Albert Beintema, Oene Moedt, and Danny Ellinger, 1995.
Schuyt & Co, Haarlem. 352 p, quarto. Numerous colour photographs. ISBN 90
6092 391 7.
Figures and tables are not included
A screaming black-tailed godwit on a fence post. Lapwings, performing their acrobatic flights against a beautiful sky, above lush meadows dotted with flowers. A drumming snipe in the early morning, and a flock of male ruffs, indulged in their silent mock fights. These are the traditional symbols of Dutch polder land. Meadow birds, the most characteristic group of birds of the Dutch landscape.
This picture of Dutch polders is changing. Farmers on wooden clogs are no longer a common sight. Instead, heavy machinery dominates the landscape. Most of the flowers have gone. Grasslands have changed into monotonous sheets of brilliant monochrome green, like a billiard.
Yet, the acrobatic lapwings are still to be found, and godwits still scream. How are our meadow birds doing today? Where are they to be found? Why do we have so many of them in the Netherlands as compared to neighbouring countries? What makes a meadow bird a meadow bird? And what can we do to keep them for the future?
Originally, before man started to cultivate his environment, there were no meadows, and consequently there were no meadow birds. Surely, the species were there, but they all lived somewhere else. Either in other habitats in the Netherlands, or in other countries, where natural grasslands occurred. They became meadow birds after man created agricultural grassland. The basic things we offered them were food and safety. Food in the form of soil and surface fauna, safety in terms of available time to raise a family, without interference. In both respects soil conditions, and our unpopular wet climate have played an important role. The best meadow bird soil consist of wet peat, covered with a layer of clay, deposited during transgression periods of the neighbouring sea. The secret is humidity. This is where the wet climate also helps. Due to the humidity, the grass grows slowly, and cattle grazing or mowing can only take place relatively late in the season.
Food conditions have been improved by manuring. But fertilization also speeds up the grass production, and advances grazing and mowing dates, thus reducing the chances to safely raise a family. The intensification process in dairy farming has two counteracting effects: increased food abundance, allowing higher densities of birds, and reduced possibilities for safe reproduction. The peat-clay combination proves best, because on the one hand the fertile mineral layer, in combination with manure, yields the highest densities of food organisms, while on the other hand the wet peat underneath assures postponement of grazing and mowing. The wet climate helps to keep the upper surface moist, so bird bills can probe for soil fauna throughout the nesting season.
As a result of the two counteracting forces in grassland management, there is a lower limit of minimum intensification required, above which the meadow bird phenomenon can develop, and an upper limit of maximum intensification tolerated, above which the whole system collapses. Both limits vary between species, depending on food requirements, timing of nesting, and specific mortality rates. Hypothetical ranges of tolerance for a number of species are presented in figure 1.1. It has been argued that 'meadowbirdification' becomes profitable in smaller species at lower fertilization levels than in large species. Also, smaller, and especially late nesting species, are more vulnerable towards advanced mowing dates and increased trampling by cattle.
Because no meadow bird has been a meadow bird by origin, there is no sharp definition of meadow birds versus non-meadow birds. In The Netherlands it has become customary to distinguish 14 species of 'primary' meadow birds, not primary in terms of origin, but of primary habitat use. Primary meadow birds depend on agricultural grassland for a 'larger part' of the Dutch population, and occur as such in a 'larger part' of the country. Another 14 species are called secondary meadow birds. These depend on grassland for a minor part of their population, or do so on a local scale only (table 1.1).
In contravention to the systematic rules this chapter opens with the waders, the most conspicuous and noisy members of meadow bird society.
The data on the primary meadow birds are more detailed than those on the secondary ones. Descriptions comprise the Dutch, English and scientific names, notes on adult and juvenile plumages, locomotion, voice, habitats, food and foodcollecting, breeding (nestsite, eggs, incubation), parental care, migration and age.
A table presenting the most recent data on the breeding populations of all European countries (appendix, p. 324) and two maps, indicating density and distribution in the Netherlands and in Europe, have been added.
As the existence of agricultural grasslands is restricted to a few thousand years, the question of the ecological and even the geographical origin of our meadow birds arises. Meadow birds have lived - and in small numbers still do so - in open areas with low, scarce and even lacking vegetation in the middle- and high-latitude parts of Europe and Asia. Various factors inhibiting or preventing treegrowth lead to the development of steppe- and prairiegrasslands, alpine meadows, tundra, saltmarshes and blanket bogs. On a small scale natural grasslands developed in sanddunes and riverbasins.
