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0 1 2k 1f S 3- -C "Or •S 4- O) c "£• 5- 7- 5 10 amount of siphon cut (mg) DEPTH AND SIPHON CROPPING IN SCROBICULARIA REMAINING • 4- 6mg D 7- 9mg • 10-I2mg 0 13-1Smg A I6-I8mg Fig. 6. The depth of animals (37 to 38 nun) as a function of the amount of siphon removed, given for live categories isee key I based on the weight ol the remaining siphon; the results ol an analysis ol variance are given in Table 2. Table 2. Three-way analysis of variance '
Table 3. Three-Way analysis Of variance to lest the effect of the weight ol ihe total siphon (4-6, ...22-24 mg), ihe experimental conditions (0. 1-9. 10-15 mg removed), and time (Day 0... 5) on the dry weighl ol the body In = 911: see also Fig. 7. DEPTH AND SIPHON CROPPING IN SCROBICULARIA R\ • 1 P (a) Siphon weighl 26.7 0.001 (b) Exp. condition 6.4 0.026 (c) Time 4.1 0.435 (aix(bi 1 1 (I.S47 (ai xici 4.3 0.977 (b) > 3.2 0.433 Table 3). The animals losing < 9 mg were pooled be cause the regression of body weight on siphon weight was the same. The body weight was relatively low, however, in the bivalves from which > 10 mg of the siphon was removed. All animals were alive when they were dug up 1 to 5 days after the siphon had been removed. These results agree with the data collected by Hodgson (1982a) who showed thai the energetic cost of regeneration was low when 15% ot me siphon was removed but when 5(W< of more was cut off. regeneration took place at the expense of the body condition. Some animals in his experiment died, but no information is given about survival and siphon loss. n= 2 5 4 6 1 1 '00 30 €• 60 survival 20 0 • i 5 . ,i 10 15 i 20 amount of siphon cut (mg) Fig. 8. Survival of Scrobicularia (37 mm) kept 2 weeks in an aquarium, in relation to the amounl of ihe siphon removed I after Straal. Wanink & Zwarts unpubl. dala). 91 Direct evidence on the effect of siphon amputation on subsequent survival is available from an experiment where Scrobicularia were held in a small aquarium filled with 20 em mud and sea water for 14 days, without providing food. All animals from which 13 to 19 mg of the siphon weight has been removed w ere moribund or dead, whilst all animals remained in perfect condition when 0 to 6 mg was taken (Fig. 8). Siphon weight, burying depth and feeding range The relationship between depth and siphon weight (Fig. 9A. redrawn from Fig. 5). can be used to calculate the weight per cm of siphon from the upper edge of the shell to the surface, assuming that Scrobicularia have to reach the surface (Fig. 9B). It shows that freeliving animals with a large siphon live at a depth that allows them 3 mg per cm. Of more interest is the minimum value: animals with a short siphon, although they minimize the distance to the surface, only have available about I mg per cm. Assuming that the maximum a feeding siphon can be stretched is 1 or 1.5 mg per cm. it is possible to estimate the potential reach of the inhalant siphon during surface feeding (Fig. 9C). Linke (1939). Green (1967. 1968). and Hughes (1969) have given extensive descriptions of the feeding behaviour of Scrobicularia. but more detailed research is necessary to confirm that the range on the surface over which the animals can reach really depends on siphon weight and burying depth, as depicted in Fig. 9C. The model presented in Fig. 9 can. however, be used to derive some predictions. One prediction is that about half the population will feed within a radius of 5 to 10 cm around the burrow. This can be measured directly, but can also be derived from the length of the starlike feeding tracks which a Scrobicularia makes during the sucking of the substratum. The predicted mean value of 5 to 10 cm agrees well with observations of a normal feeding range of 3 lo 10 cm (Thamdrup 1935), 4 to 10 cm (Linke 1939) and 5 to 8 cm (Hughes 1969). The maximum feeding range of 20 cm (Linke 1939) falls just within the predicted range (Fig. 9C I, It is also to be expected that animals possessing a heavier siphon and thus a larger feeding space, are in a better condition than animals with a short siphon. This was indeed the case in the experimental animals (Fig. 7) as well as in nature: the body weight is 2(1 to 30'-'}
