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Petersen 1973. Warwick & Price 1975. Moller & Rosenberg 1983. Winther & Gray 1985. Emerson et al. 1988). although the summer weights in Massachuscits (Edward & Huebner 1977) were lower (Fig. 15). There was also a reasonable similarity in the seasonal variations in the body weight of Cerastoderma in Sweden (Moller & Rosenberg 1983). E. England (Goss-Custard et al. 1977a). S. England and Wales (Hancock & Franklin 1972. Warwick & Price 1975. Hibberi 1976. Jones 1979. Sutherland 1982a. 1982c) and the Wadden Sea (Fig. 16). Weight change and scope for growth II" Ihe negative relation between winter temperature and change in body weight (Fig. 10) is a general phenomenon, very low body weights are to be expected in southern areas during winter. The average winter sea water temperature is close to 0 °C in SW. Sweden (Moller & Rosenberg 1983), 2-4 °C in the Wadden Sea, 6-7 °C in Wales. Ireland and France and 14 °C in Portugal (Hughes 1972. Bachelet 1980. Desprez el al. 1991). Despite this large variation, there is no evidence, however, of a latitudinal variation in change in body weights during winter (Figs. 13-16). The annual variations in the weights of the soft parts of the bivalves depend on the energy budget, and thus on the balance of total energy intake and energy demands. The intake rate depends on the food consumption and thus the available food supply, while the energy demands depend primarily on ambient temperature. The decrease in body weight oi Macoma in mid summer can be explained by the decline in food supply at a time when energy demands reach a peak because of the high temperatures (Beukema et al. 1985. Hummel 1985c). The weight reduction in July may be as great as 20'i in years when the sea water temperature is between 18 and 20 °C. but with July SEASONAL VARIATION IN BODY WEIGHT OF BIVALVES 44 temperatures of 15 or 16 °C. Macoma are able to maintain iheir body weight I Beukema et al. 1985). Laboratory experiments (Hummel 1985b) confirm that a change in body weight depends on a combination of temperature and food supply. The apparent absence of a latitudinal variation in winter weight (Figs. 13 to 16) would suggest that the higher eosis of living in the more southern areas are offset by a higher fcxxl intake (and food supply) during winter. Implications for birds Winter is a difficult period for waders. Firstly, the fraction of prey which is accessible to them is (much) lower than in the summer (Zwarts & Wanink 1989). The fraction of large Scrobicularia accessible for (iv stercatcbei Haematopus ostralegus is 40% in summer but nearly i)% in winter (Zwarts & Wanink 1989 and 1991). Secondly, they have to eat more prey io compensate for the poor condition of the prey. The data summarized in this paper show dial waders have to find 1.5 to 2 times more prey in winter than in summer to maintain the same level of daily food consumption. For Scrobicularia. it has been shown that the seasonal variation in the weights of the prey actual I \ accessible to Oystercatchers is even larger, because prey within reach of the bill has less-thanaverage body weight (Zwarts & Wanink 1991). Thirdly, the energy demands of waders increase when wind forces increase and temperatures decrease: the daily food consumption of an Oystercatcher increases by 40-50%, from 30-35 to 45-50 g AFDW, as the ambient temperature drops from 10 to 0 °C (Kersten & Piersma 1987). The effect of severe winter conditions on the energy demands of ihe birds themselves is thus not fully compensated by the better body condition of the prey that results from low temperatures (Fig. 10).