The beginning of the Holocene era (ca. 8000 BC) was marked by rising temperatures which caused the sea level to rise. Ca. 4000 BC the Dutch coastline roughly coincided with the present one. Large areas were transformed into broad tidal flats and saltmarshes, bordered in the west by sandridges, in the east by a belt of peat. Approximately 3000 BC new sandbars closed most inlets of the sea. In the now freshwater marshes peat started to grow and continued to do so, until around 1250 BC nearly all the lower parts of the Netherlands were covered with peat and blanket bogs. In the higher parts of the country stagnation of the natural draining had also caused widespread growth of blanket bogs. In the coastal parts of the Netherlands, settlement was largely influenced by the alteration of marine transgressions and regressions. People lived on natural ridges or refuge mounds (terpen). After ca. 1000 AD, building of dykes made permanent occupation of coastal regions possible. It eventually lead to the complete reclamation of the peaty regions of the western and northern Netherlands, and their transformation into agricultural grasslands. From the 16th century onwards, peat cutting in the eastern and southern parts of the Netherlands almost completely removed the blanket bogs. At the end of the 19th century, large areas consisted of wet meadows in the valley floors, with arable fields and extensive heaths - grazing grounds for manure supplying sheep - in the drier parts.
From 1787 onwards steampowered mechanisation of water control, improvement of draining, and the introduction of artificial fertilizers around 1870, started the transformation into a modern agricultural landscape. Nowadays 28% of the total Dutch area consists of intensively cultivated grasslands.
For the greater part of the avian inhabitants of these areas it is not clear at what moment in history they changed their natural habitats for the expanding artificial grasslands. For each species of meadow bird this process developed in a different way, at a different time and with a locally different character.
Archeological investigations offer only a small contribution to the knowledge of this process; all primary meadow birds did exist here from prehistoric times. Sixteenth century archives contain documents dealing with regulations on hunting, egg collecting, and trading, and therefore present a very one-sided view on postmedieval birdlife.
The first reliable Dutch book on birds is 'Jacht-bedrijff' (the business of hunting), probably published in 1635. All primary meadow birds seemed to be very common. Data on habitat preference fit wonderfully in contemporary knowledge. Between 1770 and 1829 'Nederlandse vogels' (Birds of the Netherlands), the first serious ornithological work in the Dutch language was published. Lapwings, ruffs, redshanks, snipes and black-tai- led godwits must have been very numerous in meadows, hayfields, fenlands and marshes. Oystercatchers and curlews inhabited coast and sanddunes.
For our knowledge of ninetheenth century birdlife we owe much to H. Schlegel and H. Albarda. In their description of the preferred habitats of meadow birds, presence of low lying wet meadows and marshes is stressed.
It is still difficult to get an overall view on the development of the meadow bird populations in the first half of the twentieth century. The first naton-wide cencus dates from the seventies. Of the preceding years only fragmentary data are known. These allow recognition of three trends: change in numbers, the size of the breeding areas, and distribution.
Numbers of critical birds (ruffs, snipes, redshanks) have decreased between 90 and 50%. The decline of curlews may have stopped in the sixties. Black-tailed godwits increased until the seventies. Oystercatchers showed a marked increase. Lapwings were, and still are, the most common meadow birds.
The breeding area of the ruff and more recently of the snipe is mainly restricted to the peat districts. Godwits expanded their breeding area. Oystercatchers and more recently curlews still do so.
In the recent past, each type of grassland used to have its own characteristic inhabitants. This situation has come to an end. Grasslands are uniform now and the non-critical meadow birds (lapwing, godwit, oystercatcher) are more evenly distributed. Sanddunes, marshes and heaths housed many meadow birds. Especially in the eastern parts of the country, the birds changed from these habitats to agricultural grasslands. Breeding in semi-natural sites is an exception now.
From prehistoric times meadow birds were shot, and their eggs and young taken. The first regulations date from the sixteenth century. Nowadays only limited shooting of snipes and ducks, and the limited taking of lapwing eggs is permitted. All other species and their eggs are actively protected now.
Chapter 4 deals with the social behaviour of primary meadow birds in the reproductive period. The description splits up in three chronologically ordered categories: territorial behaviour, pair formation, and parental care. The latter category includes breeding, and anti-predator responses.
The territorial behaviour of oystercatchers comprises the well- known piping ceremony, and two display flights: the butterfly- and the whirr-flight. In the pair formation, piping-, mating-, and scraping ceremonies are important. Incubating birds distract intruders by mock- breeding. Oystercatchers are very inventive in defending their young. Parental care comprises brooding and feeding. Predators are either attacked or distracted by various methods, including mock-breeding, crouch-running and several forms of injury-feigning.
In the territorial behaviour of lapwings the songflight is a main element. Fighting and threatening are common. In pair formation nesting- and rocking-displays are shown by males. Mutual scraping ceremonies precede mating. Incubating birds behave inconspicuously. Predators are chased by dive-attacking and mobbing. Towards animal and human intruders injury- feigning occurs. Empty egg shells are removed and hidden. Parents brood their chicks, exceptionally up to an age of three weeks. Families fall apart after fledging.
Black-tailed godwits show a high degree of nest-fidelity. They defend a relatively small breeding territory. In hostile encounters with conspecifics, various threat-displays are shown. Bill-gripping, fighting, and pursuit flights are common. In Pair formation, and probably in establishing a territory, (elements of) songflights are very important. In complete form this consists of rising, tumpling, tossing, diving, and landing with wings-high-display. Ceremonial flights are followed by sexual pursuit flights and (mutual) scraping ceremonies. Pre-copulatory behaviour is rather variable, but is always preceded by pursuit walk. Female chooses nest site. Female shows first egg to male. He approaches her with a ritualised gait, lifting his legs high above his back. Small chicks are brooded. Intruding birds are dive-attacked. Over ground predators godwits show hovering with dangling legs. Injury-feigning is very uncommon. The family stays together until fledging.
