Differential use of space by eight species of birds in a free-flight zoological park aviary

Applied Animal Ethology, 3(1977) 105-126 o Elsevier Scientific Publishing Company, Amsterdam

DIFFERENTIAL FREE-FLIGHT

105 - Printed

in The Netherlands

USE OF SPACE BY EIGHT SPECIES OF BIRDS IN A ZOOLOGICAL PARK AVIARY

BETH E. LEUCK Department of Zoology, University of Oklahoma, Norman, Okla. (U.S.A.) The Oklahoma City Zoo, Oklahoma City, Okla. (U.S.A.) (Received

30 March,

and

1976)

ABSTRACT Leuck, B.E., 1977. Differential use of space by eight species logical park aviary. Appl. Anim. Ethol., 3: 105-126.

of birds in a free-flight

zoo-

Eight species of birds (jabiru stork, Jabiru mycteria; maguari stork, Euxenura galeata; king vulture, Sarcoramphus papa; turkey vulture, Cathartes aura; black vulture, Coragyps atrata; Orinoco goose, Neochen jubata; fulvous whistling duck, Dendrocygna bicolor; black-bellied whistling duck, D. autumnalis) were studied in a large zoo aviary to determine their use of topographical regions (areas), substrates and heights during a 3-month period. Positions of individuals in the aviary were recorded and species were compared to others of the same taxonomic family to determine if they exhibited differential use of space. Resting and self-care were the most frequently recorded behavior patterns. Certain areas, substrates and heights were utilized by each species regardless of behavior. Each species restricted most of its activity to two or three contiguous areas within the aviary. Space use was correlated with the location of food, presence of shade or similarity to substrates utilized in the wild. Only the vultures made appreciable use of heights over 1.5 m above ground level. Conspecifics were found with each other more often than with heterospecifics of the same family. The waterfowl and maguari storks tended to flock. Maguari storks, king vultures, Orinoco geese and fulvous whistling ducks were restricted in their use of space while the other species ranged throughout the aviary. Environmental structure strongly influenced space utilization, and there were indications that intra- and interspecific interactions may have also affected use of space.

INTRODUCTION

Distribution in space is a fundamental attribute of animals (King, 1970), but species differ in the types of environments they select and the manner in which they use available space (Mason, 1968). The space which an animal utilizes, called its living space by Hediger (1964), is not homogeneous in structure but permits the animal to select particular sites where daily and seasonal activities may occur. Therefore, animal activities, or behavior, are site-specific as well as situation-specific (King, 1970). Two categories of spatial factors affect an animal’s site choice. Inanimate factors are topographical and vegetational variations in the habitat. Animals

106

respond to these inanimate factors as objects that provide structure in the environment and orient nonrandomly toward them. The animate spatial factors in an organism’s environment include other animals with which the living space is shared (Wilson, 1972). Social force fields existing among animals may be repulsive where inter-individual distances are maintained mainly by agonistic behavior (McBride, 1964, 1971 b; Kummer, 1971), or they may be attractive resulting in the formation of affiliated groups of animals. Animals have spacing relationships to both conspecifics and heterospecifics (McBride, 1971 b). The repulsive and attractive forces of both other animals (animate factors) and environmental structure (inanimate factors) produce a spacing pattern unique to a group of animals in a particular environment. Spacing in animal communities also varies seasonally and diurnally (McBride, 1971 a). Watson and Moss (1971) reported seasonal changes in the spacing patterns among red grouse (Lagopus lagopus) in Scotland. WoodGush (1959) demonstrated a diurnal rhythm of spacing patterns within a group of domestic chickens. Since species within a community differ in behavior, a study of the correlation of behavior, site, proximity to other animals and diurnal and seasonal changes may be significant in determining some of the environmental features to which particular animals respond. For some animals the structural features within the habitat may govern their space utilization (Brown and Orians, 1970); for others the presence of other individuals may strongly affect their use of available space. The purpose of this study was to investigate some of the environmental and social factors which determine the spacing pattern of eight species in a captive bird community. It was assumed that animals do not wander randomly but utilize specific sites in their living space for particular purposes (Hediger, 1964). The sites may vary from species to species, based on differential perceptual selectivity of environmental elements (King, 1970). By observing several groups of related species confined in the same environment, the nonrandom use of available space through time can be determined. Since birds fly, a three-dimensional representation of space use is necessary. Few reports are available in the literature describing the three-dimensional use of space in response to both animate and inanimate environmental factors. In this paper behavioral responses to space, species-specific utilization of space and monthly and diurnal changes in space use were studied. In addition the species-specific patterns by species in this community were determined to assess animate and inanimate features affecting space utilization. METHODS The birds were observed in a large (approximately 0.24-ha) outdoor aviary, the “Condor Cliffs and Patagonian Panorama”, at the Oklahoma City Zoo, Oklahoma City, Oklahoma. The aviary varied from 8.5 to 21.0 m high and contained gunite cliffs up to 5.0 m high, pools, waterfalls, shrubs, gravel, dirt,

