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

component of the handling time, depends on the number
of catch and throw movements made. For instance,
the time required by a Common Sandpiper to sw allow
a ehironomid larva increased from 0.32 lo 1. 12 s if the
number of such movements increased from 1 to 10.
This species needed 0.43 s and 2.11 catch and throw
movements, on average, to transport a ehironomid
from bill tip to gape. It (ook a Black-tailed Godwit
Kin. 12. The nine needed io eat a small pre) us a liinciinnol A. body
weight und B. hill length Ol birds. As ihe limes needed to eut small
prev were calculated Irom the feeding rate (prey per unil lime
feeding) when small prey were taken in a high rale and the search
lime approaches zero, we use the term 'composue handling time' to
distinguish it from directly measured 'handling limes' Ihe composite
handling time was determined in two ways It {requeue*/
distributions ol composite handling times were available, we used
ihe average ol the shortest 2V < i study • no. I lo 9 and I 11. Ill uil othei
cases, we look the lowest average Composite handling nine per day.
month, /one or experimental condition. All data were collected in
ihe field, but Stud) RO, 5, 12. 13 and 17 were done in the laboratory
I "ot .idiili VvocetS .in adjustmenl of bill length has been undertaken,
since Ihey touch Nereis al a point about 3/4 along the hill when ilicy
sweep the bill through die mud: no adjustment was necessary Im
juvenile Avocets as they pecked Comphium from the surface with
the tips of their bill. The multiple regression equalion is given in
panel B. Further explanation in text.
no bird species prev
FOOD SUPPLY HARVESTABLE BY WADERS
f 00 o
c
ra
S '-8
a 1-6
E
R 1.4
1 2
1 0
0 B
0.6I-
0.4-
0.2-
0.0
ii"-
300 400 500 600 700
body weight (g)
y=0 44+0.013MI-0 OOWweighl
20 40 60 80 100
bill length (mm)
I Glossy Ibis (nihil ula fliiiniiialis v an der Kamp & Zwarts unpubl.
2 Black-tailed Godwit rice grain Zwarts unpubl.
3 Black-tailed Godwit ('orbicnla llitminiiti.s v an der Kamp & Zwarts unpubl
4 Black-tailed Godwit ehironomid larvae Dirkscn .••