Patterns of Comfort Behaviour and Activity in Domestic Fowls: A Comparison between Cages and Pens

Hr. vet.]. (1974), 130, 23

PATTERNS OF COMFORT BEHAVIOUR AND ACTIVITY IN DOMESTIC FOWLS: A COMPARISON BETWEEN CAGES AND PENS By

A.

J.

BLACK AND B.

O.

HUGHES

A.R.C. Poultry Research Centre, Edinburgh SUMMARY

The incidence of nine behaviour patterns in three strains of bird housed in cages or pens was compared. There were few strain differences, but wing flapping, movement flapping, dust bathing and ground scratching were more frequent in pens than in cages, whereas head shaking, preening, and wing/leg stretching were more frequent in cages. Transferring groups of birds between cages and pens resulted in significant changes in the incidence of the first five behaviours noted above; the changes were in the predicted direction. Birds in cages were generally less active than those in pens, but spent more time feeding and drinking. The findings cqnfirm that caging leads to considerable quantitative changes in patterns of behaviour. Physical constraints may play an important part, since the behaviour patterns are latent and can be released by transfer to a more spacious environment; there is, however, a suggestion that other factors may be important in the long term. INTRODUCTION

Although the close restraint of hens in battery cages has a marked effect on their behaviour (Ewbank, 1969; Levy, 1944), few quantitative studies have been carried out to assess these changes. Bareham (1972) found that, in a comparison between hens housed in cages or on deep litter, the caged birds spent less time pecking, turning and in reflex activity, but more time in feeding and head flicking than did birds on deep litter. In this paper we survey, on an ontogenetic basis, the incidence of nine behaviour patterns in three strains of domestic fowl housed in groups in cages or on deep litter. Some observations were also made of their general activity. MATERIALS AND METHODS

Experiment

I

Three strains of laying bird, Thornber 808, Thornber 909 and Shaver 288, were housed at day old in groups of seven in cages 0.41 X 0·35 m and in groups of eight in p ens (2 ·14 X 1·83 m or 2·14 X 1·07 m ). The cage size was increased to 0'41 X 0.71 m at four weeks and to 0.41 X 1'07 m at 14 weeks. Changes in th'e numbers of caged birds owing to culling meant that the area per caged

24

BRITISH VETERINARY JOURNAL,

130, 1

bird varied from 0'219 to 0'087 m 2 • Light was provided by 40-W bulbs; the intensity at the floor varied between 6 and 12 lux. There were 12 groups altogether, two cages and two pens for each strain. They were fed chick pellets to seven weeks, growers' pellets from 8-17 weeks and layers' pellets from 18 weeks on. Several birds had to be removed from the cages because feather pecking was severe, probably because the level of illumination had to be high enough to permit accurate observation; these birds took no further part in the experiment. Each group was observed for 10 min twice weekly until they were 24 weeks old; observation times were randomized so that the same group was not always observed at the same time of day. Nine behaviour patterns were selected for recording: Head shake. The head, held normally, was moved from side to side. Movements occurring during feeding or drinking or following an external disturbance were not recorded. Head scratch. The head and bill were scratched with the foot, the leg passing beneath the wing. Body/wing shake. The neck and body feathers were ruffled and the entire body was rotated in an axial plane. Wings were slightly lifted. Wing flap. The flapping action consisted of several wing beats while standing still. Movement flap. Similar to wing flap but forward movement also involved, often running. Wing/leg stretch. One wing was extended backwards and slightly sideways, generally together with the leg on the same side. Ground scratch. With the body bent forward the birds made several backward strokes with one leg, usually followed by the other. Dust bath. Performed with fluffed feathers while in a sitting position. Subsequent activity included bill raking, ground scratching and head rubbing. Preen. The beak was brought into contact with the feathers or skin and one or more different movements were performed: pecking, combing, stroking or nibbling. A fuller description of some of these patterns is given by Kruijt (1964). These movements were selected because, in general, they are of a fairly low priority in a hierarchy of behaviour patterns and do not correlate with any well-defined physiological need, being mostly associated with the maintenance of the plumage or the stretching of muscles. We considered that this kind of behaviour pattern, loosely termed a "comfort movement", would be comparatively sensitive to the environmental constraints produced by close confinement in barren surroundings and might also show changes in incidence in conflict and frustrating situations, becoming disinhibited as a displacement activity when other tendencies were blocked (McFarland, 1965; Wood-Gush, 197 1) . The observation period was split into 15-s sub-divisions; behaviour patterns were recorded in terms of their presence or absence within each of these 15-S periods. The individual birds were identified by means of colour-coded leg rings.

