Ardea
Official journal of the Netherlands Ornithologists' Union

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Klomp H. (1954) De terreinkeus van de Kievit, Vanellus vanellus (L.). ARDEA 42 (1-2): 1-139
Habitat selection in the Lapwing, Vanellus vanellus (L.) I. Introduction 'This study is an attempt at an analysis of the factors governing the distribution of breeding Lapwings in the northern and western districts of the Netherlands. Some general questions are discussed first. On theoretical grounds the pattern of distribution within a certain region will be the result of two major influences: a. 'The selection of a habitat according to specific preferences (Lack 1933, 1937; Palmgren 1930; Moreau 1935). b. Local differences in reproduction and mortality. a. In the study of habitat selection two questions must be raised, which are often confused in literature: (1) which are the characters of the environment to which a bird responds (proximate factors), and (2) what is the survival value (biological significance) of the specific preference for certain habitats? An answer to the latter question may suggest what factors have favoured the selection of such preference in evolution {ultimate factors). Several authors have studied the biological significance of habitat preferences. 'Thus it has been found that the preference of a species for certain habitats is related to the fact that its structural properties or innate behaviour patterns would reduce its chance of survival in other habitats (Reinikainen1937; Palmgren 1932 a, 1932 b; Bergman 1946). In other cases settling in certain habitats results in protection against enemies (Errington 1934; Durango 1947), or, probably, prevention of competition with a closely related species (Lack 1944, 1947). On the other hand the proximate factors to which a bird reacts have rarely been investigated thoroughly. In general it is supposed that among these the properties of the vegetation play an important role. Detailed studies, however, are almost lacking and this is a serious handicap for a full explanation of distribution. b. Mortality and reproduction may also affect the pattern of distribution. For example, if in two habitats of equal attractiveness mortality or reproduction rate are different, density will not be the same in both. Thus the environmental factors may influence the distribution pattern in two ways, viz. through habitat selection and through mortality or reproduction. The present study deals mainly with the distribution of Lapwings in early spring, just after their arrival from the winter quarters in SW Europe. Census work revealed huge differences in density between one habitat and another (Sect. II). The question arises whether such differences are caused by habitat preferences or by mortality and reproduction. So far as these differences refer to habitats lying close together it is clear that they are the effect of habitat preferences, for in this case the thinly populated localities lie within reach of the birds which settle on the attractive spots. If, however, one compares densities in habitats which are farther apart, the influence of mortality and reproduction cannot be excluded at once. Nevertheless, it is probable that also in this case the differences in density are mainly the result of habitat preferences. There are two reasons for this assumption. Firstly, reproduction rate can be rejected as a possible cause of variation. The Lapwing invariably raises one clutch of four eggs and if its eggs are lost it produces repeat clutches until late in the season (Klomp 1951). Secondly, the birds inhabit the breeding grounds for only a short part of the year. During the other months they wander about. In this time the inhabitants of different parts of the Netherlands will intermingle freely. Hence, during most of the year there will be no systematic differences in mortality between the breeding birds of one district and another. Therefore, in my analysis of breeding densities I have at first assumed that these are the result of habitat preferences only. This led to an examination of the proximate factors in habitat selection (Sect. III A). In addition, I have investigated whether differences in mortality could explain the pattern of distribution, but the results were either negative or inconclusive (Sect. III B). Section IV deals with the survival value of the preference for certain habitats (see also Appendix). Finally, in section VI the causes of the recent decrease of the Lapwing in Holland are discussed. II. The distribution of the Lapwing; description of the sampling areas. The observations were made from 1946-1949. The distribution of the Lapwing was determined in two districts within the province of South-Holland (fig. 1 and 2). This was done by counting the ?? which are very conspicuous when making display flights on their territories (Brook 1911, Laven 1941, Rinkel 1940). For this reason, all population counts have been made during the period of intensive display, i.e. in the first hour after sunrise (fig. 3). The reliability of this method was checked by taking repeated census in the same area or by counting nests (fig. 4 and 5). Generally speaking, the Lapwing occurs on treeless grounds. It often nests in small plots of arable land amid grass-land, but it rarely occurs in extensive areas of the former. In grass-land density varies much. In the regions where the birds have been counted, the sampling areas 1 to 10 have been selected (see fig. 1 and 2). Ten more areas (11 to 20) situated outside these regions were added. These lay in the provinces of South-Holland, North-Holland and FryslGn. The size of these plots varied from 5.5 ha to 35 ha (Table 1). The areas 1-11 and 13-16 consisted of grass-land. Their fertility varied and depended on water level and manuring. Areas 5 and 11 were infertile grass-lands which had not been manured. Such 'natural grass-lands' have characteristic vegetation. If they are treated for some years with manure and fertilizer, they gradually change into 'transition grass-lands' with a vegetation of other grass species yielding a larger crop (areas 3, 8, 10, 13, 14, 15 and 16). If manuring is continued and, if necessary, the water level is lowered, fields that give large crops will be the result (areas 1, 2, 4, 6, 7 and 9). The areas 12, 18 and 20 are sandy plains in the dunes; 17 and 19 humid plains along the sea coast. The population density in these areas is summarized in Table 1, the water level and the type of soil of some areas in Table 6, the vegetation is described on pp. 62-64. III. The causes of the discontinuous distribution of the Lapwing A. Habitat selection. In the study of the proximate factors involved in habitat selection it was almost impossible to experiment. In general, I drew my conclusions from a critical examination of correlations between density figures and properties of the environment. In this way the influence of climate, food quality and quantity, type of soil, water level, and of height, density and other properties of the vegetation was studied. 1. Climate. The Lapwing stays on the breeding grounds only in spring. In this season the differences .in climatic factors are very slight and it is improbable that they influence habitat selection. 2. Food. The Lapwing collects its food from the surface of the fields; in doing so it is guided by visual stimuli. Observations by Collinge (1927), Madon (1935) and me have shown that the Lapwing feeds generally on earth worms and insects and less often on molluscs and spiders. The quantity of the soil fauna was determined in 8 sampling areas (Tables 2 and 3). By means of an earth drill 17-25 samples, each with a surface of 1 sq. dm and a depth of 5 cm, were taken in each area. Animals smaller than 3 mm were not collected. The tables show that there is no correlation between the distribution of the Lapwing and the abundance of food. The same was found in the Krim area (isle of Texel). This area consists of 4 parts. The soil fauna of the latter is summarized in Tables 4 and 5, whereas the distribution of the Lapwing is represented in fig. 6. The food quality is of no account either. Caged birds readily accepted all soil animals found in the grass-land areas 4, 7 and 9 where breeding Lapwings are lacking. Moreover, after the breeding season (from June to December) many Lapwings, searching for food, can be found in the grass-fields referred to (cf. fig. 1 and 2 with fig. 7). It follows that breeding distribution is not correlated with the amount of food. Breeding grounds where food is scarce are often densely populated. The inhabitants, however, very often feed far outside their territories (fig. 8, 9 and 10) and they lead their young to the nearest meadow which is rich in food. The breeding birds of areas that abound in food collect their meals in or near their territories and their families do not leave the area. An example are the observations in area 10 (for situation see fig. 1; for soil fauna see Tables 2 and 3; the positions of the Lapwings are shown in fig. 11 and 12). These observations show that feeding outside the breeding grounds is provoked by food scarcity. Yet poor fields are attractive breeding grounds. 3 and 4. The water level and the type of soil. In area 18 there is a satisfactory correlation between the water level and the positions of the Lapwing's nests (fig. 13). It could not be established whether or not this correlation was the expression of a causal relationship. In the other sampling areas, the water level of which was in all cases more than 10 cm below the surface, this factor did not influence the breeding density (Table 6 and fig. 14). The type of soil has been included in this table in view of differences in capillarity. The data of Table 6 suggest a preference for sand. A sandy soil, however, favours vegetation which is attractive to Lapwings (see below). Acidity of the soil is of no consequence (Table 7). 5. The slope and the altitude of the habitat have not been examined. 6. The height and the density of the vegetation. Fig. 15 shows the positions of the nests of Lapwings and Godwits in areas covered partly by high, partly by low vegetations. The height of the vegetations is given in Table 8 and fig. 22. Observations in area 4 and 5 (fig. 15) have shown that Lapwings never visit the high vegetation. They invariably alight in places where the vegetation is low and all pairing ceremonies are performed there. Only the display flight takes place over high and low vegetations indifferently. (Godwits do enter the high vegetation and the greater number of their nests is also found there.) In the areas 1, 2 and 4 (fig. 15) there are no differences in altitude, type of soil, water level and botanical composition between the parts with a low and those with tall vegetation. In areas 3 and 5 differences in level lead to differences in botanical composition (Tables 9 and 10). The latter differences, however, are small as