107

grass, logs, trees, caves and nesting holes. The aviary design facilitated my doing a space utilization study because it was complex enough to present the birds a choice of habitat, but its wire perimeters usually kept the study animals in sight from an observation point and prevented predation from outside sources. Subjects Approximately 30 species of birds, all with ranges that include South America, were in the aviary at the time the study began. The following species were observed: jabiru stork (Jubiru mycteriu), maguari stork (Euxenura guleatu), king vulture (Surcorumphus pupa), turkey vulture (Cuthurtes aura), black vulture (Corugyps utrutu), Orinoco goose (Neochen jubutu), fulvous whistling duck (Dendrocygnu bicolor), and black-bellied whistling duck (D. autumnalis). There were at least two birds of each species which reduced personality effects. The eight species could be grouped into three taxonomic families for comparisons among and within closely related groups. The species representing the three families have sympatric ranges in South America. Two adult jabiru storks of unknown sex and three adult maguari storks of unknown sex represented the family Ciconiidae (storks). The jabiru stork is a resident of South America, although it ranges as far north as southern Texas (Bent, 1963; Kahl, 1971). The species forages in wet meadows and shallow water and constructs an arboreal nest (Bent, 1963; Kahl, 1971,1972). The maguari stork is also a resident of continental South America. It forages in wet meadows but nests on the ground in marshy areas (Kahl, 1971). Cathartidae (New World vultures) were represented by one juvenile and six adult king vultures of unknown sex, one juvenile and two adult turkey vultures of unknown sex and one adult and two juvenile black vultures of unknown sex. The king vulture ranges from central Mexico to northern Argentina (Brown and Amadon, 1968) and inhabits deep tropical forests and the ranch lands of the dry tropical forest (Grossman and Hamlet, 1964; Slud, 1964). It flies in flocks and nests in the tops of trees, large holes in dead trees and rock crannies in low forested cliffs (Gilliard, 1958; Olivares, 1965). It spends much of its time perched in the forest or flying slightly above the forest canopy (Brown and Amadon, 1968). Turkey vultures range from southern Canada to South America (Brown and Amadon, 1968) and are found in forests and groves of trees, along roads and on man-made structures such as flagpoles and telegraph poles (Verrill, 1923; Olson et al., 1967). They often roost on perches in high branches of dead trees (Coles, 1944). Black vultures range from the eastern United States to central Patagonia (Brown and Amadon, 1968) inhabiting wooded and open areas and urban areas (Verrill, 1923, Bent, 1961). They spend much of their non-flying time on the ground and will congregate in urban garbage dumps by the hundreds (Verrill, 1923; McIlhenney, 1939). Anatidae (ducks, geese and swans) were represented by seven adult Orinoco

108

geese of unknown sex, five adult (two male, three female) fulvous whistling ducks and seven adult (three male, four female) black-bellied whistling ducks. The Orinoco goose ranges east of the Andes from Venezuela to northern Argentina (Delacour, 1954) and inhabits tropical forests, the banks of Savannah rivers or wooded river banks (Phillips, 1922; De Schauensee, 1964). The species is primarily a grazer, nests in hollow trees and perches readily (G. Cherrie in Phillips, 1922; Delacour and Mayr, 1945; Delacour, 1954; Johnsgard, 1965). Fulvous whistling ducks range from the southern and western United States to western Mexico, from Panama and Columbia to the Guianas, from eastern Brazil to northern Argentina and throughout much of East and South Africa. They are also residents of Madagascar, India, Burma and Ceylon (Delacour, 1954). They inhabit open areas near water containing reed beds, grass-covered spits of land, thickets and rice fields (E. Baker in Phillips, 1922; T. von Heuglin in Phillips, 1922; Delacour, 1954; Meanley and Meanley, 1959). The blackbellied whistling duck ranges from southern Texas to northern Argentina (Delacour, 1954) and is found in shallow water and on the banks of bodies of water bordered by woods (Phillips, 1922; Bolen, 1964), although Bolen (1967) has found many flocks around ponds in Savannah pastures. It is a grazer and a shallow water dabbler, perches readily and nests in cavities of trees or occasionally on the ground (Bolen, 1964; Rylander and Bolen, 1970). One jabiru stork, one king vulture, two Orinoco geese and several fulvous and black-bellied whistling ducks were pinioned. No behavioral differences between these birds and unpinioned birds of the same species were noted except for the inability of the king vulture to fly upward. Observation

procedures

Data were recorded on behavioral checklists at the time observations were made. For each observation the species of bird, its behavior, the area in the exhibit, the substrate where located and the height above ground were recorded. Behavior categories were based on observations done prior to the study. Ten general behavior categories were used; feeding and drinking, resting, selfcare, locomotion, copulation, attack, mutual preening, display - increase distance, display - decrease distance, and display - neutral. Display - increase distance was recorded when an activity not defined by another behavior category occurred and a conspecific or heterospecific moved away after the behavior began. Display - decrease distance was recorded when the distance between two or more birds decreased while the behavior occurred. Display neutral was recorded if a display behavior was not applicable to other cate: gories and no change in distance among birds was observed. Two behavior categories, copulation and attack, were never recorded. The aviary was divided into 13 areas (Fig.1) based on the topography of the exhibit. The areas varied from 17.6 mz to 73.6 m2 in size. Ten substrates were available in the aviary: trees, bushes, shrubs (Yucca sp.), rocks (gunite), logs,

