Niels Martin Schmidt Impacts of wet grassland management and winter severity on wader breeding...
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Niels Martin Schmidt Impacts of wet grassland management and winter severity on wader breeding numbers in Eastern Denmark
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Transcript of Niels Martin Schmidt Impacts of wet grassland management and winter severity on wader breeding...
Niels Martin Schmidt
Impacts of wet grassland management and winter severity on wader breeding numbers in
Eastern Denmark
Wader population development• Most wader populations are declining in Denmark,
and in Europe in general
From Jacobsen (2000)
Index of lapwing breeding in Denmark
0
10
20
30
40
50
60
70
80
90
100
19
76
19
77
19
78
19
79
19
80
19
81
19
82
19
83
19
84
19
85
19
86
19
87
19
88
19
89
19
90
19
91
19
92
19
93
19
94
19
95
19
96
19
97
19
98
19
99
Bre
ed
ing
in
de
x
Wader population conservation• Large efforts are being invested in reversing this
trend
=> mainly focused on wet grassland management
• Waders also respond strongly to winter severity
• Relative importance of grassland management and winter severity
The Klydesø reserve• Area of national interest as wader breeding ground
Lapwing Redshank Avocet Ringed plover Oystercatcher
• Reclaimed from sea in 1945=> Situated below sea-level=> Large succesional changes=> Detoriation of costal meadow as wader
breeding ground
Population development in the Klydesø reserve
0
10
20
30
40
50
60
70
80
1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001
Bre
edin
g p
airs
Lapwing Redshank Oystercatcher Avocet Ringed Plover
Grazing Winter flooding
Management implements• Cattle grazing (app. one steer per ha, 38 - 270 ha)
• Winter flooding (app. 115 ha shallow water)
Expected effects = more breeding and foraging habitats
• Fox exclusion
Expected effect = less predation on nests
Winter severity• Proxy of winter severity: NAO winter state
Expected effects of mild winters (high NAO)
• Improved survival when migrating and when on winter grounds
• Early onset of breeding in years following mild winters
• Changes in food availability on tidal flats
Population models• Autoregressive analyses• Most parsimonoius model selected by AICc
Nt = Nt-1 Nt-2 GRAZING WINTER-FLOODING NAO
Waders, management and climate
Nt-1 Nt-2 NAOt GRt-1 WFt R2
Lapwing ++ 0.80
Redshank ++ 0.62
Avocet -- ++ 0.82
Ringed plover - + 0.88
Oystercatcher + - 0.62
Lapwings and winter severity
Nt-1 Nt-2 NAOt GRt-1 WFt R2
Lapwing
(Klydesø)++ 0.80
Lapwing (Tipperne)
++ 0.63
Conclusions• Management implements did result in increased
(most) wader breeding pairs
• Multi-lateral conservation approach needed for ensure coastal meadow species diversity
• Winter severity may be more important when management effort is constant
The Lapwing paradox
• High predation pressure on nests (c. 90%)=> too low production of young to maintain
population size
0
10
20
30
40
50
60
70
80
1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001
Bre
edin
g p
airs
• Where do the lapwings come from?
The Lapwing paradox
• Underestimation of production of young?• Attract birds from other (declining) population?• Production of young in arable areas, e.g. cereals?