compared with the variation among densely populated breeding grounds (see p. 129). Therefore they are not likely to be of account. Hence it seems a safe conclusion that Lapwings prefer low vegetations. This also appears from the position of the nests in fig. 16. In this area with high vegetation all Lapwings nest in those parts where the grass has been mown. Lapwing families with chicks likewise show a strong preference for low vegetations. Lapwings lay their eggs in April when the vegetation both in meadows and in hayfields is still low. By the time the eggs have hatched the grass in the hayfields has grown tall and the chicks born there are led to a meadow where vegetation is low. With the Godwit the reverse takes place (fig. 17). Fig. 18 illustrates the route of a female with chicks. The nest lies in a hayfield (plot 3). The male is in the meadow (plot 1). The female leads her chicks to the meadow across two ditches and plot 2. For the Lapwing dense vegetation becomes unacceptable when its height reaches a value of 4-7cm (cf. Table 8). In thinner vegetations a. greater height is tolerated. This appears from a series of observations in arable land. The crop (winter corn) on this field (8.5 ha) stood in thin rows that were 15 cm apart. The changes in the height of the vegetation are given in fig. 21, A and Table 11. The eggs of the Lapwings in this area were taken regularly in order to see at what height of the vegetation the birds would leave the spot. The number of territories was counted at regular intervals (Table 11). When the height of the crop reached 12 to 15 cm, the Lapwings left the area. This might be a result of the removal of the eggs but a control experiment in an area where the vegetation remained low disproves this. Here the birds did not leave although all eggs were taken away (Klomp 1951). In very thin vegetations a still greater height is accepted. This was found in two areas grown with young pine trees (fig. 19, 1 and 2). In both areas the trees were 75 cm apart. In area 1 the average height was 18 cm, in area 2 it was 38 cm. Lapwings bred in the former but not in the latter. The two areas lay side by side. Areas with taller trees scattered all over the field are not attractive. The areas 3 and 4 (fig. 19) were grown with pine trees and birches. The density of the trees in the two areas was the same but the height was different. The Lapwing avoided area 4. Again the fields lay side by side. Finally, fig. 15 illustrates breeding grounds the vegetation of which was about 20 cm high in some parts and lower in others. Here the parts with high vegetation were included in the territories. On the other hand, in fig. 20 the boundaries of territories coincide with the border between low vegetation and a 70 cm high one. If the surrounding vegetation is still taller the size of the area with low vegetation should be larger than about 5 ha. Otherwise, Lapwings will not settle there. Hence fields surrounded by avenues or other types of timber will be unattractive unless their surface exceeds 5 ha (see also Nicholson 1938/1939). 7. The ultimate height of the vegetation in grass-land. From the above it appears that the Lapwing prefers low vegetations. In the grass district of South-Holland, however, only part of the fields with low vegetation is accepted. Thus in this district there is no correlation between breeding density and the height of vegetation at the time of settling (Table 12, fig. 21 and 23). Neither did we find a relation between density of the vegetation and the Lapwing population (Table 12, fig. 24). But the height which the vegetation - if not grazed by cattle - reaches in the latter part of May proved to be an important factor. Fig. 25 shows a clear correlation between this 'ultimate height' (Fig. 22) and the breeding density of Lapwings. This dependency was not found in the Godwit (Table 12, fig. 26), and this will be discussed further below. In the Lapwing this correlation explains why large parts of South-Holland are very thinly populated (fig. 1 and 2). These are fertile regions where almost all fields have an excellent growth. The question now arises as to how this correlation is brought about with regard to the Lapwing. A first hypothesis implies a combined influence of mortality and attachment to the place of birth. We shall see that high vegetations probably increase the mortality of chicks. Hence it could be supposed that the inhabitants of vegetations with a great ultimate height produce very little offspring. As the Lapwing is rather faithful to its birthplace (Kraak cs. 1940), this would imply a very small immigration in spring, at least in those districts where fertile grass-fields prevail, e.g. in the+ centre of South-Holland. This hypothesis, however, is very improbable as it omits the important fact that also in the fertile districts about half of the fields are meadows in which the vegetation remains low throughout the season. As already stated, Lapwings lead their young to these meadows, thus avoiding the possible dangers of tall grass. Moreover, this hypothesis does not explain why Lapwings do not breed on fertile grass-lands in the immediate neighbourhood of heavily populated fields. Therefore, a much more reasonable hypothesis is the following. Already in early spring the Lapwing can distinguish the grass vegetations with a great ultimate height from those with a small .one. This would explain all the facts mentioned in this paragraph, and is supported by observations which are summarized in figs. 27 and 28. In two fertile areas a number of small infertile plots are included (A, B, C, D, and K, L, M, resp., cf. also fig. 22 and Table 13). Among the latter some were inhabited one year and others in other years. So the Lapwings did not nest in such a small plot because of their attachment to the place of birth or to the former breeding ground, but they selected these spots as a result of other factors. 