In The Netherlands, arising in geological time as the delta of the rivers Rhine, Meuse and Scheldt, a considerable change in landscape occurred during the Holocene period due to sea level rise. In more recent times this change was dramatically enforced by human actions. This started with the opening up of the large woods on higher soils, some 4500 years BP. It is estimated that the country was only populated then by a few thousand people. During the next 2000 years, the extensive forest clearing continued, and up to approximately 60% of the upland area changed into grazed woodland. Over-exploitation during the Middle Ages resulted in extended heathlands, which covered up to 40% of the total area of upland sands by 1500 AD. Today woodlands cover only 1 promille of the surface area it covered 7000 years ago. Wetlands remained undisturbed for a long period, but they have become seriously affected since the late Middle Ages; the construction of dikes, embankments and drainage have caused the area of wetlands to shrink dramatically. Especially when in the 19th and 20th centuries, as a result of the introduction of steam and later diesel and electric engines, large-scale projects could be realised. This led to the disappearance of many freshwater lakes and the almost complete loss of the area of brackish water, the natural link between sea water and freshwater. Although the influence of Man upon the Dutch landscape commenced some 4500 years ago, it is only during the last 600 years that wetlands have been affected. Particularly the last 100 years have been crucial with respect to drainage and cultivation. By reconstructing ancient landscapes, an attempt has been made to describe the species composition and numerical abundance of waterbirds, starting 7000 years BP. Two species have become extinct in the territory, many others show changes in abundance. The start of agriculture has caused a major change in the food provisioning of many herbivorous waterbirds. Over the last 7000 years, a sevenfold increase of the number of herbivorous waterfowl is estimated. On the other hand the number of fish-eaters, benthos-eaters and planktivorous waterbirds has declined, their available habitat now having diminished by 45%, 36% and 55% respectively with respect to the Late Subatlantic period, c. 850–1350 AD.

In this paper long-term developments in the breeding populations of 23 typical marshland bird species in The Netherlands are reconstructed, using data of several monitoring schemes and atlas studies, as well as published sources. Twelve species increased in numbers since the 1950s: Great Cormorant Phalacrocorax carbo, Great Egret Casmerodius alba, Little Egret Egretta garzetta, Eurasian Spoonbill Platalea leucorodia, Greylag Goose Anser anser, Red-crested Pochard Netta rufina, Western Marsh Harrier Circus aeruginosus, Bluethroat Luscinia svecica, Common Grasshopper Warbler Locustella naevia, European Reed Warbler Acrocephalus scirpaceus, Penduline Tit Remiz pendulinus and Common Reed Bunting Emberiza schoeniclus. Nine species declined: Great Bittern Botaurus stellaris, Little Bittern Ixobrychus minutus, Black-crowned Night Heron Nycticorax nycticorax, Purple Heron Ardea purpurea, Black Tern Chlidonias niger, Savi's Warbler Locustella luscinioides, Sedge Warbler Acrocephalus schoenobaenus, Great Reed Warbler Acrocephalus arundinaceus and Bearded Reedling Panurus biarmicus. For Water Rail Rallus aquaticus and Spotted Crake Porzana porzana numbers fluctuated without a clear trend. Species typical of uncut reedbeds over standing water declined most strongly, whereas the majority of species preferring drier marshlands with shrubs and bushes, and species with a rather broad habitat choice, on average Increased. Possible causes of long-term population developments are discussed. At present, changes in water table management, falling water tables, terrestrialization and eutrophication have the highest impact on trends of marshland birds in The Netherlands.

With the loss of natural wetlands in western Europe, conservationists involved in ‘restoration projects’ become increasingly interested in eastern Europe for reference. In Poland, for example, still some 5% of the country is covered by fen mires, raised peat bogs and other types of wetlands. Although not in a pristine state anymore, size and quality of these wetlands are still sufficient to guarantee high biodiversity and a buffer against stochastic events. If anything, these reserves show that size really matters, and also that any attempt at ‘restoration’ of a pristine state is doomed to failure.

