Ecoscript 34

34 Curry-Lindahl. Ecological requirements of herons, ...

As an order herons and their allies show a rather wide range
of habitats for nesting, roosting and feeding purposes. This
is true also for colonially nesting species. This ecological
range within an order that is distributed on all continents
except Antarctica is not surprising. The order is also repres-
ented in Oceania.

Many herons, ibises and storks are migratory. Some are long-
distance migrants between different continents. Although seve-
ral species are rather flexible as to habitats, the majority
is specialized to certain types of environment and food. Many
herons are successful and expanding in range, while several
ibises and storks are confronting environmental difficulties,
causing a decrease in number and a shrinking in distribution
range, All these factors are important and should be borne in
mind when discussing the conservation and management problems
of an order as cosmopolitan as the Ciconiiformes.

We are in this paper confronted with 61 or 63 (depending on
the systematics of herons) species of herons, ibises and
storks which have the habit of colonially nesting. The total
number of species of these three groups is 111, some more than
half of them is colonially nesting. This is a large propor-
tion, because 87% of the species of birds are solitary nes-
ters. However, colonial nesting is disproportionally common in
bird species that eat freshwater or marine food and in those
that eat seeds or fruit.


Preface 1
Introducing remarks 4
1. Why nest in colonies? 10
1.1 Food requirements 12
1.2 Critical habitats 13
1.3 Marine habitats 14
1.4 Estuaries and brackish waters 14
1.5 Mangroves 15
1.6 Coral reefes and coastal lagoons 18
1.7 Rocky coasts 18
1.8 Freshwater habitats 18
1.9 Terrestrial habitats 21
2. Conservation and management of wading birds and
their habitats in relation to development 23
2.1 Status of endangered species and reasons for decline 26
2.2 Regression of non-endangered species in northern
Africa 29
2.3 Regression of non-endangered species in Europe 30
2.4 Conclusions on reasons for decline 35
2.5 National parks and nature reserves 36
2.6 A conclusive proposal 37
Summary 37
Literature 39