8. The influence of the botanical composition. Now that we know the Lapwing makes a choice from the various grass-lands with low vegetation, the question arises to what character of the habitat the bird reacts. First, I have examined the botanical composition because it is related to the ultimate height of the vegetation. The occurrence of plant species has been expressed in frequency percentages according to De Vries (1937, 1948). No correlation, either positive or negative, could be found between the frequency of certain species of plants and the population density of the Lapwing (fig. 29). Furthermore, vegetations composed of very different plants constitute suitable breeding grounds. In areas with an equally dense population of Lapwings, quite different species of plants may predominate (see the list of plants found in the sampling areas, p. 64, group 3). The variation in the botanical composition of the areas with a moderate population density is not so great (p. 63, group 2). Finally, the vegetation of unoccupied grass-lands is rather uniform (p. 62, group 1, Table 14). The vegetations mentioned in Table 14 have one common feature in which they differ from those of all densely populated breeding areas. The former are green, whereas the latter are greyish brown. Thus the colour of the small plots of figs. 27 and 28 (see above) is clearly different from that of the surrounding green fields where Lapwings do not breed. This feature is already very conspicuous in early spring, when the Lapwing settles, whereas the differences in the ultimate height of the vegetation are not visible until much later. So in making a choice the Lapwing is probably guided by the colour of the fields. 9. The influence of changes in the appearance of grass-lands. The following observations give additional support to the conclusion reached in the last part of the preceding section. Fig. 30 shows an area partly consisting of transition grass-land (see p. 124 and Table 15). This meadow was not very attractive for the Lapwing. A strip of this field was sprayed with a solution of sodium chlorate, owing to which the grass died. Another part of the field was strewn over with cow-dung. As a result, the colour of both plots more or less approximated the colour of attractive fields. Moreover, the surface of the second plot was made uneven by the clots of dung. After this treatment 1 pair settled in the first plot and 8 in the second whereas the remaining part of the transition grass-land harboured no Lapwings at all. Fig. 31 is another example of the effect of strewing dung. These facts show that colour and roughness in combination strongly influence the attractiveness though, owing to the small size of the sprayed plot, it is impossible to separate their influence. 10. The breeding in arable land. Lapwings often nest in small plots of arable land amid grass-land. In large complexes of arable land they generally breed only on the edges and rarely in the centre (fig. 32). In early spring most of the arable land has low vegetation or is just or not yet sown. In general, therefore, these fields would seem to be suitable breeding grounds. Hence the non-occurrence in the centre of large complexes of arable land is a puzzling fact. Two hypotheses are put forward to explain this fact. 1. Lapwings only accept arable land if grass-land is present in the neighbourhood. 2. They are unable to build up a local population in arable land for the following reasons. In the course of the breeding season the crops grow higher, making the habitat unsuitable. From the centre of the complex, L3pwings with chicks can reach meadows only after crossing many ditches and long stretches of tall vegetation. Five times I observed that a Lapwing family was crossing a ditch with dense vegetation on the banks; 5 out of 18 chicks died in the attempt. So mortality was high and it seems probable that the Lapwing cannot maintain itself in the centre unless immigration takes place. Immigration, however, will be small owing to the strong attachment to the native ground or the old breeding area (Kraak C.S. 1940). At present it is impossible to make a choice between these two explanations. 11. The occurrence of other bird species does not affect the habitat selection of the Lapwing. 12. Summary of factors involved in habitat selection. The following factors increase the attractiveness of the habitat to Lapwings which seek a breeding place. a. Absence of scattered trees or high wood plantings on edges. b. A low vegetation or bare ground. c. A grey-brown to grey-green colour of the field and (or) an uneven surface. d. Proximity of the place of birth or the former breeding ground, respectively. B. The influence of reproduction and mortality 1. Differences in climatic factors between the sampling areas do not exist or are very small. The Lapwing can bear cold and wind very well. Chicks are most easily affected by rain, but the differences in precipitation between the areas are very small. So it is hardly possible that regional differences in mortality are caused by them. 2. Influence of the abundance of food. As already stated the breeding population of the Lapwing is generally denser in areas where food is scarce than in areas where it is abundant. It has not been investigated whether differences in food quantity involve differences in mortality. 