Wetlands in the Mediterranean area have become a rare habitat due to human impact. To model the ecology and breeding biology of birds depending on that habitat, we describe long-term studies on two wetland birds (Little Egret Egretta garzetta and Greater Flamingo Phoenicopterus (ruber) roseus) in the Camargue, France. The hydrological conditions in natural Mediterranean wetlands depend largely on the pattern of rainfall (winter) and evapotranspiration (summer), but have been substantially altered by human activities. In natural conditions, these wetlands are very diverse and therefore sustain a high diversity of breeding birds. At the same time their unpredictable nature favours opportunistic breeding and wintering strategies of their inhabitants. Colonial waterbirds depend on wetlands both for safe nesting sites and for foraging. Availability of suitable nesting sites may limit breeding numbers. Availability and diversity of wetland habitats as foraging sites affect the number and density of breeding species that an area can sustain. Unfavourable feeding conditions can reduce the number of birds that attempt to breed and the number and quality of offspring the birds produce. Apart from local environmental factors, dispersal between wetlands in the western Mediterranean and existence of a non-breeding pool also affect breeding numbers in the Camargue. Thus, the persistence of wetland birds in the Mediterranean depends both on a network of habitat types on a local scale and a network of wetlands on a regional scale.

The man-made wetlands in young polders in The Netherlands are important stopover and wintering sites for geese. We studied trends in vegetation composition and goose density in two study areas. One was located in a nature reserve situated in a polder reclaimed from an estuary, the other in a reserve in a polder reclaimed from a freshwater lake. In the former we compared an area of spontaneous vegetation succession with a summer-grazed area. In the latter the effect of reed Phragmites australis cover and height on field selection of geese was studied in an area grazed year-round by cattle and horses. In both study areas the area of short grassland (reed cover about 1%, reed height <0.5 m) was found to be significantly positively related to the grazing density of cattle and horses. Migrating and wintering Greylag Geese Anser anser and Barnacle Geese Branta leucopsis preferred to feed on these extensive short grasslands. In the ungrazed part of the study site in the reclaimed estuarine area, there was an inverse relation between goose density and the ousting of pioneer species of saline habitats and short grasses by tall species such as Calamagrostis epigejos, Phragmites australis, tall herbs and shrubs. Summer grazing by cattle and horses at stocking rates of about 0.4 to 0.9 animals/ha, retarded the vegetation succession to some extent, which resulted in a goose density being higher in the summer-grazed area than in the ungrazed area. The implications for management are that the more desalinated the area becomes and the higher its clay content, the higher the stocking rate must be to retard the vegetation succession.

The relationship between reed Phragmites australis cover of ditches and habitat use by marshland birds was studied in an experimental area of the Oostvaardersplassen nature reserve in The Netherlands. Water table and grazing by cattle and horses had an important impact on the development of P. australis in ditches and pools, resulting in three different types of habitat: deep open water, shallow open water and shallow water with P. australis vegetation. Shallow water bodies with a reed cover of less than 10% were most frequently visited by foraging Eurasian Spoonbill Platalea leucorodia, Smew Mergellus albellus, herons, ducks, waders and rails. Breeding grebes and marshland passerines, however, preferred parts with more reed cover. It is concluded that the creation of shallow water bodies, together with adjusted water table management and grazing pressure are suitable tools for restoring habitats preferred by marshland birds.

A study on Bearded Reedling Panurus biarmicus feeding habits in combination with a sample-wise breeding bird survey of the marshland zones of the Dutch wetland Oostvaardersplassen shows clear-cut spatial differences in densities and habitat use. The more mature stands of Reed Phragmites australis constitute the main nesting area, while the more open, younger stands, particularly when inundated and grazed by moulting Greylag Geese, provide the main feeding areas. Arthropod, and especially Chironomid, densities were generally higher in grazed Reed stands and frequent feeding flights were carried out by parent birds between grazed and ungrazed parts of the area during chick raising. Chironomids also proved to constitute the main prey items brought to the nests. Apart from higher prey densities in grazed stands, better detectability as well as better accessibility of the lower vegetation layers are also likely to contribute to the habitat preference of insect-feeding Bearded Reedlings. When in winter the birds shift to Reed seeds, patches with higher seed index hold higher densities of feeding birds. When seed index drops below a certain level, density of birds is low and independent of seed index. The highest seed production is associated with rejuvenated Reed stands, recovering from previous grazing. Bearded Reedlings thus highly depend on the early successional stages of Reed stands. Temporal and spatial habitat diversification is mediated by changing water levels and rejuvenation caused by grazing geese. A number of other marshland bird species depend on this type of vegetation, and wetland management should therefore aim at favouring the natural processes governing Reed succession.

