Taxonomic and functional diversity of farmland bird communities across Europe: effects of biogeography and agricultural intensification

Abstract

In eight European study sites (in Spain, Ireland, Netherlands, Germany, Poland, Estonia and Sweden), abundance of breeding farmland bird territories was obtained from 500 × 500 m survey plots (30 per area, N = 240) using the mapping method. Two analyses were performed: (I) a Canonical Correspondence Analysis of species abundance in relation to geographical location and variables measuring agricultural intensification at field and farm level to identify significant intensification variables and to estimate the fractions of total variance in bird abundance explained by geography and agricultural intensification; (II) several taxonomic and functional community indices were built and analysed using GLM in relation to the intensification variables found significant in the CCA. The geographical location of study sites alone explains nearly one fifth (19.5%) of total variation in species abundance. The fraction of variance explained by agricultural intensification alone is much smaller (4.3%), although significant. The intersection explains nearly two fifths (37.8%) of variance in species abundance. Community indices are negatively affected by correlates of intensification like farm size and yield, whereas correlates of habitat availability and quality have positive effects on taxonomic and functional diversity of assemblages. Most of the purely geographical variation in farmland bird assemblage composition is associated to Mediterranean steppe species, reflecting the bio-geographical singularity of that assemblage and reinforcing the need to preserve this community. Taxonomic and functional diversity of farmland bird communities are negatively affected by agricultural intensification and positively affected by increasing farmland habitat availability and quality.

Appendices

Appendix 1

See Table 4.

Table 4 Criteria used to define breeding bird territories according to the species’ detectability and breeding behaviour

Appendix 2

See Table 5.

Table 5 Ground-nesting farmland bird species considered in this study and functional categories used to calculate Simpson’s diversity indices for ‘Foraging Strategy’, ‘Nesting Strategy’, ‘Diet Type’ and ‘Migration Status’

Appendix 3

See Fig. 3.

Fig. 3

Canonical axes resulting from the Canonical Correspondence Analysis (CCA) of farmland bird abundance in relation to a study site as predictor and intensification variables as co-variables (pure effect of study site), b to intensification variables as predictors and study site as co-variable (pure effect of intensification), and c only to intensification variables as predictors (mixed effect). BW black-tailed Godwit, CB corn bunting, CE corncrake, CLA crested lark, CU curlew, FTW fan-tailed warbler, GBU Great Bustard, L lapwing, LBU Little Bustard, MA mallard, MO montagu’s harrier, MP meadow pipit, MR marsh harrier, MW marsh warbler, OBU ortolan bunting, OC oyster catcher, P grey partridge, PH pheasant, Q Quail, RL red-legged Partridge, S skylark, SC stonechat, SN snipe, STL short-toed lark, TPI tawny pipit, W northern weather, WC winchat, WL woodlark, Y yellowhammer, YW yellow wagtail. AES Agri-environmental schemes, Carabrich carabid richness, Farm Size farm size, Insectic insecticide, MeanFieldSize Mean field size in landscape, Nfert n fertiliser, NrCrops number of crops, Percent Arable cereal surface in landscape, Soil Disrupt soil disrupting, WeedRich weed richness, Yield yield