Grassland management suitable for Black-tailed Godwits is rare in The Netherlands

Posted on: 2023-01-25 10:04:39

Yuhong Li, Theunis Piersma, Jos Hooijmeijer, and Ruth Howison

The majority of Dutch grasslands are not suitable for our national bird, the Black-tailed Godwit, as a result of high management intensity. In areas with intensive agriculture, Godwits need more space to meet all their resource needs (Fig. 1). Yuhong Li and fellow researchers from the University of Groningen (GELIFES) draw these conclusions in a study published in the journal Ecological Solutions and Evidence on 6th January 2023.

Figure 1: Median land-use intensity index of the surroundings of their nests in relation to breeding core range size of the tracked godwits. With increasing land-use intensity, MCP (minimum convex polygon) core range size increased strongly, meaning that Godwits breeding in more intensive agricultural land need more space.

The researchers made a map of the intensity of agricultural land use of the entire Netherlands using radar satellite images. They analysed which sites were visited by 57 Godwits that received a satellite transmitter between 2013 and 2019. By linking the locations of the Godwits to the intensity of agricultural land use, they found that the habitats selected by the breeding Godwits had a much lower intensity of management on a regional and national scale than conventional grasslands. As much as 94% of Dutch grassland is so intensively managed that it is unsuitable for Black-tailed Godwits to breed there.

Moreover, this study shows that Godwits breeding on agricultural land with higher intensity of use, tend to use a larger territory. This means that Godwits in intensively managed areas need to search larger areas for food than in areas managed at lower intensities, which might increase the risk of exposing young chicks to predation in their absence.

Research on a national scale
Godwits often return to the same site to breed from year to year. To avoid tracking only Godwits from known, good breeding sites, we tagged 37 birds during spring migration in Spain and Portugal. So far, only local-scale studies on habitat choice of Black-tailed Godwit have been conducted. In this study, following these 37 Godwits with unknown breeding sites, we were able to determine site choice on a national scale for the first time and find that the intensity of use of most of the Dutch grassland is reason for Godwits to avoid those areas.

Call for habitat restoration at landscape scale
This study shows how a high use intensity of grasslands associated with lowered groundwater levels, extensive mechanisation and the use of chemical pesticides has produced a landscape in which Godwits no longer occur or require a larger territory to meet their resource needs. This currently limits opportunities for population recovery. Godwits are an indicator species for healthy grassland ecosystems with good baseline nature quality, as their presence is linked to the availability of soil fauna, insects and diverse vegetation structure. Landscape planning should therefore focus on larger grassland bird core areas with such qualities to improve the conservation status of Godwits.

Figure 2: (A) map showing land use intensity across the country (based on Radar Sentinel-1) with the locations of the 57 Black-tailed Godwits monitored (in different colours). (B) A Black-tailed Godwit perched on a fence post. Image credits: Map by Yuhong Li, photo by Ruth Howison

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