BEHAVIOUR PATTERNS IN FOWLS

Experiment 2 To establish whether cage/pen differences depended on rearing experience, or whether they could be reversed in adult birds, caged birds were transferred to pens and penned birds to cages when they were 30 weeks old. If the day of transfer is designated Day 0, the birds were observed, as in experiment I, for IO min on the afternoon of Day- 1 and for IO min on the morning of Day o. They were then transferred and were observed for 10 min on the afternoon of Day 0 and for IO min on the morning of Day + I. In the following IO days four more periods of observation were carried out. The same birds were used in all three experiments. Experiment 3 In this experiment the activity of caged and penned birds was compared. The same birds as in experiments 1 and 2 were used and observations began when they were 32 weeks old. Groups were observed for 20 min periods divided into sub-units lasting 30-S ; at the end of each sub-unit all activity observed during the preceding 30-S was recorded. Activity was divided into six categories: Resting. The bird did not move during the observation period. Part movement. A part of the body, for example the head or a leg, was moved. Body movement. The entire body was moved; for example, a sitting bird rose to its feet or twisted itself around. Pacing. At least one step forward was taken. Feeding. This implied pecking at and swallowing food particles. Drinking. This is self explanatory. The first four categories of activity are exclusive, only the category involving the greatest degree of movement was noted; for example, if a bird showed both part movement and pacing only pacing was noted. Feeding and drinking however were recorded in addition to the categories of bodily movement. Eleven observations were made of every group; caged birds were then transferred to pens and penned birds to cages and a further six observations were made. The observation periods were randomised to fall at any time between 09.00 hand 17.30 h. RESULTS

Experiment 1 The cumulative incidence of each behaviour pattern at 2, 12, and 24 weeks is shown in Fig. I; the values given are pooled means for all cages and all pens. An analysis of variance was carried out on the cage and pen means and is presented in Table 1. Strain differences were observed in the case of head shake, wing/leg stretch and preen. There were significant differences between cages and pens for all behaviour patterns except body/wing shake and head scratch. Experiment 2 The results are given in Table II as pooled means of each behaviour pattern, before and after transfer. The Wilcoxon test (Siegel, 1956) was used

~

TABLE I

CTl

EXPERIMENT I: ANALYSIS OF VARIANCE OF THE MEAN CUMULATIVE TOTALS OF BEHAVIOUR PATTERNS IN CAGES AND PENS BY 24

Head shake

Body/wing stretch

Wing flap

Head scratch

Wing/leg stretch

Preen

Move flap

--- --------- ---------------------------------------------

Strains Accom, S X A Remainder p

Dust bath

Mean squares

DF

.** =

Ground scratch

WEEKS

9 8 '94** 943'4 1 **. 5'86 4'48

2 I

2 6

<

0'001,

** =

P

<

*

0'01.

1'73 0'09 l'7 6 2,62

= P

19' 01

1'37 4 2 '23 ••• 0 ' 21

55'21 8 ' 07 11 ' 42

0'43

28::\,86 19481 '02*** 225,67 20 7'03

21,84 290 '28*** 59 ' 5° 16'5 1

0 ,80

3 6 '23* 147'28** 35'18* 4,63

5 6 '33** 0'37 2 ' 03

2834'00* 8812 '9 2 ** 93'7 8 5 0 7'88

~

~ .....

U':I <

::t:

0'05,

~ Z

~

TABLE II EXPERIMENT 2:

'-<

o

COMPARISON OF BEHAVIOU R PATTERNS BEFORE AND AFTER PEN/CAGE TRANSFER

c:::

Wilcoxon Cage to Pen Headshake Body/wing shake Wing fl ap Head scratch Preen Ground scratch Dust bath Wing/leg stretch Movement flap