Since the seventies, curlews show a remarkable increase in agricultural grasslands in the sandy districts and riverbasins in the eastern and southern part of the country. Undulating songflight is important in pair formation and territory establishment. Various threat displays are shown. Fighting is not uncommon. Copulation is preceded by pursuit walk. Mutual scraping before nest site choice. Intruding birds are mobbed and chased. Injury-feigning to ground predators and humans is uncommon, cattle is sometimes attacked.
The territorial behaviour of redshanks is probably poorly developed. In pair formation songflight and sexual pursuit are very important. Mutual scraping displays and mock nest-relief precede copulation. Redshanks prefer nest sites in the vicinity of lapwing nests and take part in communal alarm against ground predators. They show no injury-feigning. The family stays together until fledging.
The snipe's cocked and fanned tail is instrumental in various displays: threatening, alarming, and precopulatory behaviour. Territorial claims are shown by drumming flight, which also has sexual significance. The wing-arch-flight is exclusively directed at the female. A pursuit walk precedes the copulation. The parents feed their young, which are sometimes divided between them. Anti-predator behaviour includes injury-feigning.
After a fast decline due to agricultural changes, ruffs are rare now. Communal courtship and mating occurs on arenas or leks. Two types of males: independent males defend a small territory on the arena, satellite males are not territorial, and are tolerated by the owners of a territory or residence. Territorial disputes with other males and courtship towards females are strongly interwoven. The behaviour of the females is crucial in the reproductive system. Females are clearly attracted by particular independent males or, on small arenas, by residences occupied by owner and satellite. A greeting ceremony precedes the arrival of females on the arena. Their behaviour determines what will happen. Wing-dropping and crouching almost invariably lead to copulations; preening indicates (tentative) unwillingness. The females copulate with several males. Nest- site choice, incubation and parental care is completely left to the females. Hogan-Warburg offers an interesting hypothesis on the evolution of two types of male reproductive strategies: 'On the residence immature naked-nape males perform a sexual type of behaviour, on the edge of the arena they behave agressively. It is not unlikely that genetic differences have existed among such immature naked-nape males in the evolutionary past, which influenced the relative levels of their tendencies to behave sexually or to behave agressively.'
The easily observable mallard's behaviour forms an example for the territorial and pair-formation displays of the three other species of meadow-inhabiting ducks.
All species engage in communal courtship with several similar elements: courtship flights, trio flights, mock-preening, turning back of head.
Pair formation of mallards usually starts in autumn. It comprises three different displays: water-flicking, head-up-tail-up, and down-up. Courtship ceremonies can lead to pursuit flights, as several drakes chase an unpaired female. A pair flying over a neighbouring territory illicits response of its owner, directed at the female of the intruding couple. So trio-flights consist of two males and one female. Fighting can be somewhat ritualised. After pair formation ritual drinking, mock-preening, and copulations are the most common displays.
Shovellers' courtship is less conspicuous. The drake defends a breeding territory. It leads to frequent chasing of, and fighting with, competing males. Males sometimes take part in parental care. A garganey also defends a breeding territory. The laying-head-back display towards the female is unique among related ducks.
Neck-stretch- and coughing displays are typical for tufted ducks.
The skylark, yellow wagtail and meadow pipit show a strong decline in agricultural graslands. The young of these nidicolous species leave their nests before fledging, which minimises the risk of predation. All three species perform song flights, very extended in skylarks, less conspicuous in yellow wagtails and meadow pipits. Song is also given from a perch. Pursuit flights followed by fights are common in male skylarks and yellow wagtails. Meadow pipits act more peacefully.
Courtship displays on the ground precede the copulation. Hopping and bowing are typical for skylarks. The nest site is chosen by both partners. Towards intruders skylarks and meadow pipits can show injury- feigning. Yellow wagtails fly towards intruder giving loud alarm calls.
There is no other group of bird species in The Netherlands where so much attention is given to the fate of eggs, as in meadow birds. For most people concerned, meadow bird success is nest success. For many people nest success is simply the proportion of nests hatched, out of a sample found. It has been known for a long time that this is not correct, and that nesting success should be expressed in terms of daily survival rates, based on so-called nest days. Each nest under observation yields one nest day for each day of observation. Thus, 3 nests observed during 4 days yield 12 nest days. The daily survival rate p is calculated as: p = a/(a+b), where a = total number of nest days in the sample, and b = number of nests lost. If a nest hatches during the observation period, the hatching day is counted as a nest day; the day on which a nest is predated not. The method is referred to as 'Mayfield method'. True hatching success is estimated as pL, where L = length of the incubation period (days). The standard deviation of p is: sd = sqrt((a-b) x b/a3).
