waders and their estuarine food supplies - Vlaams Instituut voor de ...

The measurements of handling time in the live prev
species are summarized in Fig. 9. Only times when
prey were successfully taken are shown. Handling
times for Mussels are for stabbing Oystercatchers. Depending
on the prey si/e. n takes an Oystercatcher 3 lo
300 s to open and eat the llesh in a bivalve. The flesh
weight increases from 5 mg to over 10()0 mg over the
range of size classes studied. In all prey species, flesh
weight increases exponentially with size, with an exponent
of about 3. Handling time is also an exponential
PREY SIZE SELECTION AND INTAKE RATE
function of prey size, but the exponent is much lower
(Fig. 9).
Dividing prey weight by handling time gives the
profitability, i.e. the intake rate in mg dry flesh s" 1
while handling the prey (Fig. 10). When all data are
lumped, profitability is more variable than handling
time. This is due to the considerable variation in the
flesh content of Ihe prey; for instance, in Scrobicularia
and Cerastoderma. winter weight is almost half that in
early summer (Zwarts 1991). But. despite this, there is
- Cerastoderma
y=0J22x»l.94
|- p< 0.001
p-0.70
12 14 16 18 20 15 20 25 30 35 40 10 20 30 40
?36 Mya .
L y>0 76x-8.33
p< 0.001
5 32 h r«0.82
03
"5
5-28
24
20-
16
12
8
4
0
-INTAKE RATE.
Mytilus
I y=0.30x-4.32
p