Pen to Cage T

N

5 29 0 14 ° 8

12 12 12 12 12 12 10

14 0

9 8

P

~ ~

8'20 2,06 0 0 ,86 4 0 '23 0 ' 28 1'0 0'11 0

3 ,63 0'92 4,82 1'02 22 '7 2 6'75 1,62 0 '3 1 0 '58

2'48 1'62 1' 16 2'21 29'59 13'1 I 2 ' 47 0,62 1,88

3'7 1 0 ,61 0 1 ' 01 17' 72 0'03 0 0'4 1 0 ' 07

34

<

0 ' 01

NS <

0'01

NS

NS <0'01 <0'05

NS <0'0 1

The values shown are means per bird per 60 min, of observation, pooled by groups and strains, The Wilcoxon matched pairs test was carried out on the 12 separate groups; T is the total, N = the number of matched pairs (ties are disregarded) and P = the two-ta iled probability,

~

~o

BEHAVIOUR PAITERNS IN FOWLS

to determine whether the incidence of the behaviour patterns changed significantly after switching the birds from one environment to the other. A significant change was observed in head shaking, wing flapping, ground scratching, dust bathing and movement flapping; in each case the incidence changed in the direction predicted by the findings of experiment I. Head shaking increased when birds were moved from pens to cages and decreased when they were moved from cages to pens. The other four behaviours decreased when the transfer was from pens to cages and increased when it was from cages to pens. Head shake Head scratch

30

I!:iI Cage

25

~C0ge OPen

6

20

~

20

~

15

g

25

OPen

Body/ wing shake

5

~Cage

OPen

15

4

3

10

2

5

o

2

12

o

24

2

12

24

Preen 280 240

...'0200

Ground scratch ~

100

Cage

Wing flop 6

m Cage

OPen

0

80

~ Cage

5

Pen

.0

OPen

4

60

3 4 2

20 2

12

o

24

2

12

24

o

2

12

24

Dustbothe

Wing / Ieg stretch

14

16

OPen

10

Move flop

f1&jcoge

~Coge

12

8

OPen

6 4 2 2

12

Weeks

24

Cage

OPen

~:

8

E!J

: ~ 2

12 Weeks

24

12 Wee~s

24

Fig. I. The incidence of each behaviour pattern in cages and pens at 2, 12, and 24 weeks. The values shown are pooled cumulative means per bird; the vertical bars represent standard errors. 24 weeks represent 480 min. of observation.

BRITISH VETERINARY JOURNAL, 130,

I

No significant change occurred in body/wing shaking, preening, head scratching or wing/leg stretching. Wing flaps were performed by a number of birds moved from cages to pens in the first 10 min period after transfer; they were abnormal in that the movements of the two wings were poorly synchronized, but this incoordination had disappeared by the following day.

Experiment 3 The findings are given in Table III by strain, as pooled means of each category of activity. The first column, in each case, represents the level of activity before transfer and the second column its level after transfer. Inspection indicated that resting, part movements, feeding and drinking were observed more often in cages, pacing was more frequent in pens and body movements were equally common in both. Analyses of variance were carried out on the pooled means to test the significance of these differences and are summarized in the same table. They confirm that groups of hens, regardless of strain, do indeed spend more time resting, moving parts of their bodies, feeding and drinking when housed in cages but more time pacing when housed in pens. Order effects were significant in the case of resting, part movements, body movements and pacing, showing that the change in incidence when birds were moved from cages to pens was different from that observed when the movement was from pens to cages. Pacing increased considerably when the movement was from cages to pens but decreased only slightly when it was from pens to cages. The opposite was true in the case of resting and of part movements; these activities are dependent variables and an increase in one category must lead to a compensatory decrease in another. DISCUSSION

There was a clear difference, in these behaviour patterns, between birds housed in pens or in cages; interpretation however is difficult. The differences may confidently be ascribed to the different micro-environments, for the birds were housed in the same enclosures, fed the same foods and maintained under the same light regimen. The crucial question is: are the birds responding differentially to particular features of the environment, or does the altered behaviour represent adaptation to an environment which imposes a degree of "stress" ? More contentiously, the question can be phrased: was the behaviour observed in pens "normal" and that in cages "abnormal"? At present "stress" in domestic fowls cannot be assessed objectively in physiological terms, but the relative numbers of birds culled from cages and pens indicate that the former was, under our management, a less satisfactory environment. Several differences are indeed consistent with the notion that the cages and pens provide different stimulus situations. Ground scratching and dustbathing were much more common in pens, which provided a more suitable milieu. The differences in incidence of wing flap and of movement flap, which require adequate space, can readily be accounted for on the basis of physical constraint. Virtually no movement flapping occurred in the caged birds after week 12 (Fig. I).