After having almost completely vanished from The Netherlands by the 19th century, from the 1970s onwards the Great Egret is increasing in numbers again, particularly in the newly created wetland of Oostvaardersplassen. During the first 25 years, the rate of re-colonisation has been extremely low, the resident population never exceeding five breeding pairs. From 2000 onwards, however, following the extension of the surface area of shallow marshland, the number of breeding birds increased to 45 pairs. This paper deals with the feeding ecology of the Great Egret during 1976–99, when numbers were at a low level. Individual differences in food choice and feeding habits were studied in order to gain insight into the key factors for establishing and maintaining a healthy population. Observations on foraging birds were carried out during 1987–92. The birds foraged mostly within the reserve. From March to July they preferred foraging in ditches, changing to Reed borders of shallow pools and dry grasslands from August onwards. In the ditches, Three-spined Stickleback Gasterosteus aculeatus, other small fishes and tadpoles were the main prey (91.4% of all prey items). In the shallow water bodies the egrets caught almost exclusively sticklebacks, and in grasslands Common Voles Microtus arvalis. One bird was observed feeding near fishing boats, taking Perch Perca fluviatilis and Roach Rutilus rutilus of 10–20 cm length. When feeding on sticklebacks, a Great Egret had to forage for 1.5 to 3 hours to fulfil its daily needs. When scavenging on larger fish around fishing boats only 15 minutes sufficed, but the energy expenditure was likely to be higher due to commuting flights and inter-specific competition with Grey Herons Ardea cinerea. However, for the majority of Great Egrets the shallow and transparent water in ditches and pools with a high abundance of young sticklebacks and some coverage with emergent vegetations proved to be the most profitable feeding habitat. The decisive factor underlying the spectacular increase in recent years has probably been the creation of clear and shallow freshwater pools and inundated grasslands in the formerly dry border zone of Oostvaardersplassen. These foraging grounds lie close to undisturbed breeding sites. This finding may prove useful for wetland restoration elsewhere in The Netherlands.

Black Terns Chlidonias niger have shown a decrease of well over 90% as a breeding bird in The Netherlands during the twentieth century. Two hypotheses have been put forward for this decline: the disappearance of the floating plant Water Soldier Stratiotes aloides, which used to be the favourite nesting substrate of the terns, and a decrease of available insect food for the chicks, notably dragonflies. Both effects are attributed to eutrophication of surface waters. Reproductive bottlenecks vary greatly among areas and habitats. In river landscapes, no signs of food shortage could be found, and loss of nesting substrate has been successfully compensated for by offering artificial nest rafts. Extremely low fledging success in moors and in lowland grasslands is caused by food problems. In this case, artificial rafts are less successful. With decreased insect availability, fish and earthworms have become more important in the chicks' diet, but these are less reliable as a food source. Fledging success greatly depends on the amount of fish in the diet. Also, a minimum amount of fish is always needed to cover the calcium need of the chicks. In north-eastern Poland, there were no problems with either nesting places or food for the chicks.

The coastal wetlands of The Netherlands have always served as winter haunts for juvenile and immature White-tailed Eagles from breeding populations further north and east. Even as these populations were at their lowest ebb by the 1960s and 1970s, each winter a few individuals showed up, invariably favouring large wetlands with a good supply of wintering, mainly herbivorous, waterfowl. An analysis of the presence of eagles in the wetland Oostvaardersplassen showed that wintering numbers as well as the duration of individual stays increased as a function of the number and biomass of waterbirds present. During the pioneering stage of this newly reclaimed area the dynamic vegetation produced huge seed supplies that attracted vast numbers of herbivorous waterbirds. The increase in eagle numbers in the Oostvaardersplassen reserve preceded the recovery of the northern and eastern breeding populations of Whitetailed Eagles, but did not increase any further after reaching a maximum of 3–4 wintering birds, despite the fact that wintering numbers elsewhere in The Netherlands continued to rise in the wake of the increasing breeding population elsewhere in Europe. It is argued that ‘core area’ Oostvaardersplassen became saturated each winter in the 2000s. Additional eagles reaching The Netherlands spent the winter at alternative sites with smaller food supplies. In 1997–99, new waterbodies were created in the dry border zone of Oostvaardersplassen. The subsequent boost in waterbirds and fish may have triggered — in combination with the presence of undisturbed breeding habitat — the summering, and eventual breeding, of White-tailed Eagles from 2004 onwards. Water management towards improving dynamics in larger wetlands (both estuarine and riverine) may further boost food supplies for waterfowl and, hence, create suitable habitat for White-tailed Eagles elsewhere in The Netherlands.

