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The effect of light on the choice of nests by domestic hens
Applied Animal Ethology, 11 (1983/84) 249-254 Elsevier Science Publishers B.V., Amsterdam -Printed
THE EFFECT HENS
249 in The Netherlands
OF LIGHT ON THE CHOICE OF NESTS BY DOMESTIC
MICHAEL C. APPLEBY, Agricultural Research (Ct. Britain) ‘Uniuersitat Hohenheim, (W. Germany)
HELEN E. McRAE and BEATE E. PEITZ’
Council’s Poultry Research Centre, Roslin, Midlothian EH25 9PS Institut fur Tierhaltung und Tierzuchtung,
Stuttgart
(Accepted for publication 14 December 1982)
ABSTRACT Appleby, M.C., McRae, H.E. and Peitz, B.E., 1984. The effect of light on the choice of nests by domestic hens. Appl. Anim. Ethol., 11: 249-254. The involvement of light in nest-site selection by domestic fowls was tested in two strains of laying hens at two stages of maturity. Individuals that were about to lay an egg were isolated in a pen and given a choice of two sorts of nest-box, one illuminated internally and the other without illumination. Nearly all birds tested laid in one of the boxes provided, but their choice of dark or light conditions varied strongly with both strain and maturity. Only one of the four categories of hen, those of a White Leghorn strain laying their first egg, exhibited the expected preference for dark nests. Birds of a strain derived from Rhode Island Reds were more likely to lay in light nests, and with both strains hens which had previously been laying in open pens showed greater preference for light nests than did naite individuals. These results suggest that light intensity is not a fundamental factor influencing nest-site selection, hut it may nevertheless haveto be considered in the management of laying hens.
INTRODUCTION
In the commercial management of domestic fowls, a feature common to all systems of housing for laying hens, except battery cages, is the collection of eggs from nest-boxes, and a major problem with such systems has been the failure of some birds to use the nests provided. The behaviour of hens in choosing where they will lay their eggs is therefore of economic importance. However, little is known about the factors that influence this behaviour. Only one such factor, the light intensity at a possible nest-site, has been considered frequently, and the limited evidence available on the importance of this factor is conflicting (see Discussion). The effect of light on the choice of nests by domestic hens is considered in detail here. General texts on the management of poultry usually suggest that hens prefer to lay in dark places (e.g. Robinson, 1948; Winter and Funk, 1951;
0304-3762/84/$03.00
0 1984 Elsevier Science Publishers B.V.
250
Card and Nesheim, 1966), but offer no supporting evidence for this suggestion. It is not clear why light intensity should be involved in the choice of a nest-site, unless hens associate it with other factors, such as enclosure and protection. Most galliform species, including hens, make only a simple nestscrape on the ground (Thomson, 1964), and protection of the eggs depends mostly on the cryptic nature of nest-sites chosen (Wood-Gush, 1975). Domestic fowls conceal their nests when in the feral state (Duncan et al., 1978), and they might be expected to attempt to behave similarly in captivity, by laying in enclosed, protected places. Such places would frequently be darker than their surroundings, so we predicted that if hens had a choice of enclosed places in which to lay, they would select dark rather than light ones. This behaviour may well be affected by experience (cf. Wood-Gush and Murphy, 1970), and may also differ between strains, since strains are known to vary in other aspects of pre-laying behaviour (Wood-Gush, 1972). We therefore tested the prediction in two strains of domestic fowl at two stages of maturity. METHODS
Nest-choice was tested experimentally in two strains of domestic hen, White (derived from White Leghorns) and Brown (a commercial Rhode Island Red hybrid). Four groups of hens, of between 9 and 14 birds, were kept on litter in pens measuring 280 X 280 cm. The pens were illuminated for 14 h each day by ceiling lights, which produced a light intensity of approximately 30 lux in the centre of each pen. One group of each strain (“pullets”) was then tested from the onset of laying, while another (“mature hens”) was allowed to lay on the floor for a period before testing. Subjects were palpated daily to detect the presence of a hard-shelled egg in the oviduct, and those ready to lay were identified by observation of their behaviour (Wood-Gush, 1975). Nest-choice was then investigated by isolating a bird in a test-pen, similar to the holding-pens except that it contained 4 nest-boxes. The nest-boxes used were the bottom tier of a standard double set of wooden boxes, placed on the floor against one side of the pen. Two of the nests were