Akkervogels

Een rijk geïllustreerd boek, geschreven door zeven deskundigen op het gebied van landbouw en vogels en samengesteld door het Centrum voor Landbouw en Milieu (CLM), dat het vogelleven op landbouwgrond wereldomvattend in beeld brengt, is per 1 april 2010 verschenen. Het boek besteedt aandacht aan de vele bedreigingen waaraan vogels blootstaan. In de bijlage de lijst van vogels die in het boek staan.

A richly illustrated book written by seven experts in biology and agriculture and compiled by the Dutch Centre for Agriculture and the Environment (CLM) reviewing birdlife on farmland on a global scale has been released on 1 April 2010. The book identifies the threats facing farmland birds and explores the available opportunities for their protection. A bird list is enclosed.

A study identified two factors that may limit breeding productivity of the Reed Bunting Emberiza schoeniclus, which is in significant decline in England since the 1990s: ground vegetation providing concealment from nest predators and availability of invertebrate prey for chicks. The increased use of pesticides may have reduced invertebrate densities on most farmland.

There has been a massive 95% decline in the UK Tree Sparrow Passer montanus population between 1974 and 1999. The nestling diet of Tree Sparrows is largely composed of invertebrates. It is possible that due to agricultural intensification in the late 20th century and increased use and effectiveness of insecticides there has been a decline in invertebrate prey, rendering large areas of farmland as suboptimal breeding habitat for Tree Sparrows.

There has been a large population decline of the song thrush Turdus philomelos in Britain during the last three decades, which has reduced breeding densities on farmland by nearly 70% between 1968 and 1999. Survival of birds in their first year of life after fledging was shown to have a great impact on population changes. Changes in survival in the first winter are sufficient to have caused the song thrush population decline. Earthworms and other soil-dwelling invertebrates form a large component of the diet of song thrushes, particularly between December and May. Earthworms move deeper into the soil and/or become inactive during periods of cold weather and hence become less available as prey for song thrushes. Reduced availability of invertebrate food could explain reduced survival in the winter.

The Ortolan Bunting Emberiza hortulana has suffered a general decline across much of Western Europe in recent decades. In Switzerland, only one population remains in sub-Mediterranean shrub-steppe on the south-facing slopes of the Rhone Valley (Valais). We aimed to collect data on foraging ecology of the last Swiss Ortolan Buntings during reproduction. All males showed a disproportionate use of conventional maize fields that had been treated with herbicides, while also exhibiting an avoidance of meadows and riparian vegatation. The observed patterns of habitat use may be driven by unavailability of optimal foraging habitat, with birds being forced to use the best of a poor set of options. Structurally, it was shown that birds foraged in areas with a high proportion of bare ground, as well as moderately dense overhead vegatation. These areas did not support higher arthropod abundance, suggesting that food accessibility rather than food abundance dictated habitat selection.

Breeding and wintering abundance of corn buntings Miliaria calandra in an agricultural landscape of Alentejo (southern Portugal) was assessed in relation to agricultural intensification and other environmental variables during 1994-1997. Bird abundance was lowest in intensively managed farmland in both seasons.