To illustrate the method, a set of simulated nest records is given in table 1, based on p = 0.99 and L = 30. True hatching success is 74%. An observer visiting on day 15 will find 90 nests (10 have disappeared unnoticed), 74 of which hatch, yielding an apparent success of 88%. Using Mayfield, the same oberver would have found 76.5%, a much better estimate. Crude proportions of hatching gives also problems where different causes of loss are mutually exclusive. Table 5.2 summarizes simulation results for four data sets with two different predation levels, and with or without trampling losses, demonstrating that observed apparent proportions of nests hatched would lead to useless conclusions.
It is possible to convert old data on nesting succes to values corresponding to true daily survival rates, using the diagram designed by Green (fig. 5.1). If it is known how many days on average a successful nest has been under observation (meanobs), the number of nest days for the Mayfield formula can be estimated as follows: a = (number of successful nests)x(meanobs)+(number of unsuccessful nests)x(meanobs/2). Meanobs values for meadow birds are given in table 5.3 and 5.4.
It is not necesary to count all nest days exactly. Numbers of nest days can be estimated, assuming that observed nest loss (or hatching) always takes place half way the interval between the last two visits. Even when using very long intervals the error introduced is unimportant as compared to the error due to sample size. This is illustrated in Fig. 5.2. Several thousands of samples of varying sizes have been drawn from a very large set of simulated nest data with p = 0.99. From each of these samples p has been estimated, using the Mayfield formula. Fig. 5.2 shows the results, where all p values are given as a function of the number of nest days in each of the samples. This illustrates that very large sample sizes are required to obtain high levels of accuracy. In practice, this will never be the case. The lesson is that the wise observer should minimize the number of visits to nests already found, and to use his time to enlarge his sample size instead.
Expected hatching dates can be estimated using the floating characteristics of eggs during incubation. To standardize this method, the 'incubometer' has been designed (fig. 5.2). Fig 5.3 gives floating characteristics for lapwing and black-tailed godwit eggs.
The commonest cause of nest loss is predation. For meadow birds avian predators are most important. Daily survival rates are highest for species which hide their nests well (table 5.5). Predation pressure is highest at the beginning of the nesting season, and again at the end. During the peak of the season, predators are probably swamped by their prey, which reduces the probability of being preyed upon for each individual nest (fig. 5.5). Once every three or four years meadow birds suffer more predation than usual from small mustelids. Weasels and stoats follow the cyclic developments of vole populations, and after a vole crash they are forced to spend more energy on nest finding. This situation parallels the relationships between lemmings, arctic foxes and tundra birds in Siberia.
The secondmost important cause of nest loss in Dutch meadow birds is trampling by cattle. Like predation, this is best expressed in terms of daily survival rates, where the 'standard trampling value' v is the probabililty to survive one day grazing by animals in a density of one per hectare. The probability S to survive a period of grazing is: S = vLD, where L = length of grazing period, and D = density in animals per hectare. Basic trampling values for various grazing animals are given in table 5.6.
Because of problems with trampling, most meadow birds prefer fields to be mown as nest site. On the dairy farms of a group of farmers in Noord- Holland both bird densities and hatching success were higher on mown fields than on grazed fields (table 5.7). Figure 5.6 gives the average hatching dates for the most important meadow bird species in The Netherlands. Timing is not constant. In the course of the century, meadow birds have advanced their nesting by two weeks, following similar developments in grassland ecology, as a result of increased fertilization (fig. 5.7).
Impact of nest loss is difficult to assess, as most species commonly renest after loss. Especially in the lapwing replacement clutches are very common. To predict the breeding success per pair, a simulation model has been developed, taking renesting into account. In this way the effect of different grazing and mowing schemes can be predicted (fig. 5.8).
Chicks can adapt different strategies to grow up. The best known differen- ce is the difference between atricial and precocial birds. In altricial species, chicks are being fed by the parents, and they stay in the nest until fledging. Chicks spend little energy on thermoregulation and no energy at all on foraging, these tasks being taken care of by the parents. In precocial species, chicks leave the nest after hatching, and have to search their own food. Parents only serve to guard, and from time to time brood them. Thus, the parents spend much less energy, but the chicks much more. The energy expenditure of some meadow bird chicks, in comparison with various other organisms, is given in table 6.1.
There are many intermediate strategies between being altricial or precocial. Even within the precocial species there are differences. Lapwing chicks, for instance, grow relatively slowly, and depend during almost three weeks on brooding by their parents. Black-tailed godwit chicks, on the other hand, grow much faster, and are thermally indepentent from their parents at an age of nine days. Growth curves of some species are given in fig. 6.1.
Newborn chicks of both lapwing and black-tailed godwit need about five hours net foraging time per day to sustain growth. Time available for foraging is determined by the weather. In cold weather they have to be brooded bij their parents more often and during longer periods than in warm weather. While foraging, they also have to spend more energy on heat production themselves (fig. 6.2). Rain enhances the effect of the ambient temperature. Thus, in cold rainy weather chicks often find insufficient time to forage, and consequently loose weight, and eventually may die of starvation. When the chicks grow, they need less brooding (fig. 6.3). Also, the threshold temperature below which they do not to be brooded at all, rises with age (fig. 6.4).
