 11-year periods), separately on the square-root transformed density of autumn, midwinter and spring. The results of the three PCAs were notably similar. The first principal component Pc1 represented the general variation of density of the species. The second component Pc2 indicated movement from northern to southern fauna and the long-term increase of faunally southern elements. The third component Pc3 indicated gradient from open and rural habitats to open and forested countryside (Fig. 3). The species-specific score values of Pc3 from the midwinter and the autumn correlated strongly (Fig. 4). The rapports of the species are presented in ascending order of their midwinter score value of Pc3 (Table 1).
The diagrams of the most informative 39 species have three subfigures (1) Kaupunkiasutus (Rural), (2) Aukeahko maaseutuasutus (Open countryside) and (3) Metsäinen maaseutuasutus (Forested countryside). These contain columns for three zones Lappi (Northern Finland). Väli-Suomi (Middle Finland) and Etelä-Suomi (Southern Finland). Each subfigure of a zone presents seasonal variations of abundance during three monitoring periods of 11 years (on the Y-axis Yksilöä/paikka means average amount of birds per site). Codes of the seasons are below the X-axis: S (autumn), T (midwinter) and K (spring). Colours and symbols of 11-year periods are explained beside their median yeas 1996 (black), 2007 (blue) and 2018 (red).
Each species text starts by listing general frequency (percentage of the sites where the species was observed) in four habitats: B1 Rural, B2 Open countryside, B3 Forested countryside and B4 “Wild forest”. Small data of B4 were not included into the diagrams but are in more simple form in Table 2.
Alkuperäiskieli | suomi |
---|---|
Lehti | Linnut-vuosikirja |
Vuosikerta | 2023 |
Sivut | 6-21 |
Sivumäärä | 16 |
ISSN | 1455-674X |
Tila | Julkaistu - 2024 |
OKM-julkaisutyyppi | B1 Kirjoitus tieteellisessä aikakauslehdessä |
Tieteenalat
- 1181 Ekologia, evoluutiobiologia