Nest predation and trampling as management risks in grazed coastal meadows |
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Authors: | Veli-Matti Pakanen Aappo Luukkonen Kari Koivula |
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Institution: | (1) Department of Biology, University of Oulu, P. O. Box 3000, 90014 Oulu, Finland |
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Abstract: | Livestock grazing is an important management tool of agri-environment schemes initiated within the European Union to maintain
and restore biodiversity of grassland birds. However, grazing can affect bird populations negatively by depressing reproduction
through nest trampling and increasing nest predation. These effects are, however, considered low when using recommended stocking
rates. By simulating wader nests, we experimentally quantify and examine the causes of variation in trampling rates on managed
Baltic coastal meadows. Secondly, we examine whether livestock presence increases nest predation of one management target,
the critically endangered southern dunlin (Calidris alpina schinzii). Trampling rates of experimental nests were high. Only 21% of nests would have survived a three week incubating period early
in the grazing season. Trampling rates were most severe at the onset of grazing and decreased with time. Thus, timing of grazing
plays a crucial role in determining breeding success on managed meadows. Predation rates of dunlin nests were moderate and
did not depend on livestock presence suggesting that incubating dunlin are not disturbed by cattle. While grazing is vital
in habitat restoration and in conserving grassland biodiversity, our results suggest that grazing may also threaten the viability
of populations if negative effects are underestimated. Therefore, management plans, especially for endangered species, should
not only rely on general recommendations on stocking rates but instead planners need to evaluate the significance of negative
effects in terms of local conditions (timing of breeding and grazing, space use of cattle and birds, measured trampling rates)
and adjust grazing practises accordingly. |
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