Doi: https://doi.org/10.13157/arla.71.2.2024.ra2
Authors: Aitor GALARZA and Jabi ZABALA
E-mail: aitorgalarzai@gmail.com
Published: Volume 71.2, July 2024. Pages 247-261.
Language: English
Keywords: agriculture, community composition, decline, diet, diversity, feeding strategy and richness species
Summary:
Farmland birds have undergone a severe decline in numbers and range across Europe. Farmland extent in northern Spain was reduced considerably during the past century and remaining patches experienced abandonment or less intensive use. As a consequence, there have been changes in the structure of those remnant patches that may have affected bird community structure. We analysed temporal trends in common breeding bird species richness, diversity, community composition and functional diversity of three Eltonian traits (diet, foraging strategies and body mass) using five surveys of farmland plots conducted between 1982 and 2019 in the Basque Country. In each survey the same 52 farmland plots were sampled, recording breeding species present. to analyse temporal changes we used rarefaction analyses, nmDS, analyses for similarity and GLmms. Our results show that, besides the apparent stability of the community, there was a simplification and homogenisation in its diversity, composition and structure. We detected no temporal shifts in the bird community and most species and trait composition remained the same, but communities became more similar to each other by the regression/disappearance over time of rare or specialist species or those with particular feeding strategies and diets. At the same time, woodland-associated species, omnivores and scavengers became more common. Our results are based on presence/absence of each species and there could be a stronger decline in terms of numbers of breeding birds that was not detected. As possible reasons for this changes, we argue that abandonment of less productive plots and the homogenisation of management and its extension to some landscape features that previously were seldom managed, such as sedgebeds, reedbeds and ditch margins, may have destroyed habitat of specialist species. Our results show that decline of farmland breeding birds and simplification of their communities is also ongoing within remaining Atlantic farmlands.
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