Chapter 2 HOW THE FOOD SUPPLY HARVESTABLE BY WADERS IN DE WADDEN SEA DEPENDS ON THE VARIATION IN ENERGY DENSITY, BODY WEIGHT, BIOMASS, BURYING DEPTH AND BEHAVIOUR OF TIDAL-FLAT INVERTEBRATES Leo Zwarts & Jan H. Wanink published in: Neih. J. Sea Res. 11 • -141 -47611 W3 i «5
Page 1 and 2: WADERS AND THEIR ESTUARINE FOOD SUP
Page 3 and 4: plia^ohi. WADERS AND THEIR ESTUARI
Page 5 and 6: Waders and their estuarine food sup
Page 7 and 8: WADERS AND THEIR ESTUARINE FOOD SUP
Page 10 and 11: figuren: Dick Visser omslagfoto: Ja
Page 12 and 13: 15 Versatility of male curlews (Num
Page 15 and 16: That science is making progress, ma
Page 17 and 18: INTRODUCTION The remnants of brushw
Page 19 and 20: When hcnlhic bivalves extend llien
Page 21 and 22: the burrow depths and on the fracti
Page 23 and 24: INTRODUCTION Ms,i invest 409 of (he
Page 25 and 26: able lo sw itch 10 oiher prey which
Page 27 and 28: Long-term, broadly-based research c
Page 29 and 30: Chapter 1 SEASONAL VARIATION IN BOD
Page 31 and 32: SEASONAL VARIATION IN BODY WEIGHT O
Page 33 and 34: Tahle 1 Weight loss ('•- ± SE) m
Page 39 and 40: i 60 50 40 30 20 10 0 • INFESTED
Page 41 and 42: 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: SEASONAL VARIATION IN BODY WEIGHT O
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 and 94: DEPTH AND SIPHON CROPPING IN SCROBI
Page 95 and 96: Table 3. Three-Way analysis Of vari
Page 97: Chapter 4 SIPHON SIZE AND BURYING D
Page 100 and 101:
15 20 size (mm) Fig. 3. Cerasioderm
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10 size (mm) SIPHON SIZE AND DEPTH
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o, 7 01 5 | * CL 5- SIPHON SIZE AND
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4 Q) Si •a a. 16- 20- A predator:
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prey risk for an animal al a depth
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Table 6. Size al which there is a m
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* ' 1 /-/ "».-^*«C
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face and so expose themselves to a
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surface in die containers was varie
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50 OOF 310.00 I 5.00 ^ 1.00 3=" 0.5
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Tahle 1. Macoma and Scrobicularia.
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siphon would not have to reach the
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known siphon weight and burying dep
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ACCESSIBLE PREY ARE OFTEN IN POOR C
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1 2 3 4 burying depth (cm) Kin. I.
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I—1 • • : : : : ! - ! -|-r 0
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Chapter 7 DOES AN OPTIMALLY FORAGIN
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OPTIMAL FORAGING AND THE FUNCTIONAL
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100 200 300 prey density (n-m-2) Fi
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Table I. Results of five one way an
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Table 2. Results of eight iwo-wav a
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prey density II III Fig. 12. Freque
Page 147 and 148:
Page 149:
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
Page 205 and 206:
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
Page 218 and 219:
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
Page 226 and 227:
comparison between the weight of ih
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. 1', L ! •
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Introduction PREDICTING SEASONAL AN
Page 232 and 233:
PREDICTING SEASONAL AND ANNUAL FLUC
Page 234 and 235:
Page 236 and 237:
Page 238 and 239:
Page 240 and 241:
1000 r 1 II" 1 - r^Jan'80 PREDICTIN
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Page 244 and 245:
Page 246 and 247:
Page 248 and 249:
Page 250 and 251:
Page 252 and 253:
IOO BO 60 40 20 0 PREDICTING SEASON
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Page 256 and 257:
Page 258 and 259:
Page 260 and 261:
Page 262 and 263:
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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
Page 281 and 282:
WHY KNOT TAKE MEDIUM-SIZED MACOMA T
Page 283 and 284:
Chapter 13 ANNUAL AND SEASONAL VARI
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VARIATION IN FOOD SUPPLY OF KNOT AN
Page 287 and 288:
Two sites (N and M in Fig. 2) were
Page 289 and 290:
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
Page 297 and 298:
Chapter 14 SEASONAL TREND IN BURROW
Page 299 and 300:
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
Page 307 and 308:
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
Page 331 and 332:
PREY DEPLETION BY OYSTERCATCHER AND
Page 333 and 334:
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
Page 341 and 342:
SAMENVATTING 345
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Voorgeschiedenis In 1960 verscheen
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maken. Als gebied A een grotere voe
Page 347 and 348:
omdat ze nog vrijwel niets wegen. l
Page 349 and 350:
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
Page 363 and 364:
REFERENCES 367
Page 365 and 366:
Allen RL. 1983. Feeding behaviour o
Page 367 and 368:
BreyT. 1989. Der Einfluss physikali
Page 369 and 370:
latie tol chironoiiiiilen en de wai
Page 371 and 372:
huch der Vogel Milteleuropas, Band
Page 373 and 374:
llolmann II. & H. Huerschelmann 196
Page 375 and 376:
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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