illuminated, at about 40 lux, by placing 15 W bulbs in the roof of the upper tier. Light intensity in the other nests was about 5 lux. The upper boxes were closed at the front, but open at the back for ventilation, and floored with two layers of frosted perspex with an air gap between to prevent conduction of heat from the bulbs to the lower boxes. The effect of radiation on the temperature of lit boxes was also slight, being at most only 0.5”C higher than unlit boxes. Lit and unlit boxes were arranged alternately, giving a pattern of either light, dark, light, dark or dark, light. When an egg had been laid, its position was recorded and the hen and egg were removed. Litter from different nest-boxes was then mixed to make the olfactory conditions of each box similar for the next hen to be tested. The first choice made by each hen was noted for all 4 groups. In addition, for 3
251
groups, isolation of as many hens as possible continued for as many eggs as possible, until they had made the same choice often enough to be significant by sign test (Siegel, 1956). The order of lit and unlit boxes was changed at least once during this period, so these established choices were for light or dark conditions rather than for particular boxes. RESULTS
Nearly all the hens tested laid in the nest-boxes provided, rather than on the floor, from their first test. These included every hen that was isolated while laying her first egg (Table I). Even among hens used to laying on the floor, 78% used nests when they first encountered them (11 out of 14 White and 7 out of 9 Brown), and only one individual (a mature, White hen) continued to lay on the floor repeatedly. Most hens isolated several times soon established a consistent choice for either light or dark conditions, only one hen in each group failing to do so (Table I). TABLE I Choice between dark and light nest-boxes Strain
White White Brown Brown
Maturity
Pullets Mature hens Pullets Mature hens
First choice
Established choice
N
Dark Light
N
12 14 14 9
12 6 4 1
7 12 12 -
0 I 10 8
Dark Light 6 2 7
0 9 4
Variation in nest-choice between birds of different groups could mostly be accounted for by the 2 factors of strain and maturity; an analysis of deviance between groups (D. Waddington, personal communication, 1982) using an additive, log-linear model (Everitt, 1977) for these factors showed that residual variation was not significant. The effects of strain and maturity are discussed separately below. Differences between strains At both stages of maturity studied, birds of the White strain were more likely to lay in dark nest-boxes than were those of the Brown strain (Fig. 1, P < 0.001 by analysis of deviance). Among hens laying their first egg, all 12 of the White strain chose dark nest-boxes (sign test, P < O.OOl), but only 4 of the 14 Brown birds did so (sign test, NS), and the naive choices of the 2 strains differed significantly (Fisher’s exact probability test, P < 0.01). However, while White hens were consistent in their subsequent choices (6 of
252
them confirmed their preference for dark nests; sign test, P < 0.05), some Brown birds which had laid first in the light later laid in the dark (Table I), and the established choices of the 2 groups were not significantly different (by Fisher’s test). lOO%Dark preference 50%-
La
Light preference 100% No.
12 Pullets
Mature
9
14
13 hens
WHITE
Pullets
Mature
hens
BROWN
Fig. 1. Choice between dark and light nest-boxes.
Mature hens of the White strain showed no clear choice for dark or light (sign test, NS), but most of the Brown strain laid in the light (sign test, P < 0.05), although this difference was not statistically significant (by Fisher’s test). Variation with maturity Hens that had been laying previously in the holding-pens were more likely to choose illuminated nest-boxes than dark ones. This tendency was stronger than in birds just beginning to lay, in both strains considered (Fig. 1, P < 0.01 by analysis of deviance). The first choice made by individuals of the White strain differed significantly between pullets and mature hens (Fisher’s test, P < 0.01). Furthermore, variation with maturity was also noted within the mature group: individuals that laid in light nest-boxes had generally been laying in the holding-pen for longer (median 62 days) than those that laid in dark boxes (median 47 days; Fig. 2), although not significantly so (Mann-Whitney U test, P < 0.2). In addition, more of the mature hens established a preference for light nests (9 out of 11; sign test, P < 0.1) than had laid their first egg in the light, and the difference between the 2 groups was then even more marked (Table I; Fisher’s test, P < 0.01). Similarly, although both groups of hens of the Brown strain tended to choose illuminated nests, the trend was stronger in the mature birds than in
253
Laid in dark nest
??
Laid in light nest
?? ??
0
I
I
30
40
0
?? ??