3. Influence of predators. The mosaic distribution is not a consequence of local differences in predation. Lapwing and Godwit show very great differences in distribution although both species have the same mammal and avian enemies. Furthermore, low densities of Lapwings did not correlate with high densities of Carrion Crows, Kestrels and Magpies (Table 17). IV. The survival value of habitat preferences In order to study the survival value of habitat preferences in the Lapwing I compared this species with the Godwit. Unlike the Lapwing the latter species prefers high vegetations and accepts both green and greyish brown grass-lands. 1. The preference for low vegetations. In many respects this preference can be correlated with the Lapwing's organization. The Lapwing's locomotion is adapted to grounds without, or at most with low vegetation. The Godwit can also move in high vegetations. A detailed discussion of this difference is given in the Appendix. The Lapwing collects its food from the surface of the field and is guided by visual stimuli. The Godwit probes the ground with its long bill. In tall grass the range of vision is smaller than in low vegetations and this will affect the hunting success of the Lapwing. In the Godwit, however, the hunt for food will be as effective in high vegetations as in low ones. When alighting, the Lapwing holds its wings in a horizontal plane; the Godwit alights flapping its wings above its body. Parts of the Lapwing's pairing ceremonies fit in with a small height of vegetation. Its low flight during display and before coition would not be appropriate in a high vegetation. During the scrape ceremony the male displays the conspicuous feathers of coccyx and under tail, while the female stands at some distance. In tall grass this would be ineffectual. The Lapwing has an open nest and soon leaves it in case of danger. The brooding Godwit makes a cupola of grass blades over its nest and hides under it when alarmed. When guiding chicks, the Lapwing does not make for a look-out. It can inspect the field without doing so. The Godwit seeks a tree or pole from which it can survey the high vegetation. 2. The significance of the dislike for woods and forest borders in breeding Lapwings can be found in the greater offensive power of enemies in such wooded surroundings. From a series of observations on attacks by Carrion Crows and Magpies in open and wooded habitats it appears that, in the open field, the attacks of these predators were less dangerous to the brood from the following reasons: a. A greater part of the attacks are beaten off in the air and outside the territory. b. The duration of the attacks is much shorter. c. The crows need a longer flying time for each attack. d. Crows less often alight on the ground. e. The offensive power of the Lapwing is greatest in the air; on the ground it is considerably smaller, whereas predators in trees are seldom attacked. f. The crows cannot alight in trees or bushes, which they often do in more or less wooded country. When sitting in trees they are not only left alone by the attacking Lapwing, but they also can alight very easily on the ground near the nest. Hence, breeding in open fields most probably increases the survival of the offspring. The evolution of this preference, which is presumably inherited, may have been favoured by natural selection. 3. The assumed preference for brown and grey vegetations and for uneven surfaces. A brown or grey colour of the vegetation is correlated with a low ultimate height. Thus the Lapwing selects habitats which remain suitable throughout the breeding season (see above). The Godwit, on the other hand, does not prefer brown to green fields, which agrees with its preference for the high vegetations to which it is well adapted. The preference of the Lapwing possibly also has survival value because of a better camouflage of eggs and young. In fact the Lapwing often scrapes its nest on a spot where the eggs will match the environment. At first sight this hypothesis of camouflage is in contradiction with the fact that the Godwit, which has eggs closely resembling those of the Lapwing, often breeds in bright green vegetation. This species, however, builds a cupola over its nest and may therefore need a less perfect camouflage. Hence this objection is not serious and it remains doubtful whether camouflage is a factor in the function of habitat selection in the Lapwing. When the Lapwing leads chicks its dislike for bright green vegetations disappears. It then occurs in short grass of either type. In other words, as soon as the young are able to move, the parent birds respond to actual height instead of prospective height. This change in preference may have survival value as it enables the full exploitation of the food supply in the rich, fertile fields. V. General considerations. Nearly all characters of the habitat by which the Lapwing and presumably many other birds are guided in their choice are to be found in the structure of the vegetation and of the surface of the area. In other species of animals these characters can be quite different. Besides the structure of the bottom, Verwey (1949) also