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WADERS AND THEIR ESTUARINE FOOD SUP
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plia^ohi. WADERS AND THEIR ESTUARI
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Waders and their estuarine food sup
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WADERS AND THEIR ESTUARINE FOOD SUP
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figuren: Dick Visser omslagfoto: Ja
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15 Versatility of male curlews (Num
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That science is making progress, ma
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INTRODUCTION The remnants of brushw
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When hcnlhic bivalves extend llien
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the burrow depths and on the fracti
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INTRODUCTION Ms,i invest 409 of (he
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able lo sw itch 10 oiher prey which
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Long-term, broadly-based research c
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Chapter 1 SEASONAL VARIATION IN BOD
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SEASONAL VARIATION IN BODY WEIGHT O
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Tahle 1 Weight loss ('•- ± SE) m
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i 60 50 40 30 20 10 0 • INFESTED
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240- SEASONAL VARIATION IN BODY WEI
Page 43 and 44: 20 10 0 -10 -20h 2 3 4 5 6 7 8 9 se
Page 45 and 46: a E 400 - S. plana 35 mm 320 240 16
Page 47 and 48: SEASONAL VARIATION IN BODY WEIGHT O
Page 49 and 50: Chapter 2 HOW THE FOOD SUPPLY HARVE
Page 51 and 52: FOOD SUPPLY HARVESTABLE BY WADERS H
Page 53 and 54: Methods The study sites were situat
Page 55 and 56: less than that of bivalves, partly
Page 57 and 58: I Fig. 3). Peak condition was reach
Page 59 and 60: total biomass since most of those t
Page 61 and 62: on the basis of the preceding and t
Page 63 and 64: However, for obvious reasons, we ma
Page 65 and 66: prey. A decrease in the prey densit
Page 67 and 68: Tahle 2. The intake rate ol < lyste
Page 69 and 70: * ' % -. . ; a X - . - * • ^ •
Page 71 and 72: (Zwarts & Wanink 1989). In quiet we
Page 73 and 74: general law relating handling time
Page 75 and 76: nearly twice as much time (0.79 s).
Page 77 and 78: 4 5 6 7 8 9 size class of Corophium
Page 79 and 80: and annually. Second, the lower siz
Page 81 and 82: Prey switching Waders feeding on ti
Page 83 and 84: autumn and spring, and the contrary
Page 85 and 86: where they switch to surface-living
Page 87 and 88: Chapter 3 BURYING DEPTH OF THE BENT
Page 89 and 90: DEPTH AND SIPHON CROPPING IN SCROBI
Page 91 and 92: I DEPTH AND SIPHON CROPPING IN SCRO
Page 93: DEPTH AND SIPHON CROPPING IN SCROBI
Page 97: Chapter 4 SIPHON SIZE AND BURYING D
Page 100 and 101: 15 20 size (mm) Fig. 3. Cerasioderm
Page 102 and 103: 10 size (mm) SIPHON SIZE AND DEPTH
Page 104 and 105: o, 7 01 5 | * CL 5- SIPHON SIZE AND
Page 106 and 107: 4 Q) Si •a a. 16- 20- A predator:
Page 108 and 109: prey risk for an animal al a depth
Page 110 and 111: Table 6. Size al which there is a m
Page 112 and 113: * ' 1 /-/ "».-^*«C
Page 114 and 115: face and so expose themselves to a
Page 116 and 117: surface in die containers was varie
Page 118 and 119: 50 OOF 310.00 I 5.00 ^ 1.00 3=" 0.5
Page 120 and 121: Tahle 1. Macoma and Scrobicularia.
Page 122 and 123: siphon would not have to reach the
Page 124 and 125: known siphon weight and burying dep
Page 127 and 128: ACCESSIBLE PREY ARE OFTEN IN POOR C
Page 129 and 130: 1 2 3 4 burying depth (cm) Kin. I.
