Mortality of Black-tailed Godwit Limosa limosa and Northern Lapwing Vanellus vanellus chicks in wet grasslands: influence of predation and agriculture |
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Authors: | Hans Schekkerman Wolf Teunissen and Ernst Oosterveld |
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Institution: | (1) Dutch Centre for Avian Migration and Demography, Netherlands Institute of Ecology (NIOO-KNAW), P.O. Box 40, 6666 ZG Heteren, The Netherlands;(2) Alterra, Wageningen University and Research Centre, Wageningen, The Netherlands;(3) Animal Ecology Group, Centre for Ecological and Evolutionary Studies, University of Groningen, Groningen, The Netherlands;(4) SOVON Dutch Centre for Field Ornithology, Rijksstraatweg 178, 6573 DG Beek-Ubbergen, The Netherlands;(5) Altenburg and Wymenga Ecological Consultants, P.O. Box 32, 9269 ZR Veenwouden, The Netherlands |
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Abstract: | Grassland-breeding shorebirds show widespread declines due to a reduction in breeding productivity following agricultural
intensification. However, there is also concern that increasing predation causes further declines or precludes population
recovery. Predation may itself be enhanced by agriculture through changes in habitat or food availability, but little is known
about the mortality of nidifugous shorebird chicks. We studied mortality by radio-tagging 662 chicks of Black-tailed Godwit
Limosa limosa and Northern Lapwing Vanellus vanellus in 15 farmland sites in the Netherlands. Tagging and handling had no effect on the condition and survival of godwit chicks,
but body condition was reduced by 6–11% in lapwing chicks wearing a tag for longer than 3 days. Fledging success was 0–24%
in both species. Mortality was highest in young chicks but remained considerable until after fledging. Losses were traced
mostly to predators (70–85%; 15 species, predominantly birds), but at least 5–10% were due to mowing, and 10–20% were due
to other causes, including entrapment in ditches and starvation. Chicks staying in fields that were cut before the next radio
check were found much more often as mowing victims and somewhat more often as prey remains than chicks in fields not cut,
indicating that predation includes a limited amount of scavenging. The predation hazard for godwit chicks was higher in recently
cut or grazed fields than in the tall, uncut grasslands they preferred, while that for lapwing chicks was lowest in grazed
fields. In godwit chicks, poor body condition increased mortality risk, not only from starvation but also from other causes.
Predation on godwit chicks was thus enhanced by intensive farming through a decline in the availability of cover, augmented
by a reduced body condition, possibly due to food availability problems. Changes in farming practice may therefore help reduce
predation pressure, though the observed interactions explained only part of the high predation rate in godwits and none in
lapwings. Predator abundance has increased in Dutch wet grassland regions, and chick predation has become a factor that should
be considered in planning the type and location of conservation measures. |
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Keywords: | Agricultural intensification Chick survival Condition Predation Shorebirds |
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