TABLE III EXPERIMENT 3 : THE EFFECT OF CAGE/PE N TRANSFER ON FEEDING, DRINKING AND ACTIVITY

Strain

Resting

gog

Part movement

Body movement

Pacing

Feeding

Drinking

Cage I 2

3°3 2 °4

0°0 0°1

12 °3 10°8

4° 8 g oo

6 06 5"g

12 °2 11 °5

7°4 g02

15°6 15° 1

g08 12 °0

13°2 5°8

2 °7 log

5° 0 3°5

Pe n

I 2

0°4 0°8

0°0 Oo(

3 °1 6°6

4°7 2°g

9°3 (2°2

goo 8°5

22°2 17 °2

22 °3 24°4

7°6 4° 8

6°0 7°6

2° 1 1°1

1°7 1°7

Cage I 2

2°6 2 °3

0°2 0 °3

13°6 8 0g

3° 8 6 06

7°2 13°5

14°4 13°0

gO( g06

17 °6 II 06

g08 6 01

8°2 9° 2

1°3 2 °3

1°2 5° 2

::r:

Pen

lo( 1°0

0 °4 0°6

4°4 4°5

108 2°0

6 °7 6 01

6 °7 7° 6

22°2 24°4

28 01 2 6 °9

6 °4 8°6

4°8 5°9

1 06 1°0

0°7 1°7

0

Shaver

I 2

Cage I 2

Pen

(

2

3°9 5"2

0°2 0°0

10°3 gog

7°2 4°4

7°9 6°5

(0°0 9°9

11 °5

11 °5

21 °5 20 08

7°0 7°6

gOI 10 °7

2°8 3°2

108 2 °7

0°4 2 °6

1 08 0°0

3°3 3° 1

7°1 log

7° 6 8 °6

9°5 gog

23 °7 22°2

113 00 25"2

7° 6 7°0

4°5 8 01

2°2 2°6

106 2°0

Variance Ratios

Effect Cage Vo Pens Strain Order S X 0 =

I 2 I 2

P < 0°001.

Part movement

7°62 * 0 028 2g06g** 1°02

*.

=

P < 0°01 0

5 1°22*** 0°20 Ig04 1*· 1 °53 • =

Body movement 600 5* II028** 12 °2g·* 0 004

e

:;0

~

>-l tr;j

:;0

'"%j

DF Resting

~......

Z rJ) ...... Z

EXPERIMENT 3: STATISTICAL ANALYSIS OF THE RESULTS

.**

t:t:I

tr;j

8 08

Pacing

Feeding

Drinking

94062*** 4 06g 22 °65** 0°12

14°64** Oog2 0°02 0°5 1

8 °35* 0 06g 0°68 1°8 7

0

:Et""

rJ)

P < 0 °05 0

In the first part of the table "Cage" and "Pen" refer to the location of the group before transfer, as does the first column of mean values beneath each categoryoThe second column below each category gives the mean value after transfer, that is, the group originally in cage I move to pen I, the group in pen I move to cage I and so ono The values represent the number of 30-s petiods in 20 min observation during which the particular behaviour was recorded, expressed as m eans per birds p er observation periodo ~

