Transcript Hooge Platen Nature Reserve Bird island in a shipping channel

Hooge Platen Nature Reserve
Bird island in a shipping channel
November 13th-17th, Minsmere, Suffolk
Rene Beijersbergen
Westerscheld estuary
Keeping an eye on the island
Volunteers at work
Little Tern breeding in the “safe
haven”…
Behind the “seawall”……..
The beach, the seawall and the dunes
Vegetation of annuals
Waterdunen on the estuary
Terns breeding on artificial sites
Pionieers Hooge Platen
breeding pairs (n)
300
200
100
0
1978
1984
1990
Little tern
1996
Avocet
2002
Kentish plover
2008
2012
Population development of of gulls and terns
8000
4000
0
1982
1986
1990
Common tern
1994
Sandwich tern
1998
Blackheaded gull
2002
Mediterrenean gull
2008
2012
Breeding pairs and success of Sandwich tern
6000
1,2
4000
0,8
2000
0,4
0
0
1987
1989
1991
1993
1995
1997
broedparen (n)
1999
2001
2003
2005
broedsucces (juv/paar)
2007
2009
2011
Prey items fed to the chicks (left) and partners on the
breeding site in three species of terns in the same
period.
100
75
50
25
0
Little tern
Common tern
sandeel
Sanwich tern
herring
Terns feed mainly on two species of fish
Sandeel
•
•
•
•
Bottomdweller
Poor swimmer
Local
Year round
• Live in shallow water (-20 m)
• Young and adult share
partly same feeding ares
Herring
•
•
•
•
From surface to bottom
Fast swimmer
Migrator
Young and subadults near
coast from may-august
• Spawning area and nursery
geographical separated
• Adults live from the Channel
till the Norwegian coast
Years of poor reproduction by lack of food:
• Bodyweight of chicks
does not increase over
days
• Chicks die of starvation
• Both parents go out
fishing
• Increase of predation
So what can we conclude…..
• Feeding sites are getting more and more unpredictable
when the function as a nursery for sandeel and herring is
becoming less
• Breeding sites (Waterdunen & Zwin) are better off on close
distance of nurseries and other spots where small fish
aggregrates
• Terns are dependant on small fish for the young chicks and
bigger fish for themselves
• The days when producing a clutch and the first days after
hatching seems to be the most vulnerable days.