DOI: 10.5061/dryad.tdz08kq3q
title: Invertebrate communities across wader habitats in Europe

description: Grassland breeding waders have been steadily declining across Europe.
 Recent studies indicating a dramatic decline in grassland
 invertebrates' abundance and biomass, the key food of most grassland
 wader chicks, suggest a likely driver of the demise of waders. While
 agricultural intensification is generally inferred as the main cause for
 arthropod decline, there is surprisingly little information on the
 relationship between land use intensity and total arthropod abundance in
 grasslands. Here, we explored those relationships across several key wader
 breeding habitats by surveying ground-active, aerial and soil-dwelling
 invertebrate communities in five European countries that range from
 natural undisturbed bogs to intensively managed grasslands. Using maximum
 vegetation growth and soil moisture content, we investigated how they
 shape the size of the invertebrate community within and across different
 countries. We found predominantly positive relationships between grassland
 invertebrate abundance, biomass and body weight with increasing vegetation
 growth and soil moisture. Maximum vegetation growth was strongly
 positively related to ground-active invertebrate abundance and biomass and
 abundance of soil-dwelling invertebrates (mainly earthworms). Body weight
 of aerial invertebrates furthermore increased with increasing maximum
 vegetation growth. Our results provide little support for the hypothesis
 that agricultural practices associated with intensification of grassland
 management result in an abundance decline of invertebrate prey for wader
 chicks. Conservation practices aiming to enhance wader chick survival
 require a careful balancing act between maintaining habitat productivity
 to secure high prey abundance and keeping productivity low enough to
 maintain open swards that do not need to be cut before chicks have
 fledged.
description: Data was collected in 64 sites in five countries across mainland
 Europe: France, the Netherlands, Poland, Estonia and Finland. To
 standardize habitat types and to make sure that results would be relevant
 for wader conservation, all sites had been hosting breeding waders
 (particularly the near-threatened black-tailed godwit) in the years before
 sampling, as indicated by local experts. Eighty-one percent of the sites
 hosted black-tailed godwit territories in the year we surveyed these
 sites; all contained at least one territory of a wader species, and
 breeding densities varied substantially. We aimed to include sites that
 varied as much as possible in land-use intensity both within countries and
 between countries, and sampled bogs and fens (natural habitats with no
 agricultural use), coastal and floodplain grasslands (semi-natural
 habitats that are grazed or mown but do not receive any inputs) and
 improved grasslands varying in management intensity (none to high
 fertilizer input). In each site, we surveyed aerial, ground-active and
 soil-dwelling invertebrates, sampled vegetation biomass and measured soil
 moisture content at twelve-day intervals throughout the local wader
 breeding season.