Hydro-ecological relations in the Delta Waters

$oseibilities to create ptentially vaiuable breeding sites for
characteristic coastal breeding birds. By meem of changing the
hydralogy, e.g. by (partially) inumlating 8maU polders adjacent to the
OostersmheLde ancl the Westerschelde, the importance far birds can be
improved. In most places the ever increasing pressure bp recreational
activities (boating, wind-surfers, walking, bait-digging, fishing etc.)
is a serious threat to the various functions for birds. In particular
the intertidal areas are highly vulnerable to disturbance, and measures
to reduca this disturbance are required. The same applies to some of
the shallow parts of the Veerse Meer and Grevelingen Meer, which are
increasingly visited by wind-surfers, not only in snmmer but also in
winter! Simple measures (snch as float* cablw) can be takeu to make
at least dtome of these areas inaceessibSe.
6 CONCLUSION
The Creation of new habitats by damning up eetuaries has, beyond doubt,
increased the diversity of bird life in the Delta. QT both breeding and
non-breeding birds several species increased in riders, Lass is known.
havexer, on the changes in population size of the species OriginaIly
present, although there are indications their populations did not
deurease markedly until 1984. Birds quiekly reacted to the MW
habitats
created, and the Voordelta, the estuaries, the aline and the fresh
lakes each have now their more or less tyaical avifauna. The gradient
in abiotio and biotic ~onditions is very well lreflerted by the
distribution of the different bird groups a+ well as by the individual
species, liowever, notwithscanding the attention paid to nature
consemation in the e l y czeared habitats. the estvarise areas still
accomdate the largest numbers af birds. It ehould also be stressed
that all estuarine ec@wetems, and especially brackish and freshwarer
tidal habitats are on a global scale very rare habitats, *hi& should
MW be completely protected. Thelr loss can not be compensated bp the
creation of new habitats.
For several bird species or groups it is s hm that their distribution
and abundance is closely linked to that Oe their food sapply. An,y