mentions temperature, light intensity and salinity of the water in connection with marine fish, molluscs and crustaceans. As regards insects it has been found that some species respond to similar characters as Lapwings and probably many other species of birds do (Smith C.S. 1949). In different bird species the biological significance of habitat preferences is often based on the same principles. It may be related to the structure of the locomotor apparatus and to the methods of feeding, nest building and escaping enemies. Unlike many other species, the Lapwing does not need cover, but chooses a habitat where attacks by predators can be beaten off most effectively. The relations between habitat preferences and food quantity in breeding birds have not been thoroughly analysed. In the Lapwing there is no positive correlation between population density and the supply of food. This holds good at least for the distribution of breeding birds.' Outside the breeding season the contrary is true and the birds tend to concentrate in places which are rich in food. VI. The decline of the Lapwing population in the Netherlands. The Lapwing is one of the most numerous grass-land birds in the Netherlands. In the last 30 years, however, its number has decreased in many parts of the country. The cause of this decrease was not clear, as various factors might have played a part. We mention egg-taking, the destruction of eggs and chicks by cattle and mechanical mowing and finally the kills of adults in the winter quarters (France, Spain, and Portugal). The influence of egg-taking and mechanical mowing has been examined before (Klomp 1951). Up to now these factors have not affected the Lapwing population very unfavourably. An important factor is the change brought about in the breeding grounds by the application of new methods of cultivation. In many parts of the Netherlands fertility of grass-land has been considerably improved during the last 30 years. A great deal of natural pasture, which was good Lapwing habitat but yielded bad crops, has been changed into productive grass-land, which is unattractive to Lapwings. In the writer's opinion this gradual disappearance of its favourite haunts is an important cause of the decline of the Lapwing. VII. Appendix. Terrestrial locomotion in the Lapwing and the Godwit 1. Analysis of locomotion. Stolpe (1932) has given a general analysis of terrestrial locomotion in birds. In fig. 35 a, the right leg pushes off from the ground, thereby moving the body forward. The body weight now rests on the left leg (fig. 35 b and c) but after phase d it is taken over by the right leg. Hence at every step the body weight is shifted from leg to leg. This is possible in two ways. 1. The moving free leg is placed in the median plane of the body (heron, stork). 2. The body is displaced and rotated laterally (duck). The pushing force is arbitrarily represented by K in fig. 36. The resultant of K and G (gravity) is R. The component K1 counterbalances G; the component R pushes the body forward. When the rate of movement is constant, R compensates the resultant of the frictions. The value of R - and therefore that of K - depends on the size of the steps. When the latter increases, K must also increase. If not, R would get a downward component, which is impossible. The force K is partly supplied by muscles originating caudally on the pelvis and inserting on the distal end of the femur, partly by the flexors of the toes. The energy required for propulsion equals the product of way-length and the average resultant of frictions. The latter comprise air-resistance (which probably may be omitted), friction between toes and surface at the moment that the free leg is placed on the ground, and friction in the joints. Furthermore at every step energy is needed for the rotation of the legs. After this general discussion the differences in locomotion of the Lapwing and the Godwit are considered. The Lapwing takes very long steps and runs; the Godwit, on the other hand, walks slowly taking short steps (fig. 34). This difference has been studied more closely by means of a cinematographic film. First the position of the centre of gravity was determined. According to Stolpe it lies in the vertical plane through the knee joints when the bird stands still. In fig. 37 this plane could be found from the proportion, which was measured in skeletons (Table 18). The centre of gravity is on v (fig. 37). During locomotion this line v will move in a horizontal direction. When seen from aside, the centre of gravity in the Godwit lies over the supporting area during the entire movement (or nearly so) of the free leg, as appears from fig. 38 B. This is due to the shortness of the steps and the large size of the supporting area (long toes), partly also to the movements of the neck (fig. 39). Moreover, in this species the body weight is shifted from leg to leg by placing the free moving leg in the median plane of the body (fig. 40 B). Apparently the centre of gravity always lies vertically over the supporting area. Thus the Godwit does not lose its balance when raising its free leg above the ground during locomotion. It therefore can spend relatively much time in moving its free leg forward. When walking in tall grass it raises this leg highly, folds its toes and bends them backward (fig. 41). In this way the toes are not caught in the grass. In the Lapwing on the other hand, the cen


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