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

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$Wetenschap - \Nijverheid- Handel$

1400 1200 - • OD A A Great Britain •31000 / JH f 800 f >. 800 >. 0 600 £ A—1\ Wadden_/ / ^*-»^\ Sea/ / Ul «- 400 ZOO V Moreeambe Bay 1 / / ICatlewaier I',7:W.]3.-UJI V FOOD SUPPLY HARVESTABLE BY WADERS Tne Nelheilands Exer . /m iConwy \ Eastern Scheldl|\ , sj-^^ ILynher^. 0 —1 1 1 1 1 1 . J 1 1 1 1 L_ J F M A M J J A S O N D Fig. 18. Variation in body weight (AFDW. mg) of Mytilus eduli.s 50 mm long 111 seven areas. Sources: Exe (Cayford & Goss-Custard 1990). Conwy (Dare & Edwards 1975: averages lor three years), Moreeambe Bay (Dare 197?; average- Im three years; inrmiM! has been made fot weight loss due 10 formalin (12.8%); the paper gives DW; these were converted into AFDW. assuming thai ash content is li'.i); Eastern Scheldt (Craeymeersch et al. 19X6; corrected for weigh) loss due to lormalinl; l.vnlier A Caltewater iH.ivne & Worrall 1980: weights arc ol Mussels t> cm long: these were tranrfecmed to those of 3 cm using regressions given in iheir paper). content per prey starts to decline earlier in the winter. It is not likely that the accessible fraction in winter differs much when areas at different latitudes or average sea water temperatures are compared. ED However, it does not follow thai, for all wader species, ihe feeding conditions are always worse when the ambient temperatures are low. First, the llesh content of prey may be better: Macoma and Scrobicularia lose more body weight in mild winters than in cold ones (Zwarts 1991. Beukema 1992b). Moreover, there are incidental occasions in winter, usually associated with a large drop in temperature, when the benthic food becomes highly available to birds. Arenicola and Nereis may leave their burrows to migrate to deeper water (Werner 1956, Verwey 1958. Dankers & Binsbergen 1984) and many worms become stranded and can be easily picked up from the mud surface (Zwarts unpubl.). Furthermore, during and after periods of frost, moribund Cerastoderma with gaping valves provide a rich food resource lor gulls and waders that have remained (Zwarts unpubl. 1. Finally, during the winter half of the year. Nereis use a feeding method that makes them easy prey for birds. Whereas in summer they mostly remain in their burrows to filter food from the overlying water, in winter they feed more frequently on the substrate around their burrows, especially on sunny days in late winter and early spring (Esselink & Zwarts 1989). This is why Curlews feeding on Nereis achieve their highest intake rates in late winter, and not in summer or aulumn (Zwarts & Esselink 1989). The surface feeding by Nereis also gives Redshank the opportunity to sw itch to Nereis at low mud temperatures when the surface activity of the preferred prey Corophium is already inhibited (Ooss- Custard 1969). Further research should focus on the profitability and availability of benthic prey for wintering waders along the East-Atlantic coast. This means thai il is necessary to collect data on the body condition, burying depth, surface activity and defecation rates of the prey. Il will not be easy to show latitudinal variation, however, since, as shown and discussed above, at any one place large annual differences may be expected in the profitability of the prey and in the fraction available to waders.
Chapter 3 BURYING DEPTH OF THE BENTHIC BIVALVE SCROBICUIARIA PLANA (DA COSTA) IN RELATION TO SIPHON CROPPING Leo Zwarts pubtiiihed in: J. exp mar. Biol. Ecol. 101: 255-289 (1986) 83
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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
Page 35 and 36: SEASONAL VARIATION IN BODY WEIGHT O
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 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
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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: where they switch to surface-living
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
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
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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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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
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BreyT. 1989. Der Einfluss physikali
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latie tol chironoiiiiilen en de wai
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huch der Vogel Milteleuropas, Band
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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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