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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