We studied dispersal of Great Reed Warblers Acrocephalus arundinaceus, using a mark—resight model for dispersal. We assessed the relevance of ecological distance, defined as movement along reed edges, as opposed to straight line distance for predicting the distribution of dispersal. In a mark—resight study in the northern Netherlands, 1158 birds were ringed. 178 birds were resighted at least once, with 254 movements between known nesting locations in successive years. Dispersal was defined as movement between successive nesting sites, and modelled as an exponential function of ecological and geographical distances. To correctly model dispersal probabilities in the fragmented study area, the model discriminates between suitable habitat sections and intermediate gaps. Several nested models for dispersal were compared by means of the likelihood ratio test. Models incorporating ecological distance gave a better fit than models using geographical distance, although the difference was not large. To describe dispersal probabilities, combined models were necessary at both local and long distance scales, and separate models were needed for juveniles and adults. For a landscape without gaps, the parameter estimates of the best model can be interpreted as follows. An estimated 65% of the adult dispersal distances were within a close range of the previous nesting location with a mean ecological dispersal distance of 0.58 km. The remaining 35% had an estimated mean distance of 10.3 km. An estimated 39% of the juvenile movements were random over the study area. The remaining 61% had a mean dispersal distance of 3.1 km. These results suggest that there might be two dispersal strategies in the Great Reed Warbler. There is also an indication that adults disperse further when connectivity decreases. These findings indicate that dispersal of Great Reed Warblers is not random, but smaller dispersal distances are more likely than larger distances. This might result in a limited dispersal ability of the species over the fragmented landscape.

Large and heavy birds usually use soaring flight during long-distance migration or make regular stopovers en route for substantial refuelling. Purple Herons are large, long-distance migrants. Because of their size, large herons migrating southwards from Europe to Africa were expected to make one or more stop-overs to refuel. However, data from seven Purple Herons, fitted with satellite transmitters, showed that the herons were able to cover the distance into the Sahel of about 4000 km within 5–7 days. One individual even flew 5600 km non-stop, mostly over sea. The herons migrated mostly at night and partly during the day with a high travel speed indicative of flapping flight. The herons made few diurnal stops in Europe and North Africa. Substantial ‘stopover’ time was limited entirely to a period of several weeks before departure, and after arrival south of the Sahara. We assume that this is energetically possible for birds with a maximum wing load of 4–5 kg body mass per m2 of wing surface. Larger wing loads as in storks or raptors prescribe soaring or refuelling with the consequence that most migratory journeys to African wintering grounds then take at least a month. The results emphasize the conservation importance of abundant and high-quality feeding habitat near the breeding areas for pre-migratory fuelling of this species. Furthermore, arrival habitat is likely to be more essential than previously expected. We suspect that the lack of suitable arrival habitat might explain the observed high adult mortality in dry Sahel periods better than ‘winter’ survival.

All over Europe, wetlands have decreased in size, lost their original dynamics and became fragmented as the consequence of an ever increasing human land use. These processes have resulted in losses of nature values, among which declines in marshland bird populations. Ecological restoration of wetland systems follows from initiatives like EU Bird and Habitat Directives and Water Framework Directive, but may be, in itself, too costly to be widely applied. More promising perspectives to reinforce the wetland part of the ecological network Natura 2000 might come into focus when combined with spatial water management which is primarily aimed at more sustainable safety against flooding. In this way, the wetland network may acquire a wider public and political support. Knowledge on scale-related habitat use of wetland birds can play a role in the process of spatial planning. We illustrate this point by distinguishing four levels of spatial and temporal habitat use by wetland birds, and giving examples for each. The four levels are: (1) birds on stopover sites during migration, (2) territorial breeding birds, (3) colonial breeding birds, and (4) staging birds on wintering sites. This asks for ecological coherence on different scales, e.g. on the international level of migration flyways, on the regional level of landscapes and on the local level of individual wetlands. It is advocated that wetland ecologists dedicate themselves more specifically to quantifying the relevant data on habitat use of birds on each of these scale levels. Meanwhile, spatial planners should try to incorporate them into their efforts in realising combinations of ecological restoration or rehabilitation of wetlands and solutions for sustainable water management. These combinations might turn the tide for some seriously threatened species of marshland and wetland birds.