food and feeding of little tern on the hooge platen
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Food and feeding of Little Tern on the Hooge Platen. November 16th 2012, Minsmere, Suffolk Rene Beijersbergen. Distribution and population. Coastal breeders : Common tern , Little tern and Kentish plover. In this contribution on Little Tern little attention for …. Floodings - PowerPoint PPT PresentationTRANSCRIPT
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Food and feeding of Little Tern on the Hooge Platen
November 16th 2012, Minsmere, SuffolkRene Beijersbergen
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Distribution and population
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Coastal breeders: Common tern, Little tern and Kentish plover
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In this contribution on Little Tern little attention for….
FloodingsHabitatselectionDevelopment of vegetationCompetitionPredation
But I like to focus on food and feeding.
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Breeding and feeding within short range
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april (n=6) may (n=363)
june (n=167)
juli (n=139)0
50
100
sand eel herring
Little tern’s prey
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Distribution of clutchsize of Little tern
0
25
50
n=138
n cl
utch
es (%
)
clutch of 3 2 1
Start of laying, clutchsize and weight in Little tern
0
14
28
150 170day (may 31st = day 151)
weig
ht o
f clu
tch
(g)
clutch 3 2 1
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1993 20060
40
80
120
160
Change in search time, diving success and clutch weight
searchtime (s) divingsuccess (%)clutchweight (g)
inde
x (1
993
= (1
00)
Fish intake and clutch weight
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Clutch size in the period 1990 – 2010 was between 1.78 and 2.82
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4 6 11 13 15 18 21 23 260
25
50
75
100
Arrival, food and settlement of Little Tern
resting (n) pairs courtshippingpairs breeding n dives x10 (100 s searchtime)
may
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2 3 5 5.80
25
50
75
100
Succesfull dives (%) in relation to number of dives (n/100 s search time) for Sandeel
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Breeding between 2002 and 2010
Hooge Platen• Start egg laying between
May 3rd and June 4th• Average date May 19th
• Number of breeding pairs between 0 – 250
• Average 112 pairs
Foreshore• Start egg laying between
May 4th and May 25th• Average date May 14th
• Number of breeding pairs between 0 – 120
• Average 36 pairs
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0
2
4
6
8
Weight of fish (sandeel or herring) caught in the striped zone
Foreshore Bol
wei
ght (
g/10
0 s
sear
ch ti
me
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Litle terns have no choice but to breed close to the feeding site
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Are (Little) terns flexible when food is scarce……?
• They are flexible in the clutchsize
• They are flexible in the start of egg laying
• They are flexible in choosing a breedingsite
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Number of breeding pairs of Little tern on the Hoge Platen Nature Reserve
0
50
100
150
200
250
1978 1984 1990 1996 2002 2008 2012
Little Tern Lineair (Little Tern)
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Sandeel becomes less abundant…
1985-1991 (n=1286)
1992-1998 (n=507)
1999-2005 (n=614)
20006-2012 (n=2088)
0
20
40
60
80
Preyspecies of Little Tern in four 7-years periods between 1985 - 2012
Sandeel Herring
(%)
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Around the North Sea Sandeel becomes less abundant….
• Global warming and climate change
• Industrial fisheries
• Local dredging of harbours and shipping channels
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So what can we conclude…..• For succesfull breeding Little Tern seems to be dependant on
both 0-year Sandeel and Herring
• During pre-breeding, egg laying and breeding they depend mainly on Sandeel
• Number of breeding pairs, clutchsize and site depend on the availability of Sandeel
• Terns are dependant on small fish for the young chicks and bigger fish for themselves
• On the continent the largest colonies we find close to the seashore