Akkervogels

Wildtierfreundliche Landwirtschaft

Seit 1992 setzt die schweizerische Landwirtschaft vermehrt auf die Ökologie. Höhere Bodenfruchtbarkeit, sauberere Gewässer, tiergerechte Haltung von Nutztieren und eine wachsende Vielfalt von Kleinlebewesen sind nachweisbare Erfolge dieses Wandels. Für heimische Wildtiere ist eine Trendwende dennoch in weiter Ferne: Die Hälfte der Vogelarten des Kulturlandes ist weiterhin bedroht. Die ökologischen Ziele der Schweizer Landwirtschaft sind noch nicht erreicht.

Het deuntje van het voorjaar dreigt te verdwijnen

Iedereen kende 'm. Het voorjaar begon met zijn deuntje, iedereen floot dat riedeltje mee. En nu staat-ie op de Rode Lijst." De constatering van Ruud Foppen over de veldleeuwerik Alauda arvensis komt er met enige verbazing uit. Het hoofd onderzoek van SOVON Vogelonderzoek Nederland en medesamensteller van de Vogelbalans 2008 noemt de teloorgang van het oer-Hollandse zangvogeltje 'gigantisch'.

De grauwe gors is feitelijk uitgestorven in Nederland

De grauwe gors Miliaria calandra is feitelijk uitgestorven in Nederland. De vogel, die vroeger vaste gast was op akkergebieden en hooilanden, wordt nu eigenlijk alleen nog 's winters in groepen waargenomen. En dan vooral op de zogeheten hamsterakkers waar langer gewassen staan om het de in Limburg levende hamsters naar de zin te maken. Tot die slotsom komt Sovon Vogelonderzoek Nederland.

Skylark, Corn Bunting, Tree Sparrow and Northern Lapwing in sharp decline across Europe

The Wild Bird Indicator 2005 shows that on average over the last twenty-five years, farmland birds such as the Eurasian Skylark Alauda arvensis, Corn Bunting Miliaria calandra, Eurasian Tree Sparrow Passer montanus and Northern Lapwing Vanellus vanellus, have declined sharply in number across Europe. As a whole from 1980 to 2003, common farmland birds on average fell in number by 28%.

Farmland birds showed a significant decline across Europe between 1990 and 2000

Between 1990 and 2000, farmland birds showed a significant decline across Europe, a trend not shared by bird assemblages of other habitats over the same period. Mean trends for each farmland species in the period 1990–2000 were positively correlated with trends over the period 1970–1990, and there was little change in population trajectory for most species over the 30-year period. Of the 58 species classed by an independent assessment as being primarily birds of farmland, 41 showed negative overall mean trends across Europe in 1990–2000. There was a significant negative correlation between mean national trends of all farmland species and indices of national agricultural intensity.

Dramatic decline of an insectivorous passerine, the Whinchat

Insectivorous farmland passerines have declined steadily throughout most of western Europe over the past decades. The Whinchat Saxicola rubetra, an insectivorous passerine species of grassland, has undergone one of the most dramatic declines among farmland birds. The recent intensification of farming practices has led to a decrease in the availability of grassland invertebrates in general, and of important Whinchat chick-food in particular, even in remote Alpine valleys. This has a negative effect on reproductive success.

The explanation for farmland bird declines - Loss of insect food could be a major factor

Research into the declines of some species of farmland birds have shown that there is no single reason, but that different species have reacted to different factors, and that often, declines are associated with more than one factor impacting on a species simultaneously. Loss of insect food could be a major factor.

Increased pesticide use has been a key cause of Grey Partridge decline

Population declines in many farmland bird species have been documented during the last quarter of the 20th century in parts of Europe and North America where agricultural intensification has been most marked. 'Intensification' is multivariate, difficult to define precisely, but taken to subsume all those advances that have allowed farmers to increase primary productivity. Increased pesticide use on arable land has been a key cause of Grey Partridge Perdix perdix decline through its impact on the availability of insect foods to chicks, and hence on reproductive success.

Linking agricultural practice to insect and bird populations: a historical study over three decades

There is continuing debate about the impact of agricultural practices on farmland wildlife. In particular, it has been postulated that a general decline in insect abundance linked with intensification of agriculture may have contributed to farmland bird decline. While some autecological studies have supported this hypothesis, larger-scale and long-term studies are needed.

• Suction traps mounted on 12·2-m towers (Rothamsted-type) have been sampling aerial insects for nearly 40 years throughout the UK. Their catches are correlated over large spatial scales. We analysed insect catch data from a single suction trap run for 27 years in a rural location in Scotland, and showed that insect numbers have changed significantly over time, although non-linearly. The multivariate data set (numbers from the 12 common arthropod groups) was summarized using principal components analysis (PCA) to extract three components explaining 62% of the variation.

• We also used PCA to describe agricultural change, using published agricultural data for eight measures of farming in Scotland. Arthropod abundance and principal component (PC) scores were significantly related to the agricultural PC scores as well to summary climatic measures.

• Using Scottish data from the British Trust for Ornithology Common Birds Census, we extracted three PC to describe the time-dependent average densities of 15 common farmland birds in Scotland. Measures of bird density were significantly related to insect abundance and PC scores and, independently, to measures of agriculture and climate.

• These data from a broad suite of species provide support for linked temporal change between farmland birds, invertebrate numbers and agricultural practice in Scotland. Although entirely correlative, the results are consistent with the view that agricultural change has influenced birds through changes in food quality or quantity. The work also shows how large-scale invertebrate sampling, in this case using suction traps, is useful for monitoring farmland biodiversity.

De patrijs verdwijnt door insectenschaarste uit grote delen van Nederland

Patrijzen Perdix perdix zijn standvogels van open agrarisch gebied, heidevelden en hoogvenen. Akkerland is het meest in trek. Tot ver in de 20e eeuw was de patrijs een algemene broedvogel, met een populatie van naar schatting enkele honderdduizenden broedparen. Vanaf de jaren vijftig wordt gesproken van een afname, die met name in de jaren zestig en zeventig schrikbarende vormen heeft aangenomen en welke nog steeds voortduurt. Rond 1975 bedroeg het totaal aantal broedparen minder dan 50.000 en begin jaren negentig was het verder geslonken tot 20.000-25.000 paar. Inmiddels kunnen we spreken van nog slechts 10.000 paren. Volgens de Vogelbescherming is de populatie sinds 1980 met 95% geslonken. De afname is het sterkst in het oosten en midden van het land. Het zuidwesten komt er relatief goed vanaf, al is ook hier sprake van een niet mis te verstane afname. Inmiddels is de patrijs uit grote delen van Nederland aan het verdwijnen. Ook in België, Luxemburg, Frankrijk, Engeland, Ierland, Duitsland, Zwitserland en Polen is de soort ernstig bedreigd (gegevens Birdlife International, zie bijlage).

Patrijzen eten zowel plantaardig als dierlijk voedsel, maar de jongen leven de eerste weken louter van insekten en ander klein gedierte.