Growth curves as in fig. 6.1, where growth parameters are given as a function of age, cannot be used for age determination. For this purpose one needs nomograms, where age is given as a function of for instance bill length (fig. 6.5). From age estimates of all chicks captured by ringers, one can calculate the distribution of birth dates (fig. 6.6).
The relationship between bill length and body weight can, with certain restrictions, be used as a measure for the condition of a chick. Condition can be expressed as the quotient of the observed weight over the expected weight, where the latter is the mean weight found for the bill length of the chick (standard weights, tabs. 6.2-6.5).
Table 6.6 gives a hypothetical sample of chicks of various ages caught by ringers. When many chicks die soon, relatively few large chicks will be caught. Years with relatively many large lapwing chicks coincide with years with much rain in May (fig. 6.7). In theory, the age distribution of chicks during the season could yield detailed information on chick survival. In practice however, there are too many statistical problems. Better information on survival can be obtained from age specific recoveries (table 6.7, fig. 6.8, and table 6.8).
Chicks mainly feed on insects living bavove the soil surface, or in the vegetation. Diets can be analysed from chitinous remains in the faeces (table 6.9). There are marked differences between species. Lapwing chicks mostly feed on surface dwelling beetles and larvae living in cow dung. black-tailed godwit chicks hunt for fast flying insects, which live in the upper strata of the vegetation. Redshanks are intermediate. Ruff chicks have a diet very similar to that of the black-tailed godwit. Oystercatcher chicks differ strongly, as they are being fed by their parents. They consume mostly tipulid larvae and earth worms.
Black-tailed godwit chicks start with a consumption of three insects per minute. When they grow, their intake rate increases (fig. 6.9). On a typical day, the intake rate starts at a high level, when chicks are hungry after the night. Rates are lowest during the middle of the day, and increase again towards sunset (fig. 6.10). It is argued that towards fledging a chick cannot survive on insects alone, as intake rates would have to increase to impossible levels. Chicks will then have to switch to more profitable prey, like tipulid larvae or earthworms (which are unavailable for small chicks, because their bills are too short). The point at which chicks may get trouble in catching enough insects may depend on the relative abundance of different size classes of insects present. This is also affected by management: with increasing levels of fertilization the average size of insects available decreases (fig. 6.11).
Meadow birds are not evenly distributed in The Netherlands. More than one third of the total populations are to be found in the province of Friesland alone. friesland shows a gradient in soil type, from heavy clay near the Wadden Sea to the peat areas in the southeast bordering the sandy elevations of the Drents Plateau. The transition zone of peat covered with clay is the richest in meadow birds. The clay zone is richest in nutrients, the peat zone poorest. Therefore, in theory meadow bird densities could be highest in the clay zone, and diminish towards the peat-sand border. However, agricultural intensity shows an opposite gradient, causing survival conditions for nests and families to increase from the clay zone towards the peat. The optimum is found in the transition zone (peat covered with clay). Table 7.1 gives characteristic densities on different soil types in Friesland, table 7.2 estimates of Frisian population sizes. Snipe and ruff have enormously decreased during the last decades (fig. 7.1).
Groningen is largely an arable province, with less grassland than Friesland. Also, many meadow birds are less strictly meadow birds, as they extensively use arable fields to nest. The best meadow bird grasslands are found in the southeast of the province, in the peaty areas surrounding the Leekstermeer. table 7.3 summarizes population sizes in Groningen, and the percentages nesting on arable land.
Drenthe is a predominantly sandy province, on high ground. Like in Groningen, many meadow birds in Drenthe are arable birds (table 7.4). 'True' meadow birds are mainly concentrated in small river valleys, and in the low lying peat area in the north, where the floodplain of many small rivers (notably the Drentse A system) meets the Leekstermeer area in Groningen.
In Overijssel, most meadow birds are concentrated in the old polders bordering the former IJsselmeer, and in the delta of the river IJssel. Concentrations locally occurr in the callows of the IJssel Valley. In the eastern part of the province most meadow birds have disappeared. Small concentrations in isolated moist spots only remain on a very local scale. Table 7.5 gives recent population estimates for Overijssel.
Like Overijssel has its best meadow bird areas in the polders bordering the former IJsselmeer. Polder Arkemheen is a fine example, where also on of the oldest meadow bird reserves of the Netherlands is situated (Table 7.6). Gelderland also has important meadow bird habitats along the large rivers Rijn and Waal, and in the low lying clay polders between the wto rivers. Table 7.7 summarizes characteristic densities in 95 sample areas.
The most renowned meadow bird area in Utrecht is the Eempolder. Early this century unbelievably high densities of ruff and redshank must have occurred, the ruff with 1500 females being the most numerous meadow bird! Black-tailed godwits were relatively scarce, becoming more numerous in the fourties and fifties, when for the first time became more numerous than the still very common, but rapidly decreasing redshank. Ruff populations had been decimated by then already. Recent estimates for the Eempolders are given in table 7.8. Strong decreases have also been noted in other polders (table 7.9).