00000
+,
0
.+
50
60
4
70
80
Maturity Fig. 2. Variation
(days since first egg) in choice among mature, White hens. The arrows indicate medians.
the narve ones, and only significant in the mature group (see above). Variation with maturity was not, however, significant in this strain (by Fisher’s test). DISCUSSION
The effect of illuminating nest-boxes on their selection by hens in isolation varied in this study depending on the strain and maturity of the hens involved. As a result, only 1 of 4 groups tested exhibited the predicted preference for dark places to lay. The reasons why strain and maturity affected the results in this way are not clear, but it may nevertheless be important to take these factors into account in the management of laying hens. In two different strains of hens studied, mature birds which had been laying in open pens were more likely to choose illuminated nest-boxes in which to lay than were pullets laying their first eggs. This may be explained by a preference for the lighting conditions of which they already had experience: in one strain, variability in choice was related to the length of their previous experience of laying in pens. Similarly, a study of Brown Leghorns showed that hens used to laying in dark nest-boxes preferred dark nests subsequently, in contrast to naive pullets (Wood-Gush and Murphy, 1970). However, it is important that all but one of the mature birds in the present study quickly started using nest-boxes when given the opportunity to do so, in spite of being used to laying on the floor. These results suggest that while variation in lighting may affect which nest-boxes are chosen, it is not a fundamental factor determining their use by solitary individuals. The basic physical characteristics of nest-sites sought by domestic hens are being investigated in work still in progress. In spite of the above conclusions, it is possible that in different social conditions from those used in this study, lighting may also affect whether some hens actually use nest-boxes at all, or lay on the floor. Dorminey
254
(1974) found that groups of White Leghorns laid more eggs on the floor when boxes were placed opposite a light rather than under it, or when general light levels were decreased. In commercial systems with nest-boxes, hens will be in groups, not in isolation, and so the arrangement of nests with respect to light may be of importance in the management of such systems (as suggested by Dorminey’s results). If so, the variation in behaviour between strains demonstrated here should also be taken into account. Although individuals of a light, white strain chose dark nest-boxes, at least when inexperienced at laying, hens of a heavier, brown strain tended to choose light boxes. This variation may account for the contrasting results of previous studies which used different strains (Woods and Laurent, 1958; Wood-Gush and Murphy, 1970; Dorminey, 1974). Strains have also been shown to vary in other aspects of behaviour, including pre-laying behaviour (Wood-Gush, 1972) but the reasons for this variation between lines selected artificially for other characteristics (Wood-Gush, 1959) remain unclear. ACKNOWLEDGEMENTS
We wish to thank Dr. Ian Duncan and other members of the Poultry Research Centre for helpful discussion. The project was financed by a grant from the Commission of the European Communities to the Agricultural Research Council. REFERENCES Card, L.E. and Nesheim, M.C., 1966. Poultry Production. 10th edn., Lea and Febiger, Philadelphia, 400 pp. Dorminey, R.W., 1974. Incidence of floor eggs as influenced by time of nest installation, artificial lighting and nest location. Poult. Sci., 53: 1886-1891. Duncan, I.J.H., Savory, C.J. and Wood-Gush, D.G.M., 1978. Observations on the repro3 ductive behaviour of domestic fowl in the wild. Appl. Anim. Ethol., 4: 29-42. Everitt, B.S., 1977. The Analysis of Contingency Tables. Chapman and Hall, London, 128 pp. Robinson, L., 1948. Modern Poultry Husbandry, Lockwood, London, 522 pp. Siegel, S., 1956. Nonparametric Statistics for the Behavioural Sciences. McGraw-Hill Kogakusha, Tokyo, 312 pp. Thomson, A.L. (Editor), 1964. A New Dictionary of Birds. The British Ornithologists’ Union/Nelson, London, 928 pp. Winter, A.R. and Funk, E.M , 1951. Poultry Science and Practice. Lippincott, New York, 662 pp. Wood-Gush, D.G.M., 1959. A history of the domestic chicken from antiquity to the 19th Century. Poult. Sci., 38: 321-326. Wood-Gush, D.G.M., 1972. Strain differences in response to sub-optimal stimuli in the fowl. Anim. Behav., 20: 72-76. Wood-Gush, D.G.M., 1975. Nest construction by the domestic hen : some comparative and physiological considerations. In: P. Wright, P.G. Caryl and D.M. Vowles (Editors), Neural and Endocrine Aspects of Behaviour in Birds. Elsevier, Amsterdam, pp. 35-49. Wood-Gush, D.G.M. and Murphy, L.B., 1970. Some factors affecting the choice of nests by the hen. Br. Poult. Sci., 11: 415-417. Woods, R.E. and Laurent, C.K., 1958. A note of nest preference. Poult. Sci., 37: 14611462.