~

30

BRITISH VETERINARY JOURNAL,

130, I

Other differences are less readily explained. Head shake, wing/leg stretch and preen are more frequent in cages. Wing/leg stretch can be performed in more confined surroundings; it may be a replacement activity for wing flapping. Two explanations might account for the increased preening in the caged birds. First, there was more feather damage in the cages, caused by feather pecking; preening might be stimulated by a need to restore damaged plumage. Second, mild frustration can lead to increased preening which is qualitatively different from normal preening (Duncan & Wood-Gush, 1972); we have not distinguished between the two types. These explanations are not mutually exclusive, as each could make a partial contribution to the increased level of preening; this is supported by' careful examination of our findings. Bareham (1972) reported no increase in preening in his battery birds. As they were housed singly in cages, their plumage will have been in good condition; this would not be a factor in stimulating preening. If the increased preening is partly attributable to frustration, Bareham's (1972) results taken together with ours suggest that the frustration is produced by the social interaction of grouped birds rather than by caging itself. Levy (1944), Bareham (1972) and ourselves have reported more head shaking in caged than in penned birds. We did not record head shakes associated with obvious external disturbances; this may explain why we report a lower incidence than Levy or Bareham. Levy ascribed the increased incidence in caged birds to a neurotic response to frustration of movement; Bareham sees it as a means of increasing sensory input under conditions of social isolation in a barren environment. Our birds were all grouped so social isolation can be ruled out as a contributory factor. The difference is present even in two-weekold chicks, suggesting that the relevant factors begin to operate at an early age. Wood-Gush (1956) tentatively classified it as a displacement reaction to conflict situations; such conflicts may be more frequent when birds are in closer proximity in cages. In experiment 2 all four of the behaviour patterns which showed a higher incidence in pens during experiment 1 also showed a significant change after transfer, whereas of the three behaviour patterns which showed a higher incidence in cages only head shake showed a significant change after transfer. This apparent inconsistency may be explicable in terms of the time scale of the changes. The incidence of the behaviour patterns which are more frequent in pens can be attributed to the influence of the bird's immediate environment; it cannot be ascribed to a long-term developmental effect which has resulted in a permanent inhibition. For example, although wing flapping was virtually absent in the caged birds after 12 weeks, within 10 minutes of transfer into the more spacious environment of the pens it was observed in about 50 per cent of the birds. On the other hand it may be that the behaviour patterns which are more frequent in cages are influenced mainly by long-term factors, except head shaking, which did show an immediate effect. Penned, as opposed to caged, birds spent more time in vigorous activity at the expense of less vigorous activities (experiment 3). Both penned and

BEHAVIOUR PATTERNS IN FOWLS

caged birds spent little time completely immobile, though the proportion was significantly higher for the caged birds. That this inhibition of activity was produced by environmental constraints was shown by comparing the same groups of birds in both systems of housing. Birds which had spent six weeks in cages showed a large increment in activity when placed in pens whereas penned birds moved to cages showed a smaller decrement, as if attempting to maintain their customary activity. In this discussion the concept of frustration has arisen several times. The Brambell Committee (H.M.S.O., 1965) concluded that caging in itself frustrated the "ingrained behaviour" of the fowl. There is little information available either to support or to dismiss this assertion, apart from WoodGush's (1972) demonstration of pre-laying pacing in caged layers. Frustration may however be linked as much to the "stress" inherent in the social organization of closely grouped birds (McBride, 1970) as it is to the method of housing; caution is necessary in attributing the observed changes to one factor or to the other. Behaviour patterns which alter rapidly following a change from cage to pen, or vice versa, may be governed mainly by environmental constraints, whereas the less labile patterns, which do nevertheless show long-term differences, may be influenced more by "social stress". The Brambell Committee (H.M.S.O., 1965) concluded that dust bathing was impossible in cages; this is incorrect, although its incidence is significantly less in cages, it is still appreciable. The Committee too stated that preening was difficult; our findings showed that it was actually more frequent in cages. The results of experiment 3, however, do support the Committee's assertion that walking is restricted in cages. Ground scratching, also, was rarely observed in cages but was common in pens. Wing and movement flapping were negligible in caged birds over 12 weeks old; clearly caging exerts a major influence on these behaviour patterns. The constraint of a behaviour pattern may have harmful effects other than a possible increase in frustration: for example, direct physical changes. Cage-reared broilers have more fragile limb bones, especially humeri, than those reared in pens; these changes, which can result in fractures, are ascribed to restriction of movement and inability to wing flap (Wabeck & Littlefield, 197 2 ) . In conclusion, our findings demonstrate that transfer does lead to a change in incidence of a number of behaviour patterns. The rapidity with which some of these behaviours reappear following a change of environment from cages to pens is especially striking. Our experimental design is such that the precise features of the environment which lead to cage/pen differences cannot be identified with certainty; probably both the amount of space available and the presence of litter are important. VVe should emphasize that, although we have shown that the expression of behaviour patterns is in some way inhibited or constrained (or in the Committee's nomenclature "frustrated") by the nature of the environment, this is not in itself to imply any harmful effect on the animal's wellbeing; such a conclusion would have to be supported by confirmatory physiological evidence.

BRITISH VETERINARY JOURNAL, 130, I ACKNOWLEDGEMENTS

We would like to thank Mr R. Morley Jones for his assistance with certain of the statistical analyses.