Noord-Holland comes second after Friesland, as meadow bird province. So far, Noord-Holland is the only province where the steady decrease of meadow bird populations has been brought to a halt, as a result of special management in a large number of polders. There are a good many reserves, and in addition there are many areas under management agreements. Table 7.10 and 7.11 give characteristic densities, table 7.12 summarizes population estimates. The establishment of reserves does not always guarantee a postitive development of meadow bird populations. Figure 7.2 gives an example where nature management in a reserve first led to a considerable loss of populations, because fertilization had stopped to stimulate the development of interesting vegetations. Later, manuring was introduced again, leading to a restauration of population levels.
Zuid-Holland also has an example where a reserve, among other things created to preserve the corncrake, did not work (table 7.13). The area also suffered from the disappearance of the hydrological dynamics of the river and the former fresh-water estuary of the Biesbosch, after the closing of anti-flood barriers downstream. Zuid-Holland suffers from severe planological problems, because of the large concentration of big cities, which exert considerable pressure upon the remaining green areas. Table 7.14 summarizes population estimates of meadow birds.
Zeeland has only few meadow bird areas, most of the province being arable land, or estuarine habitats. As a consequence, black-tailed godwits are relatively scarce in Zeeland, while redshanks are common (table 7.15).
In Noord-Brabant meadow birds are rather sparsely distributed, but due to the large size of the province, total populations are still important. The increased adaptation of the lapwing to nesting in arable fields has caused a strong increase of this species in Noord-Brabant (table 7.16, 7.17). Black-tailed godwits used to nest on wet heath, but are now confined to a few low meadow areas, and the valleys of various small rivers.
Limburg has little importance for meadow birds (table 7.18). The development of black-tailed godwit populations exemplifies meadow bird development in general: first a widespread but sparse distribution in natural habitats (wet heath and moorland in the Peel), followed by a shift to agricultural grassland and an increase in population size, and finally total disappearance from the remaining bits of natural habitat and a strong decline in the agricultural land, due to over-intensification.
In the totally artificial IJsselmeerpolders planification left little room for meadow birds. A reserve of only 98 hectares, the Kievietslanden, has been established specifically for meadow birds. This has been very successful. In the first ten years populations soared to levels hitherto unknown in the Netherlands (fig. 7.3, table 7.19), but after a peak period, numbers gradually came down, to stabilise at much lower levels (but still high when compared to reserves elsewhere).
The distribution of meadow birds in Europe is greatly affected by two important climatic gradients. The first is the north south gradient in humidity and temperature development in spring. North of southern Scandinavia, meadows do not occur in large expanses on the European continent. South from the middle of France and southern Germany meadows look fine in winter and early spring, when they also attract large numbers of migrant lapwings, but towards the end of the spring they become hard and dry due to lack of rainfall or excessive evaporation, thus becoming unfit as nesting place for meadow birds. The optimum lies at British-Dutch-Ger- man latitudes.
The second gradient is the one running from the west of the British Isles east to eastern Poland and Russia. Along this gradient the climate changes from Atlantic to continental, making the occuurence of meadow bird meadows increasingly dependent on ground water. In the western half of Great Britain, wet meadows are not confined to lowland. Many lapwings and other waders are often 'upland birds'. East Anglia very much resembles The Netherlands and adjacent Northern Germany. In this area, wet meadows are more depending on ground water, and stay water-logged long enough during spring to maintain good properties for meadow birds. Further east, the denpendence on ground water increases, and in Eastern Germany (the former DDR) and Poland meadow birds become more and more dependent on low river valleys, and therefore increasingly local and scattered in their distribution. The 'meadow bird line' running east from the British Isles throught Holland, Northern Germany and Poland, loses itself in the forests of the northern part of the former Soviet Union.
A second 'meadow bird line' runs southeast from Germany, and Southeast Austria, into Hungary, towards the steppe region, a region of natural habitats for meadow birds. Due to the continental climate, the occurrence of meadow birds in the Hungarian puszta is more or less confined to the zones adjacent to surface waters. The steppe line can be continued outside Europe, via Southern Russia and Ukraine, into Asia.
The Asiatic steppe starts in the Europan part of Russia and Ukraine, in a belt just north of the Black Sea, then widening and running east north of the Caspian Sea, south of the Urals, into Southwestern Siberia. The West Siberian steppe, limited in the north by the taiga zone, ends in the foothills of the Altai Mountains. East of the moutains, the steppes reappear in Mongolia, to continue eastward just into the southeasternmost tip of Eastern Siberia. Thus, The Altai Mountains divide the Asiatic steppe into two main parts: the western part (Ukraine, Russia, Kazachstan, Southwest Siberia), and the eastern part (Mongolia, China, Southeast Siberia). The western part has been intensively cultivated over much of the area, resulting in great losses of habitats and birds. Expanses of relatively unspoilt grassland (rich in meadow birds in their natural habitat) are to be found in the Ural valley in northern Kazachstan, and between the Ob and the Irtysh in West Siberia, in the transition zone of the forest steppe. Bird faunas of the Asiatic steppe are still very similar to European meadow bird communities (table 9.1).
