OTTENS HJ, KUIPER MW, SCHARENBURG CWM & KOKS BJ (2013) Field margins are not the key to success for the Skylark Alauda arvensis; a case study in Eastern Groningen, The Netherlands. LIMOSA 86 (3): 140-152.

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.

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