Influence of livestock grazing on meadow pipit foraging behaviour in upland grassland

Abstract

Changes in grazing management are believed to be responsible for declines in populations of birds breeding in grassland over the last decades. The relationships between grazing management regimes, vegetation structure and composition and the availability of invertebrate food resources to passerine birds remain poorly understood. In this study, we investigated the foraging site selection of meadow pipits (Anthus pratensis L.) breeding in high intensity sheep-grazed plots or low intensity mixed (i.e. sheep and cattle)-grazed plots. We sampled above-ground invertebrates, measured vegetation height and density and conducted a vegetation survey in areas where meadow pipits were observed to forage and areas that were randomly selected. Birds foraged in areas with a lower vegetation height and density and in areas containing a lower proportion of the dominant, tussock-forming grass species Molinia caerulea. They did not forage in areas with a total higher invertebrate biomass but at areas with preferred vegetation characteristics invertebrate biomass tended to be higher in foraging sites than random sites. The foraging distance of meadow pipits was higher in the intensively grazed plots. Our findings support the hypothesis that resourceindependent factors such as food accessibility and forager mobility may determine patch selection and are of more importance as selection criteria than food abundance per se. Food accessibility seems to become an even more important selection criterion under high grazing intensity, where prey abundance and size decrease. In our upland grazing system, a low intensity, mixed grazing regime seems to provide a more suitable combination of sward height, plant diversity, structural heterogeneity and food supply for meadow pipit foraging activity compared to a more intensive grazing regime dominated by sheep. r 2009 Gesellschaft für Ö kologie. Published by Elsevier GmbH. All rights reserved. ZusammenfassungMan nimmt an, dass Veränderungen in der Beweidungswirtschaft während der letzten Jahrzehnte für die Abnahme der Populationen von Vögeln verantwortlich sind, die auf Grünland brüten. Die Beziehungen zwischen verschiedenen Arten der Beweidungswirtschaft, der Vegetationsstruktur und -zusammensetzung und der Verfügbarkeit von Invertebraten-Nahrungsressourcen für Singvögel ist bisher kaum bekannt. In dieser Studie untersuchten wir die

Predictive mapping of Meadow Pipit density using integrated remote sensing data and an atlas of vascular plants dataset

“…In the months that follow, i.e. May and June, grass vegetation is higher, so food is not as easily accessible and detectable for Meadow Pipits (Butler & Gillings 2004, Douglas et al 2008, Vandenberghe et al 2009, and foraging mobility is restricted (Devereux et al 2006, Douglas et al 2008. We suspect that lowland meadows, which are mowed once or twice per year, provide low vegetation; in lowland and upland pastures, low vegetation is also achieved by grazing.…”

Does breeding success lead meadow passerines to select late mown fields?

“…birds would tend to concentrate in late mown patches where breeding failure is expected to be lower. An alternative hypothesis was that birds use a ''decision rule'' not entirely based on prior experience to select nesting sites and would be influenced rather by habitat characteristics such as the height or density of grass cover (Warren and Anderson 2005;Davis 2005;Kirsch et al 2007;Vandenberghe et al 2009) or the foraging context (Abrahams 1986;Krebs and Inman 1992). Several studies have indeed shown that breeding birds tend to be attracted by species-specific sward structure or by invertebrate prey availability (Wittenberger 1980;Söderström et al 2001;Nocera et al 2007); but local abundance and reproductive rates may be unrelated (Winter and Faaborg 1999;Fletcher and Koford 2002).…”

Habitat associations of young Black Grouse Tetrao tetrix broods

“…For example, Black Grouse chicks had significantly higher survival in areas of moorland where grazing had been reduced than in grazed moorland (Calladine et al 2002). However, the effects of vegetation height and structure on Black Grouse are unlikely to be straightforward, and multiple scenarios are plausible, including trade-offs between predation risk, invertebrate food availability and chilling effects during cold, wet weather (Vandenberghe et al 2009, Signorell et al 2010, Patthey et al 2012. For instance, in the Central European Alps, brood-rearing female Black Grouse selected a mosaic of grassy shrubland with scattered trees in preference to open grassland with higher arthropod abundance (Signorell et al 2010, Patthey et al 2012.…”

“…vegetation that has high heterogeneity in height and vertical density; e.g. Baines 1996, Vandenberghe et al 2009). …”