The climatic zones in the Asiatic steppe run mainly fron west to east. By contrast, zones in the North American prairie run from north to south, as a result of the gradient in precipitation caused by the great mountain ranges, intersecting the continent from north to south. In the east, the forests give way to half open parklands, and then to lush tallgrass prairie on fertile black soil. Further west, tall grasses become less dominant and short grasses take over. In the transition zone of mixed prairie, very rich mosaics of different vegatations are found. Still further west, the prairie becomes drier and poorer, and develops into true shortgrass steppe up to the foothills of the Rocky Mountains. Very little remains of the fertile tallgrass prairie, most of it having been converted into plowed arable. Relatively large tracts of shortgrass prairie remain intact, although the replacement of the bison by domestic cattle, and the extermination campaigns against small rodents have changed the habitat.
Although the main vegetation zones in the Nort American prairie run from north to south, most 'meadow birds' breed in a belt running from west to east through the northern prairies, as a result from the combination of precipiation and evaporation gradients, which cause southern prairies to become too dry for many species halfway the breeding season. The species composition in North America shows some differences with Europe and Asia, although the ecological groups are still very much the same (table 9.1, 9.2).
The South American pampa shows more differences. The true South American meadow bird is the southern lapwing (or chilean lapwing), which can be seen between Frisian cows in Argentinian pastures. South American meadows are very rich in small finches and buntings (table 9.3, 9.4). South Africa has only little temperate grassland, but has a number of interesting lapwings, and surprisingly many lark and pipit species (table 9.5).
Australia and New Zealand have little to offer in terma of meadow birds (table 9.6). The masked plover, a true lapwing, has developed as an agricultural bird in Australia, and has managed to colonise the New Zealand farmland on its own. In New Zealand it develops into a more genuine meadow bird than in its original homeland Australia.
Meadow birds have various migration strategies. Some species remain meadow bird all year round. Lapwing and snipe, for instance, not only nest in meadows, but also spend most of their time during migration and winter in wet grasslands or similar habitats.
A second category changes to estuarine habitats in winter. Oystercatcher and redshank migrate to coastal areas, to feed on tidal mudflats. They winter in the coastal areas of France, the British Isles, the Iberian Peninsula, and Morocco.
A third group migrates to fresh water habitats in subsaharan Africa. Black-tailed godwit, ruff, garganey, and yellow wagtail are species which concentrate in sahelian floodplains.
Although we usually associate the Sahel with drought, some of the world's largest wetlands are to be found here. Four large floodplain systems lie in the northern Sahel, just south of the Sahara: from west to east the delta of the Senegal River at the border of Senegal and Mauritania, the Inner Niger Delta in Mali, Lake Chad where Niger, Nigeria, Chad, and Cameroun meet, and the Sudd in southern Sudan (fig. 10.1).
The Sahelian floodplains are typically seasonal. The Senegal River and the Niger, for instance, carry large quantities of water during the rainy season (May-October) from the forested mountains of Guinea, northward into the dry Sahel. From August to November very large areas get flooded. From November onwards, the waters recede, leaving vegetated plains, mud, and shallow waters, on which cattle herds, farmers, fishermen, and northern migrant birds thrive.
For the Dutch populations of black-tailed godwit and ruff, the Senegal Delta (fig. 10.3) offers important winter quarters. The Djoudj National Park is renowned for its impressive concentrations of ruffs, roosting during the night, and garganey, which roost during the daytime. The birds feed in the surrounding rice fields.
The Senegal Delta has been drastically changed, due to dam construction. As a result, the area has lost much of its value for black- tailed godwits (table 10.1). The godwits now mostly winter further south, in the rice fields of Guinea Bissau (fig. 10.2, fig. 10.4).
After the breeding season, Dutch black-tailed godwits congregate in shallow waters, like the Oostvaardersplassen in Flevoland, where they feed on chironomid larvae. The adults migrate to Morocco in a single flight, the juveniles make stops in France, Portugal and Spain, on the way south. From Morocco all birds fly directly to the fresh water habitats in Senegal, ignoring the Mauritanian Banc d'Arguin, which is so important for many other wader species.
In January the birds already move north again, reaching their maximum in central Portugal in the second half of that month. In Portugal the birds concentrate in the Tagus Estuary (fig. 10.5). They roost on the tidal mudflats, but feed in the rice fields further inland (table 10.2). Godwits occurring in Portugal in January have been considered to be of Icelandic origin in the past, but rings show that they are in fact Dutch (table 10.3). However, on the Tagus mudflats they meet with Icelandic godwits, which stay there to feed.
Large numbers of black-tailed godwits occur in the Inner Niger Delta in Mali (fig. 10.6), although not many Dutch rings have been found. Many bird rings can be retrieved from local fishermen, who often carry them as ornaments (table 10.4). Most godwits wintering in Mali probably are of a more eastern origing as breeding birds (table 10.5).
