Foto: Peter Teune
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OTTENS HJ, WIERSMA P, KUSTERS T & DIJKSTRA B (2021) Electric fencing of nests and radio tracking of chicks provide clues for the protection of Eurasian Curlews Numenius arquata in the province of Drenthe. LIMOSA 94 (1): 30-42.

Dutch breeding numbers of Eurasian Curlew have declined significantly in the last two decades. Because low chick survival is suggested to be a major cause of the species' decline, we protected nests in agricultural fields in the province of Drenthe against predation using electrical fences in 2018-19 and tracked chicks using radio-transmitters in 2019 to study their survival and habitat use. As predicted, fencing greatly improved nest success. Although hatching success can be improved by fencing nests, reproduction often still fails due to high chick mortality. A total of 39 nests were protected, when clutches were complete, using electrical fencing of 10 × 10 m. Another 39 nests served as controls but were still protected against agricultural activities by marking (Tab. 1). In 2019, 25 chicks were equipped with radio transmitters and tracked every 2-4 days, at which time body mass and biometry were measured and the habitat determined. When 35 days old, a chick was considered to have successfully fledged. Of protected nests, 71% and 72% hatched eggs, while 7% and 33% of unprotected nests hatched eggs in 2018 and 2019, respectively (Fig. 2). Around 54% of clutches failed due to predation and four marked, but unprotected nests failed due to agricultural activities. Protected and unprotected nests produced 2.28 and 0.96 hatchlings per nest, respectively. 58% of chicks equipped with radio-transmitters when one day old died within a week and 11% reached fledging age (Fig. 3). Curlew families quickly left arable land for pastures, with a preference for extensively managed pastures (Fig. 5). There were no differences in development of mass, bill length and wing length of chicks between preferred habitats (Fig. 7, Tab.2). Current agri-environment schemes in Drenthe are not suited for the protection of Eurasian Curlews. Potential protection measures could include extensification of grassland and crop management, and electric fencing of entire fields to protect against mammalian predators.

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limosa 94.1 2021
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