Hydro-ecological relations in the Delta Waters
Hydro-ecological relations in the Delta Waters Hydro-ecological relations in the Delta Waters
Overall population size Fs very irpporCane as well. Indeed in the last decades a few species, lac the Greylag Gowe (Pig. 8) and the Coxmurant, Wreased in numbers in the Delta area. phis is not due fa any ehanges in the fbbd suepl~ hut to an overall increase in the population. In Europe the Greylag population ha* increased from 30 DUO to 1% 000 bemen 1974 and 1984 (Madaen, 1987). The total population size of arctic breeding wecies eau vary substantially between years due to the varying breeding success. Of ether spactes (e.g. DuW) pspulatiwn siae decreased dwriqg the last years, a declfae which is obvious in the couunte from the Delca area. Tlvese were all Eacrors ac~tiqg on a lazge sea&. M the DeLlt area itself, several z~pccts rYf prey reLettfon may fafluence the diatribwtion af a species. In she asalf,t~s prasent-a ad1 prey 8pedea were lrrmped ed4?aca large categeiesi Same species are, hCmemr, uee specXaLiz&. IeeakrD, vh@reas Others feed a* a large vazlaty of p?* species. Tlris may affect the occurreace ti£ birds qutte subgtantliaf.ly. In the Veerse Neex Dlva sp. fo- a v.&y important prep item far hehivor~e Such ns eonss aud Br*nt Geese.. nse to predarlqu and *be natural mortality of the plant* the aviril&le amount ,of Qlve q. declines rapidly *u.tumn vwdnter. bnring that the BanL Geese switch eo *Chef pray available in ehe area. d d y pastures .W$ asaMe land, a& their nmbers replain stable wnrii April-Hay (Fig. 91. Owte, kqwevez, do net change diet and amhers start te decline aireaey in Jmwarp, mch earlier tkaa in other part6 of the De~lta. Even for birtl4 Se4ddfs$ aa me prey fssp.eei&s, t&ce mi@t be facmts compli~wzing the relative prey abondande m hird dasiff. The i2ystet"aatehn is the most nwraus %del ,gp.eel&s in €he Wd*refm&el~& and ie a.lmst edcrusivelg faeds m 'Cockle* and Mussels,, %irB back Inbtvlda2 cinly feeczing on One of tW&L? %~&Les. %-he selertiw of mnssels ha8 W& s~turliQd in detail lHerr& w d ErySnck. 1986.3 Mere, 1B871 sad it is ~mtnd thde there is n6t mily selectiim foi laper miwels but even Eo? the chin%er-shelled i@ivfd+ls wishin a lengch cLies,. It has h~en shoran that these selection patterns are etuced by energeti'f constraints. Wile the pp6t .~pening-.&l eureseL6 %a wt rewartB.ng due to very -U ylela of fl,osh, tha thick sirelied mussele
OCLURRENCE AND DIET QF B ~T .tUQ 80 - a 2 40'- U (D 8 -20 SBP w'r N~SY 6x0 J& F.XS APE ,,g. I,. 1 m 0 066URANCti AND LEET DF IFT 108. -- - l00 W U L W - 60 G, 9, DI 2 D 2QL 0 b Q SBP QdT NOW S2SW JW FFsB AQE >, -ZQ @ are too hard to open. Tbis selection pattern implies that only a part of the prey population is really available to the birds, caused by the selectitin-behaviour of the birds themselves. Eowever, prey availabilicg is often influenced by the prey itself. In intertidal areas many maerobenthic spec%es may be buried deep in the substrate, well beyond
- Page 88 and 89: mudflats have retreated some 100-20
- Page 90 and 91: aq811~33a.e~ pue 3pTatlJS uxaJsafi
- Page 92 and 93: Erosion by waves of sandy shoals (c
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- Page 98 and 99: ECOLOGICAL DEVELOWdENT OF SALT MAKS
- Page 100 and 101: fn tidal water systems sedimentatio
- Page 102 and 103: hierarchical position. Tn the egtua
- Page 104 and 105: Of course. tke environmental change
- Page 106 and 107: wind erasson, desaliuation, aeratio
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- Page 110 and 111: Grevelingen. Lake Veere and Krammer
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- Page 116: BEEEXNX, W.D. and 80ZBf&. J. L9M. T
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- Page 121 and 122: this volume or in Duutsaa, et aL, 1
- Page 123 and 124: artificial waterflow was created af
- Page 125 and 126: of waterbirds occur regulsrly. The
- Page 127 and 128: . DISTRIBUXIOBI OF WATEJBIRoS OVER
- Page 129 and 130: small bird$ extludiag them vill net
- Page 131 and 132: In order to lsok for relatiouehips
- Page 133 and 134: Table 3 Biomass of macroroobenthos
- Page 135 and 136: freshwater basins. Clearly the pres
- Page 137: scmthem bottueary o-f the winter di
- Page 141 and 142: 5.2 H- factors Next to all fartors
- Page 143 and 144: Bewick's Swans (Cygnus columbariusl
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- Page 149 and 150: DOQiWT$QS, G. 4 TWISK, F., 1987. De
- Page 151 and 152: MEININGEB, P.L. and HAPEREX, A.M.M.