When looking at the monthly distribution of recoveries of black- tailed godwits ringed as chicks in the Netherlands (table 10.6 and 10.7), it appears that after the first year the birds do not return to breed. They stay in Africa to summer, but recoveries are mysteriously missing. When looking at the age distribution of godwits found during spring migration in France and Italy (fig. 10.7), it seems that third calender year birds (two years of age) choose to return to the Netherlands via Italy, while older birds just migrate via France. This may indicate that the missing subadults spend their second summer (when they are one year old) in Mali, instead of Senegal or Guinea Bissau.
The snipe offers entirely different problems. Snipes pass through the Netherlands in large numbers from August to October, coming from Russia via Southern Sweden (fig. 10.8). Snipes are very conservative in their migration patterns, showing a high degree of site fidelity (fig. 10.9, table 10.8), which leads to a very uneven distribution of rings in the winter population. Danish rings are rarely seen in the Netherlands, while Duth rings are rarely seen in Denmark. Both categories are found in France. Apparently, on their way from the north and east to France, snipes choose to stop either in Denmark, or in the Netherlands, but never in both countries.
Snipes passing through the Netherlands used to stay put all summer, to moult. Very large numbers must have used the vast expanses of wet grasslands for this purpose, but this has occurred largely unnoticed, due to the dispersed occurrence of the species. Dutch meadows probably lost their significance as a moulting area for snipe, due to drainage. As a result, snipes have changed their migration pattern, and now moult in Great Britain and Northern France instead (fig. 10.10, table 10.9 and 10.10).
Migration patterns of ruff are much more diffuse than in black-tailed godwit or snipe. Ruff are extremely numerous in the subsaharan wetlands (table 10.13).
Every species has its own problem to offer: in the black-tailed godwit we have the mystery of the missing subadults in Africa, in the snipe the secret shift to other moulting areas, and in the ruff we have a problem with differential migration patterns of males and females. In Europe we see a predominance of males, but in Africa there are more females. However, if we combine sex ratios with winter numbers, millions of males are missing (table 10.14 and 10.15).
From calculated ring densities in bird populations, and numbers of rings returned by hunters, it is possible to make rough estimates of the number of birds shot (table 10.16-10.18).
There always have been controversies about how to deal with meadow bird protection. Some want to create sufficient reserves to harbour them all, as they see no future for them in our intensive agriculture. Others see a solution in a general decrease of intensity of the agricultural management, as they do not believe that sufficient reserves can ever be created to save all the birds. Those who want to separate birds and agriculture, and those who want to integrate them, have long been in debate. On the one hand, one cannot hope to create enough reserves to accomodate the very large populations of the more common species, like the black-tailed godwit. On the other hand, it will be impossible to lower agricultural intensity enough to create living conditions for sensitive species like ruff and snipe. In fact, one should not make a choice between separation and integration, but apply both methods, depending on location, birds present, and possibilities. Fig. 11.1 shows how different categories of natural values ask for different approaches in their management.
There are different ways to evaluate meadow bird populations. One can look at international importance (table 11.1), conform to the national Red List (table 11.3), or assign values according to scarcity or vulnerability. The latter was done to evaluate meadow bird areas for planological purpo- ses in the seventies (table 11.2), which after many changes and amendments eventually has lead to a national map of important meadow bird areas (fig. 11.2). Such methods have been regionally modified or adapted (table 11.4).
Since the seventies, many policy documents have appeared, with respect to the development of agriculture, landscape, and nature. Many of these documents have had effects on grassland management (table 11.5), and consequently on meadow birds, but in most cases the effects are difficult to trace. An exception is the Relatienota (1975), which offers the possibility for farmers to enter management agreements with the authorities, comparable to the ESA schemes in Britain. In the past, most effort was put into the creation of rerserves (fig. 11.3, table 11.6), but now the management agreement has taken a very important position. Creation of reserves now also takes place under the Relatienota. By the end of 1994, 19,354 ha reserves had been created under the Relatienota, and 36,465 ha had been brought under management agreements, involving 5218 farmers (table 11.7). The goal is to apply the Relatienota to 200,000 ha, in two phases, each involving 100,000 ha (table 11.8). Compensation levels under management agreements (by the end of 1994) range from Hfl. 180,- to Hfl. 1370,- per ha per annum, depending on the restrictions involved (table 11.9).
Outside protected areas, meadow bird nests can be individually protected by volunteers, by guarding them against mowing or trampling by cattle. Friesland has a long tradition in 'personal care' for meadow birds (fig. 11.4), and other provinces are now starting to follow the example (table 11.10).
Whichever management or protection method is chosen at any location, one should always aim at constant management forms at the lowest planological level: the parcel (plot) as management unit. Constant management leads to concentration of birds in the best spots, as a result from site fidelity, and the positive relationship between site fidelity and nesting success (fig. 11.5). Regular switching of good and bad management may destroy populations.
The best strategy to keep our meadow birds for the future is to diversify, and apply as many different methods and instruments as possi- ble, in a countrywide mosaic or network.
Copyright A.J. Beintema, February 1997