THE EFFECT HENS
249 in The Netherlands
OF LIGHT ON THE CHOICE OF NESTS BY DOMESTIC
MICHAEL C. APPLEBY, Agricultural Research (Ct. Britain) ‘Uniuersitat Hohenheim, (W. Germany)
HELEN E. McRAE and BEATE E. PEITZ’
Council’s Poultry Research Centre, Roslin, Midlothian EH25 9PS Institut fur Tierhaltung und Tierzuchtung,
Stuttgart
(Accepted for publication 14 December 1982)
ABSTRACT Appleby, M.C., McRae, H.E. and Peitz, B.E., 1984. The effect of light on the choice of nests by domestic hens. Appl. Anim. Ethol., 11: 249-254. The involvement of light in nest-site selection by domestic fowls was tested in two strains of laying hens at two stages of maturity. Individuals that were about to lay an egg were isolated in a pen and given a choice of two sorts of nest-box, one illuminated internally and the other without illumination. Nearly all birds tested laid in one of the boxes provided, but their choice of dark or light conditions varied strongly with both strain and maturity. Only one of the four categories of hen, those of a White Leghorn strain laying their first egg, exhibited the expected preference for dark nests. Birds of a strain derived from Rhode Island Reds were more likely to lay in light nests, and with both strains hens which had previously been laying in open pens showed greater preference for light nests than did naite individuals. These results suggest that light intensity is not a fundamental factor influencing nest-site selection, hut it may nevertheless haveto be considered in the management of laying hens.
INTRODUCTION
In the commercial management of domestic fowls, a feature common to all systems of housing for laying hens, except battery cages, is the collection of eggs from nest-boxes, and a major problem with such systems has been the failure of some birds to use the nests provided. The behaviour of hens in choosing where they will lay their eggs is therefore of economic importance. However, little is known about the factors that influence this behaviour. Only one such factor, the light intensity at a possible nest-site, has been considered frequently, and the limited evidence available on the importance of this factor is conflicting (see Discussion). The effect of light on the choice of nests by domestic hens is considered in detail here. General texts on the management of poultry usually suggest that hens prefer to lay in dark places (e.g. Robinson, 1948; Winter and Funk, 1951;
0304-3762/84/$03.00
0 1984 Elsevier Science Publishers B.V.
250
Card and Nesheim, 1966), but offer no supporting evidence for this suggestion. It is not clear why light intensity should be involved in the choice of a nest-site, unless hens associate it with other factors, such as enclosure and protection. Most galliform species, including hens, make only a simple nestscrape on the ground (Thomson, 1964), and protection of the eggs depends mostly on the cryptic nature of nest-sites chosen (Wood-Gush, 1975). Domestic fowls conceal their nests when in the feral state (Duncan et al., 1978), and they might be expected to attempt to behave similarly in captivity, by laying in enclosed, protected places. Such places would frequently be darker than their surroundings, so we predicted that if hens had a choice of enclosed places in which to lay, they would select dark rather than light ones. This behaviour may well be affected by experience (cf. Wood-Gush and Murphy, 1970), and may also differ between strains, since strains are known to vary in other aspects of pre-laying behaviour (Wood-Gush, 1972). We therefore tested the prediction in two strains of domestic fowl at two stages of maturity. METHODS
Nest-choice was tested experimentally in two strains of domestic hen, White (derived from White Leghorns) and Brown (a commercial Rhode Island Red hybrid). Four groups of hens, of between 9 and 14 birds, were kept on litter in pens measuring 280 X 280 cm. The pens were illuminated for 14 h each day by ceiling lights, which produced a light intensity of approximately 30 lux in the centre of each pen. One group of each strain (“pullets”) was then tested from the onset of laying, while another (“mature hens”) was allowed to lay on the floor for a period before testing. Subjects were palpated daily to detect the presence of a hard-shelled egg in the oviduct, and those ready to lay were identified by observation of their behaviour (Wood-Gush, 1975). Nest-choice was then investigated by isolating a bird in a test-pen, similar to the holding-pens except that it contained 4 nest-boxes. The nest-boxes used were the bottom tier of a standard double set of wooden boxes, placed on the floor against one side of the pen. Two of the nests were illuminated, at about 40 lux, by placing 15 W bulbs in the roof of the upper tier. Light intensity in the