Food and feeding of Little Tern on the Hooge Platen

November 16th 2012, Minsmere, SuffolkRene Beijersbergen

Distribution and population

Coastal breeders: Common tern, Little tern and Kentish plover

In this contribution on Little Tern little attention for….

FloodingsHabitatselectionDevelopment of vegetationCompetitionPredation

But I like to focus on food and feeding.

Breeding and feeding within short range

april (n=6) may (n=363)

june (n=167)

juli (n=139)0

50

100

sand eel herring

Little tern’s prey

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

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

Clutch size in the period 1990 – 2010 was between 1.78 and 2.82

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

2 3 5 5.80

25

50

75

100

Succesfull dives (%) in relation to number of dives (n/100 s search time) for Sandeel

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

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

Litle terns have no choice but to breed close to the feeding site

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

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)

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

(%)

Around the North Sea Sandeel becomes less abundant….

• Global warming and climate change

• Industrial fisheries

• Local dredging of harbours and shipping channels

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