REFERENCES

BAREHAM, j. R. (1972) . Br. vet. J. 128, 153. DUNCAN, I.j. H. & WOOD-GUSH, D. G . M . (1972). Anim. Behav. 20,68. EWBANK, R. (1969). Outlook on Agriculture, 6, 41. H.M.S.O. (1965). Report of the Technical Committee to Enquire into the Welfare of Animals kept under Intensive Livestock Husbandry Systems. Cmnd 2836. London: Her Majesty's Stationery Office. KRUI]T,j. P. (1964). Behaviour, Suppl. XII. LEVY, D. M. (1944), Am. J. Orthopsychiat. 14,644. McBRIDE, G. (1970) . In Aspects of Poultry Behaviour, ed. Freeman, B. M. & Gordon, R. F. B.E.M.B. Symp. 6, 3. Edinburgh: Br. Poult. Sci. McFARLAND, D. j. (1965). Anim. Behav. 13,293. SIEGEL, S. (1956). Nonparametric Statistics for the Behavioral Sciences. New York: McGraw-Hill. WABECK, C. j. & LITTLEFIELD, L. H. (1972). Poult Sci. 51, 897. WOOD-GUSH, D. G. M. (1956). Br. J. Anim. Behav. 4, 133. WOOD-GUSH, D. G. M. (1971). The Behaviour of the Domestic Fowl. London: Heinemann. WOOD-GUSH. D. G. M. (1972). Anim. Behav. 20, 72.

(Accepted for publication 13 March 1973)

Genres de cODlporteDlent face au confort et d'activite chez les oiseaux dODlestiques: Une cODlparaison entre cages et poulaillers (Black et Hughes) ResUDle. La frequence de neuf genres de comportement chez trois especes d'oiseaux gardes dans des cages ou des poulaillers a ete comparee. Il y eut peu de differences entre especes, mais Ie battement d'ailes, battement de mouvement, bain de poussiere et coups d'ongles au sol, etaient plus frequents dans les poulaillers que dans les cages, alors que Ie hochement de t~te, nettoyage des plumes avec Ie bee, et l'allongement des ailes et des jambes, ctaient plus frequents dans les cages. Le transfert de groupes d'oiseaux entre cages et poulaillers resultat dans des changements importants a la frequence des 5 premiers comportements mentionnes ci-dessusj les changements se produisirent dans la direction predite. Les oiseaux d es cages etaient en general moins actifs que ceux des poulaillers, mais passaient plus de temps a manger et a boire.

Typen von Wohlbefinden und Aktivitat bei Hiihnern: Vergleich zwischen Hiihnern, die in Kilfigen, und solchen, die in Stallen untergebracht waren (Black und Hughes) Zusanunenfassung. Das Vorkommen von neun Arten des Verhaltens von drei Hiihnerrassen wurde verglichen bei Unterbringung in Kafigen oder in Stallen. Man fand nur geringe Unterschiede, die fUr die Hiihnerrassen charakteristisch waren, aber Fliigelschlagen, Taumeln, Baden im Staub und Scharren am Boden wurden haufiger in Stallen beobachtet, wahrend in Kafigen haufiger Kopsfchiitteln, Putzen und Strecken der Fliigel und Beine gesehen wurde. Wenn die in Kafigen und Stallen gehaltenen Hiihner miteinander ausgetauscht wurden ergaben sich charakteristische Wechsel im Auftreten der ersten fUnf der oben beschriebenen Verhaltensweisen. Die Anderungen entprachen der Voraussage. Die in Kafigen gehaltenen Hiihner waren in der Regel weniger aktiv als die in den Stallen und brachten ihre Zeit mehr mit Fressen und Trinken zu.

BEHAVIOUR PATTERNS IN FOWLS

33

Patrones de cotnportalDiento para con la cotnodidad y actividad de las aves dotnesticas: Una cotnparacion entre jaulas y corrales (Black y Hughes) Resutnen. Se compar6 la incidencia de nueve patrones de comportamiento en tres dases de aves en jaulas 0 en corrales. Hubieron pocas diferencias entre las dases, pero los aleteos, aleteos con movimiento, banos de polvo y aranado del suelo fueron mas frecuentes en los corrales que en las jaulas. La transferencia de aves de jaulas a corrales y viceversa result6 en cambios significativos en la incidencia de los cinco primeros comportamientos de mas arriba; los cambios ocurrieron segUn se habia anticipado. Las aves en las jaulas fueron por 10 general menos activas que las que ocuparon los corrales, pero pasaron mas tiempo alimentandose y bebiendo.