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Ottens H.J.,Stichting Werkgroep Grauwe Kiekendief | Kuiper M.W.,Wageningen University | Van Scharenburg K.,van Loghemstraat 50 | Koks B.J.,Stichting Werkgroep Grauwe Kiekendief
Limosa | Year: 2013

As elsewhere in Europe, the Skylark once was among the most abundant bird species in Dutch farmland, but over the past decades the species has decreased by 96%. Between 2007 and 2012, we studied a Skylark population in the northeastern part of the province of Groningen, to identify the causes of this decline and to evaluate the effect of an agrienvironment scheme on the population. Agri-environment measures occupied 3.3-5.5% of the total farmland in the study area and comprised mainly field margins: strips of land ≥9 m wide, sown with mixtures of herbs and grasses. The dominant crops in the study area were winter cereals (55% of area), intensively managed grassland (18%), maize (8%) and lucerne (4%). Field margins contained more invertebrate prey than the surrounding crops, and observations of adult foraging flights showed a strong preference for foraging in margins. For nesting Skylarks favoured lucerne and grassland; winter cereals were used only until the end of May, when the height of the crop exceeded 40 cm. The number of fledglings produced per nesting attempt was highest in lucerne (1.14) and lowest in grassland (0.14). Population modeling predicted an annual population growth rate of 0.84, and the observed number of breeding pairs decreased 63 in 2007 to 38 in 2012. To achieve population stabilization, the average nest survival should increase from the current 13% to approximately 35%. The results indicate that the Skylark population is not sufficiently aided by field margins as a stand-alone agri-environment measure. The main bottleneck for the population is a shortage of safe nesting habitat. After winter cereals have become too tall, the only abundantly available nesting habitat with short vegetation is grassland, but this is mown too frequently to allow successful nesting. Lucerne is a better alternative but only present in low quantities. We therefore recommend that future agri-environment schemes increase suitable nesting habitat, particularly in June and July. This can be realised by increasing the area of lucerne, spring cereals or no-till winter cereals. However, considering that many Skylark populations depend on grassland for breeding, the introduction of measures on grassland is expected to be essential. Possibilities are grass fallow (extensively managed grassland), or a delay of the second or third cut on conventional fields by 10-20 days combined with reduction of fertilizer use.

Ottens H.J.,Stichting Werkgroep Grauwe Kiekendief | Wiersma P.,Stichting Werkgroep Grauwe Kiekendief | Koks B.J.,Stichting Werkgroep Grauwe Kiekendief
Limosa | Year: 2013

Modern agricultural fields have little to offer for wintering birds, which has resulted in dramatic declines in numbers. Since 2008, in the provinces of Groningen and Drenthe, in the northern Netherlands, many volunteers have monitored winter birds in agricultural fields. The aim was to quantify the effect of winter food fields (WF fields), a newly introduced method of agri-environmental nature management. These 0.5 to 2 ha fields are sown with various cereals and other seed bearing plants with the aim to offer food for wintering birds such as Yellowhammer and Skylark. In 2012, 238 ha of WF fields were established in the two provinces. The number of species reported was higher in WF fields (64) than in control fields (41). Also, numbers present were much higher in WF fields than in controls (maximum numbers: 255 vs. 55). The most numerous species were Greenfinch and Yellowhammer, making up 63% of all birds. Numbers, including those of vole consumers, were highest from November to February, except for Skylark, which peaked during the migratory seasons. Bird numbers increased with WF field size but densities declined as fields became larger. Lower temperatures led to higher numbers of finches, buntings and vole eaters. Snow depth was positively correlated with number of finches, buntings, sparrows and gallinaceous birds and probably also of larks and pipits. Our results show that WF fields are of great importance to birds wintering in agricultural fields. We hypothesize that the recent increase in numbers of Yellowhammers breeding in East Groningen may have partly resulted from these management efforts. For Skylarks, however, a positive effect may be limited by the presence of shrubs and trees, which are important for most other birds.

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