Page 131 and 132: I—1 • • : : : : ! - ! -|-r 0
Page 133 and 134: Chapter 7 DOES AN OPTIMALLY FORAGIN
Page 135 and 136: OPTIMAL FORAGING AND THE FUNCTIONAL
Page 137 and 138: 100 200 300 prey density (n-m-2) Fi
Page 139 and 140: Table I. Results of five one way an
Page 141 and 142: Table 2. Results of eight iwo-wav a
Page 143 and 144: OPTIMAL FORAGING AND THE FUNCTIONAL
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prey density II III Fig. 12. Freque
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OPTIMAL FORAGING AND THE FUNCTIONAL
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PREY SIZE SELECTION AND INTAKE RATE
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Predicted 'passive size selection'
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lig. 2. Larger Mussels are less ava
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Fig. 5. Scrobicularia plana. Size c
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and maiiv are too thick-shelled to
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The measurements of handling time i
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1 2 3 4 5 6 7 probing depth (cm PRE
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valves may vary by a factor of two
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optimal foraging model, the minimum
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their gut is full? Do they reduce t
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PREY PROFITABILITY AND INTAKE RATE
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catchers to take only certain prey
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licult error of estimate arose if p
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Counts of feeding and non-feeding b
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20 30 40 50 shell length (mm) PREY
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Nereis Arenicola tipuia earthwo'm M
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take rate. We might therefore expec
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prey species, using parallel slopes
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5.0 4.0 1-3.0 a & • % * • * •
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time during the feeding period. As
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winter. Similarly, handling time in
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5.0 - f-4.0 S 3.0 in I 20 a 2 a | 1
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situation arrived in the western pa
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• ' • 14 PREY PROFITABILITY AND
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Notes lo appendix: PREY PROFITABILI
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Chapter 10 WHY OYSTERCATCHERS HAEMA
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2 4 6 8 10 time on feeding area (h)
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80- 60- o 80 60- 40- 20- INTAKE RAT
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est of bod\ behind: an estimated 22
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INTAKE RATE AND PROCESSING RATE IN
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Wanink 1993). The energy content of
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(7) Age All studies dealt with adul
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irds over long periods. As an examp
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Discussion There is no difference i
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comparison between the weight of ih
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. 1', L ! •
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Introduction PREDICTING SEASONAL AN
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PREDICTING SEASONAL AND ANNUAL FLUC
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1000 r 1 II" 1 - r^Jan'80 PREDICTIN
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IOO BO 60 40 20 0 PREDICTING SEASON
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WHY KNOT TAKE MEDIUM-SIZED MACOMA W
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in Zwarts & Esselink 1989). The len
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shell length (mm) FIR. 3. Peringia.
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fused, specimens larger than this w
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50 100- s s I — f = S. plana, n=2
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area is twice as large as the touch
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10 15 lower size threshold (mm) Fig
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lime (Hughes 1979). This would furt
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WHY KNOT TAKE MEDIUM-SIZED MACOMA T
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Chapter 13 ANNUAL AND SEASONAL VARI
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VARIATION IN FOOD SUPPLY OF KNOT AN
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Two sites (N and M in Fig. 2) were
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20 30 VARIATION IN FOOD SUPPLY OF K
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20 l i r'l ' i •o j^y^T n ^ ' " ^
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July ' Aug ' Sept Fig. 9. Proportio
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available. There must, however, be
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Chapter 14 SEASONAL TREND IN BURROW
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BURROWING AND FEEDING IN NEREIS SEA
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Table 2. Results of a 2-way analysi
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June 1981 June 1982 is * N.MUD •
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8 10 I 12 JZ 5. -g 1*» •e o i 16
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6 - n=!080 5 • g 4 CP > i 3 CO CD
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1985) and Curlew (/wails ,v, Lsseli
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Chapter 15 VERSATILITY OF MALE CURL
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Smid! 1951. Muus 1967, Wolff 1973,
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0.6 0.8 1.0 1.2 1.4 1.6 jaw lengih
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Na oi both Nrieck Fig. 7. Numenius
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6 8 10 12 14 16 18 worm length (cm)
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too (Fig. 11 A). Indeed, the averag
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VERSATILITY OF CURLEWS FEEDING ON N
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total time spent al the surface. Th
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2 4 . • 2.2 • 30 .-.2.0 to Q. 1
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PREY DEPLETION BY OYSTERCATCHER AND
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the rule: the observed lower limit
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to locate the clams after they had
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Curlew, by bury ing some hundreds o
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PREY DEPLETION BY OYSTERCATCHER AND
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SAMENVATTING 345
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Voorgeschiedenis In 1960 verscheen
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maken. Als gebied A een grotere voe
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omdat ze nog vrijwel niets wegen. l
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kunnen opzuigen. of diep leven en z
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van de uitgerekte sifo over het wad
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het toen niet gemakkelijk hebben ge
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doende nonnetjes van 10 tot 15 mm l
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aangevoerde voedsel en de wulp past
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zijn dan twee jaar en wulpen geen s
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was dan ook dank/ij de inzet van al
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REFERENCES 367
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Allen RL. 1983. Feeding behaviour o
Page 367 and 368:
BreyT. 1989. Der Einfluss physikali
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latie tol chironoiiiiilen en de wai
Page 371 and 372:
huch der Vogel Milteleuropas, Band
Page 373 and 374:
llolmann II. & H. Huerschelmann 196
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l-cndrem D.W. 1984. Flocking, feedi
Page 377 and 378:
Pekkarinen M. 1984. Regeneration of
Page 379 and 380:
lion of Mussels Mytilus edulis hy O
Page 381 and 382:
lulal Dal esiuanes: a comparison of
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