other nests was about 5 lux. The upper boxes were closed at the front, but open at the back for ventilation, and floored with two layers of frosted perspex with an air gap between to prevent conduction of heat from the bulbs to the lower boxes. The effect of radiation on the temperature of lit boxes was also slight, being at most only 0.5”C higher than unlit boxes. Lit and unlit boxes were arranged alternately, giving a pattern of either light, dark, light, dark or dark, light. When an egg had been laid, its position was recorded and the hen and egg were removed. Litter from different nest-boxes was then mixed to make the olfactory conditions of each box similar for the next hen to be tested. The first choice made by each hen was noted for all 4 groups. In addition, for 3
251
groups, isolation of as many hens as possible continued for as many eggs as possible, until they had made the same choice often enough to be significant by sign test (Siegel, 1956). The order of lit and unlit boxes was changed at least once during this period, so these established choices were for light or dark conditions rather than for particular boxes. RESULTS
Nearly all the hens tested laid in the nest-boxes provided, rather than on the floor, from their first test. These included every hen that was isolated while laying her first egg (Table I). Even among hens used to laying on the floor, 78% used nests when they first encountered them (11 out of 14 White and 7 out of 9 Brown), and only one individual (a mature, White hen) continued to lay on the floor repeatedly. Most hens isolated several times soon established a consistent choice for either light or dark conditions, only one hen in each group failing to do so (Table I). TABLE I Choice between dark and light nest-boxes Strain
White White Brown Brown
Maturity
Pullets Mature hens Pullets Mature hens
First choice
Established choice
N
Dark Light
N
12 14 14 9
12 6 4 1
7 12 12 -
0 I 10 8
Dark Light 6 2 7
0 9 4
Variation in nest-choice between birds of different groups could mostly be accounted for by the 2 factors of strain and maturity; an analysis of deviance between groups (D. Waddington, personal communication, 1982) using an additive, log-linear model (Everitt, 1977) for these factors showed that residual variation was not significant. The effects of strain and maturity are discussed separately below. Differences between strains At both stages of maturity studied, birds of the White strain were more likely to lay in dark nest-boxes than were those of the Brown strain (Fig. 1, P < 0.001 by analysis of deviance). Among hens laying their first egg, all 12 of the White strain chose dark nest-boxes (sign test, P < O.OOl), but only 4 of the 14 Brown birds did so (sign test, NS), and the naive choices of the 2 strains differed significantly (Fisher’s exact probability test, P < 0.01). However, while White hens were consistent in their subsequent choices (6 of
252
them confirmed their preference for dark nests; sign test, P < 0.05), some Brown birds which had laid first in the light later laid in the dark (Table I), and the established choices of the 2 groups were not significantly different (by Fisher’s test). lOO%Dark preference 50%-
La
Light preference 100% No.
12 Pullets
Mature
9
14
13 hens
WHITE
Pullets
Mature
hens
BROWN
Fig. 1. Choice between dark and light nest-boxes.
Mature hens of the White strain showed no clear choice for dark or light (sign test, NS), but most of the Brown strain laid in the light (sign test, P < 0.05), although this difference was not statistically significant (by Fisher’s test). Variation with maturity Hens that had been laying previously in the holding-pens were more likely to choose illuminated nest-boxes than dark ones. This tendency was stronger than in birds just beginning to lay, in both strains considered (Fig. 1, P < 0.01 by analysis of deviance). The first choice made by individuals of the White strain differed significantly between pullets and mature hens (Fisher’s test, P < 0.01). Furthermore, variation with maturity was also noted within the mature group: individuals that laid in light nest-boxes had generally been laying in the holding-pen for longer (median 62 days) than those that laid in dark boxes (median 47 days; Fig. 2), although not significantly so (Mann-Whitney U test, P < 0.2). In addition, more of the mature hens established a preference for light nests (9 out of 11; sign test, P < 0.1) than had laid their first egg in the light, and the difference between the 2 groups was then even more marked (Table I; Fisher’s test, P < 0.01). Similarly, although both groups of hens of the Brown strain tended to choose illuminated nests, the trend was stronger in the mature birds than in
253
Laid in dark nest
??
Laid in light nest
?? ??
0
I
I
30
40
0
?? ??