- Page 153 and 154: PISCIVORES Litfle Grebe Great Crest
- Page 156 and 157: IPYBRO-EGOLOOIOAL BELATIONB ZN THE
- Page 158 and 159: apart from upstream purification; -
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- Page 164 and 165: Nature is pliable. Belattvely young
- Page 166 and 167: Ro. 1. No. 2. SQ. 3. Investigations
- Page 168 and 169: 25. The relation between water quan
Overall population size Fs very irpporCane as well. Indeed <strong>in</strong> <strong>the</strong> last<br />
decades a few species, lac <strong>the</strong> Greylag Gowe (Pig. 8) and <strong>the</strong><br />
Coxmurant, Wreased <strong>in</strong> numbers <strong>in</strong> <strong>the</strong> <strong>Delta</strong> area. phis is not due fa<br />
any ehanges <strong>in</strong> <strong>the</strong> fbbd suepl~ hut to an overall <strong>in</strong>crease <strong>in</strong> <strong>the</strong><br />
population. In Europe <strong>the</strong> Greylag population ha* <strong>in</strong>creased from 30 DUO<br />
to 1%<br />
000 bemen 1974 and 1984 (Madaen, 1987). The total population<br />
size of arctic breed<strong>in</strong>g wecies eau vary substantially between years<br />
due to <strong>the</strong> vary<strong>in</strong>g breed<strong>in</strong>g success. Of<br />
e<strong>the</strong>r spactes (e.g. DuW)<br />
pspulatiwn siae decreased dwriqg <strong>the</strong> last years, a declfae which is<br />
obvious <strong>in</strong> <strong>the</strong> couunte from <strong>the</strong> Delca area.<br />
Tlvese were all Eacrors ac~tiqg on a lazge sea&. M <strong>the</strong> DeLlt area<br />
itself, several z~pccts rYf prey reLettfon may fafluence <strong>the</strong><br />
diatribwtion af a species. In she asalf,t~s prasent-a ad1 prey 8pedea<br />
were lrrmped ed4?aca large categeiesi Same species are, hCmemr, uee<br />
specXaLiz&. IeeakrD, vh@reas O<strong>the</strong>rs feed a* a large vazlaty of p?*<br />
species. Tlris may affect <strong>the</strong> occurreace ti£<br />
birds qutte subgtantliaf.ly.<br />
In <strong>the</strong> Veerse Neex Dlva sp. fo- a v.&y important prep item far<br />
hehivor~e Such ns eonss aud Br*nt Geese.. nse to predarlqu and *be<br />
natural mortality of <strong>the</strong> plant* <strong>the</strong> aviril&le amount ,of Qlve q.<br />
decl<strong>in</strong>es rapidly *u.tumn vwdnter. bnr<strong>in</strong>g that <strong>the</strong> BanL Geese<br />
switch eo *Chef pray available <strong>in</strong> ehe area. d d y pastures .W$ asaMe<br />
land, a& <strong>the</strong>ir nmbers repla<strong>in</strong> stable wnrii April-Hay (Fig. 91. Owte,<br />
kqwevez, do net change diet and amhers start te decl<strong>in</strong>e aireaey <strong>in</strong><br />
Jmwarp, mch earlier tkaa <strong>in</strong> o<strong>the</strong>r part6 of <strong>the</strong> De~lta.<br />
Even for birtl4 Se4ddfs$ aa me prey fssp.eei&s, t&ce mi@t be facmts<br />
compli~wz<strong>in</strong>g <strong>the</strong> relative prey abondande m hird dasiff. The<br />
i2ystet"aatehn is <strong>the</strong> most nwraus %del ,gp.eel&s <strong>in</strong> €he Wd*refm&el~&<br />
and ie a.lmst edcrusivelg faeds m 'Cockle* and Mussels,, %irB back<br />
Inbtvlda2 c<strong>in</strong>ly feecz<strong>in</strong>g on One of tW&L? %~&Les. %-he selertiw of<br />
mnssels ha8 W& s~turliQd <strong>in</strong> detail lHerr& w d ErySnck. 1986.3 Mere,<br />
1B871 sad it is ~mtnd thde <strong>the</strong>re is n6t mily selectiim foi laper<br />
miwels but even Eo? <strong>the</strong> ch<strong>in</strong>%er-shelled i@ivfd+ls wish<strong>in</strong> a lengch<br />
cLies,. It has h~en shoran that <strong>the</strong>se selection patterns are etuced by<br />
energeti'f constra<strong>in</strong>ts. Wile <strong>the</strong> pp6t .~pen<strong>in</strong>g-.&l<br />
eureseL6 %a wt<br />
rewartB.ng due to very -U ylela of fl,osh, tha thick sirelied mussele
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