Habitat use and diet of skylarks (<em>Alauda arvensis</em>) wintering in an intensive agricultural landscape of the Netherlands

In recent decades, Skylark (Alauda arvensis) populations in Europe have declined sharply due to agricultural intensification. Insufficient reproduction rates are one reason. Increased winter mortality may also be important, but studies outside the breeding season are scarce and mostly limited to the UK. We studied habitat selection of wintering Skylarks in an agricultural area in the Netherlands. We monitored Skylarks between November 2008 and March 2009 on 10 survey plots including 77 different arable fields and permanent grasslands and covering in total 480 ha. We simultaneously measured food availability, vegetation structure and field boundary characteristics. We also analysed 158 faecal pellets collected on potato and cereal stubble fields to relate Skylark diet to seasonal changes in food availability and foraging habitat. We show that cereal stubble fields larger than 4.3 ha, surrounded by no or low boundary vegetation and a density of dietary seeds of more than 860 seeds m(-2), were most suitable for wintering Skylarks. Skylark group densities were low on permanent grasslands and on maize stubble fields. Densities of dietary seeds were highest in soils of potato stubble fields followed by cereal stubble fields, grasslands and maize stubble fields. Skylarks showed a strong preference for cereal grains, but their proportion in the diet fell sharply at the end of November, indicating that cereal grains were depleted and birds had to switch to less profitable food sources, such as weed seeds and leaves. We conclude that Skylarks wintering in agricultural landscapes possibly suffer from a lack of energy-rich food sources and only a few fields provide sufficient food. Conservation measures should strive to improve the wintering situation by creating food-rich habitats such as over-winter stubble with a rich layer of weeds on large fields and localised in open areas

Hibernation of predatory arthropods in semi-natural habitats.

Non-crop habitats provide important resources for natural enemies. Many natural enemies hibernate in non-crop habitats, from which they may colonise arable fields in the spring. Spring colonisation ensures annual repopulation of the crop with natural enemies, allowing them to keep pace with the development of pest populations. The availability of non-crop habitats can, therefore, be crucial to successful conservation biological control. We quantified the density of overwintering natural enemies near organic Brussels sprout crops in five different non-crop habitats (short grassy field margin, herbaceous field margin, herbaceous field margin under a tree line, ditch and forest). Soil and litter samples of non-crop habitats were taken at two sites. One site was located in an open agricultural landscape, the other in a landscape dominated by mixed forest. Insects belonging to Staphylinidae, Araneae, Carabidae, Coccinellidae and Dermaptera were the most abundant. Mean densities of predatory arthropods were higher in the open agricultural landscape (290 predators m−2) than in the forested landscape (137 predators m−2). Herbaceous habitat types supported the highest densities of overwintering predators (up to 400 predators m−2), whereas densities in the forest were lowest (10 predators m−2). These results indicate that herbaceous non-crop habitats are important refugia for predators and may play a vital role in conservation biological control

Persistent negativeeffectsofpesticidesonbiodiversityandbiological control potentialonEuropeanfarmland

International audienceDuring thelast50years,agriculturalintensificationhascaused manywildplantandanimalspeciestogoextinctregionally or nationallyandhasprofoundlychangedthefunctioningofagro-ecosystems.Agricultural intensificationhasmany components, suchaslossoflandscapeelements,enlargedfarmand fieldsizesandlargerinputsoffertilizerandpesticides. However, verylittleisknownabouttherelative contributionofthesevariablesto thelarge-scalenegativeeffectson biodiversity. Inthisstudy,wedisentangled theimpactsofvariouscomponentsofagriculturalintensificationonspecies diversity ofwildplants,carabidsandground-nestingfarmlandbirdsandonthebiologicalcontrolofaphids. In aEurope-widestudyineightWestandEastEuropeancountries,wefoundimportantnegativeeffectsof agriculturalintensificationonwildplant,carabidandbirdspeciesdiversityandonthepotentialforbiologicalpest control,asestimatedfromthenumberofaphidstakenbypredators.Ofthe13componentsofintensificationwe measured,useofinsecticidesandfungicideshadconsistentnegativeeffectsonbiodiversity.Insecticidesalsoreduced the biologicalcontrolpotential.Organicfarmingandotheragri-environmentschemesaimingtomitigatethenegative effectsofintensivefarmingonbiodiversitydidincreasethediversityofwildplantandcarabidspecies,but–contrary to ourexpectations–notthediversityofbreedingbirds. We concludethatdespitedecadesofEuropeanpolicytobanharmfulpesticides,thenegativeeffectsofpesticideson wild plantandanimalspeciespersist,atthesametimereducingtheopportunitiesforbiologicalpestcontrol.If biodiversityistoberestoredinEuropeandopportunitiesaretobecreatedforcropproductionutilizingbiodiversity- based ecosystemservicessuchasbiologicalpestcontrol,theremustbeaEurope-wideshifttowardsfarmingwith minimaluseofpesticidesoverlargeareas

Appendix B. Results of the analysis with a reduced data set.

Results of the analysis with a reduced data set

Appendix C. The α and β diversities within each region disregarding agricultural intensification.

The α and β diversities within each region disregarding agricultural intensification

Appendix A. Details on the breeding-bird sampling protocol.

Details on the breeding-bird sampling protocol