00000
+,
0
.+
50
60
4
70
80
Maturity Fig. 2. Variation
(days since first egg) in choice among mature, White hens. The arrows indicate medians.
the narve ones, and only significant in the mature group (see above). Variation with maturity was not, however, significant in this strain (by Fisher’s test). DISCUSSION
The effect of illuminating nest-boxes on their selection by hens in isolation varied in this study depending on the strain and maturity of the hens involved. As a result, only 1 of 4 groups tested exhibited the predicted preference for dark places to lay. The reasons why strain and maturity affected the results in this way are not clear, but it may nevertheless be important to take these factors into account in the management of laying hens. In two different strains of hens studied, mature birds which had been laying in open pens were more likely to choose illuminated nest-boxes in which to lay than were pullets laying their first eggs. This may be explained by a preference for the lighting conditions of which they already had experience: in one strain, variability in choice was related to the length of their previous experience of laying in pens. Similarly, a study of Brown Leghorns showed that hens used to laying in dark nest-boxes preferred dark nests subsequently, in contrast to naive pullets (Wood-Gush and Murphy, 1970). However, it is important that all but one of the mature birds in the present study quickly started using nest-boxes when given the opportunity to do so, in spite of being used to laying on the floor. These results suggest that while variation in lighting may affect which nest-boxes are chosen, it is not a fundamental factor determining their use by solitary individuals. The basic physical characteristics of nest-sites sought by domestic hens are being investigated in work still in progress. In spite of the above conclusions, it is possible that in different social conditions from those used in this study, lighting may also affect whether some hens actually use nest-boxes at all, or lay on the floor. Dorminey
254
(1974) found that groups of White Leghorns laid more eggs on the floor when boxes were placed opposite a light rather than under it, or when general light levels were decreased. In commercial systems with nest-boxes, hens will be in groups, not in isolation, and so the arrangement of nests with respect to light may be of importance in the management of such systems (as suggested by Dorminey’s results). If so, the variation in behaviour between strains demonstrated here should also be taken into account. Although individuals of a light, white strain chose dark nest-boxes, at least when inexperienced at laying, hens of a heavier, brown strain tended to choose light boxes. This variation may account for the contrasting results of previous studies which used different strains (Woods and Laurent, 1958; Wood-Gush and Murphy, 1970; Dorminey, 1974). Strains have also been shown to vary in other aspects of behaviour, including pre-laying behaviour (Wood-Gush, 1972) but the reasons for this variation between lines selected artificially for other characteristics (Wood-Gush, 1959) remain unclear. ACKNOWLEDGEMENTS
We wish to thank Dr. Ian Duncan and other members of the Poultry Research Centre for helpful discussion. The project was financed by a grant from the Commission of the European Communities to the Agricultural Research Council. REFERENCES Card, L.E. and Nesheim, M.C., 1966. Poultry Production. 10th edn., Lea and Febiger, Philadelphia, 400 pp. Dorminey, R.W., 1974. Incidence of floor eggs as influenced by time of nest installation, artificial lighting and nest location. Poult. Sci., 53: 1886-1891. Duncan, I.J.H., Savory, C.J. and Wood-Gush, D.G.M., 1978. Observations on the repro3 ductive behaviour of domestic fowl in the wild. Appl. Anim. Ethol., 4: 29-42. Everitt, B.S., 1977. The Analysis of Contingency Tables. Chapman and Hall, London, 128 pp. Robinson, L., 1948. Modern Poultry Husbandry, Lockwood, London, 522 pp. Siegel, S., 1956. Nonparametric Statistics for the Behavioural Sciences. McGraw-Hill Kogakusha, Tokyo, 312 pp. Thomson, A.L. (Editor), 1964. A New Dictionary of Birds. The British Ornithologists’ Union/Nelson, London, 928 pp. Winter, A.R. and Funk, E.M , 1951. Poultry Science and Practice. Lippincott, New York, 662 pp. Wood-Gush, D.G.M., 1959. A history of the domestic chicken from antiquity to the 19th Century. Poult. Sci., 38: 321-326. Wood-Gush, D.G.M., 1972. Strain differences in response to sub-optimal stimuli in the fowl. Anim. Behav., 20: 72-76. Wood-Gush, D.G.M., 1975. Nest construction by the domestic hen : some comparative and physiological considerations. In: P. Wright, P.G. Caryl and D.M. Vowles (Editors), Neural and Endocrine Aspects of Behaviour in Birds. Elsevier, Amsterdam, pp. 35-49. Wood-Gush, D.G.M. and Murphy, L.B., 1970. Some factors affecting the choice of nests by the hen. Br. Poult. Sci., 11: 415-417. Woods, R.E. and Laurent, C.K., 1958. A note of nest preference. Poult. Sci., 37: 14611462.