109

Fig.1. Division of the aviary into 13 areas based on topography. The available substrates are listed for each area. T = tree, Sb = shrub, B = bush, Rk = rock, L = log, G = ground, W = water, Rg = railing, Sn = sign.

ground (including wooden walkways) and gravel, water, railings and roof rim, and signs and posts; air was also recorded as a substrate. Height of the bird under observation was recorded in one of four categories: O-l.5 m, 1.6-3.0 m, 3.1-4.5 m and above 4.5 m. The lowest portion of each area constituted 0 m (base height). Areas 2, 6, 7, 8 and 12 had low, Areas 1, 4, 5 and 9 middle, and Areas 3, 10, 11 and 13 the highest base heights. Small circles of paint were placed on tree trunks and gunite to demarcate the height categories. Area, substrate and height comprised the general category of site. The eight species were observed chronologically in random order. An individual of the species to be observed was chosen randomly and watched for 10 min (focal animal sampling, Altmann, 1974). At the beginning of the lo-min sampling period and at l-min intervals the behavior state, area, substrate and height of the individual were noted. This process was repeated until all eight species were observed. Behavioral state was recorded instantaneously, so those behaviors of short duration, such as social displays, were less likely to be recorded than states with long durations, such as resting. To determine diurnal changes in behavior, days were divided into three periods: (1) 07.00-11.00, (2) 11.00-15.00 and (3) 15.00-- 19.00 h Central Standard Time. Equal numbers of records for each species were taken for each period of the day and for each of three months, June, July and August,

110

1974, resulting in 1 080 discrete observations for each species. At seven evenly spaced intervals on eighteen 12-h days the positions of each member of the eight species were recorded on a two-dimensional map of the aviary, resulting in 126 maps for the complete study. Analysis The checklist data were placed in matrices showing the frequency of behavior, area, substrate and height use by each species and designed specifically for analysis of variance using the methods of Sokal and Rohlf (1969). Because the data were expressed as proportions of the total 1 080 observations, the arcsine transformation was used (Sokal and Rohlf, 1969). The four-way analyses of variance performed included (1) species X behavior X period X month, (2) species X area X period X month, (3) species X behavior X area X period and (4) behavior X area X substrate X height for each species. The maps marked with individuals’ positions were compiled into eight final maps, one for each species. The final maps were drawn by placing a grid system of 292 square grid sections over the daily record maps of the aviary (each grid section = 1.5 m*) and determining the percentage of the total map observations of each species occurring in each grid section. The final maps were then compared among species within a family to ascertain any differential use of areas throughout the study period. Spacing of species at the same point in time (temporal separation) was determined from the daily record maps by noting on which maps conspecifics were present in the same grid section as well as in which grid sections members of two or three species within a family were located. To compare association with conspecific versus heterospecific ratios (association numbers) were derived. The conspecific association number was A/B, where A is the total number of grid sections in which two or more conspecifics occur and B is the absolute integer value of the total number of grid sections occupied by the species divided by two. Heterospecific association numbers were derived from C/D, where C is the total number of grid sections in which two or more heterospecifics occur and D is the total number of grid sections occupied by the species with the lowest grid section occurrence. The denominators express the theoretical maximum number of grid sections containing two or more conspecifics or heterospecifics for each pair of species. The denominator values ranged from 5 to 29 for the conspecific and 10 to 32 for the heterospecific ratio. Larger association numbers mean the animals occurred together more often. A one-way (two level) analysis of variance using the conspecific association number of each period in each month vs the heterospecific association number was performed to discover if each species was associated more often with conspecifics than heterospecifics. RESULTS

The results of all analyses of variance are reported

in Tables I and II. Percent

I

*P < 0.05.

S (7) B (7) P (2) M (2) S x B (49) s x P(14) S x M (14) B x P (14) B x M (14) P x M (4) S x B x P (98) S x B x M (98) S x P x M (28) B x P x M (28)

SxBxPxM 0.10 93.26* 0.02 0.01 2.03* 0.11 0.18 0.14 0.22* 0.03 1.09 0.74 0.18 0.13 S (7) A (12) P (2) M (2) S x A (84) s x P(14) S x M (14) A x P (24) A x M (24) P x M (4) Sx Ax P(168) S x Ax M (168) S x P x M (28) A x P x M (48)

SxAxPxM 1.96* 12.04* 0.06 0.16* 34.30* 0.37 0.39 1.15* 3.77* 0.07 7.68* 29.06* 0.32 1.43* S (7) B (7) A (12) P (2) S x B (49) S x A(84) s x P (14) B x A (84) B x P (14) A x P (24) S x B x A (588) S x B x P (98) S x A x ? (i68) Bx Ax P(168)

SxBxAxP 0.65* 26.12* 4.88* 0.01 2.24* 17.96* 0.15 7.48* 0.03 0.63* 29.15* 0.51 2.35* 1.29

Four-way analyses of variance involving species (S), behavior (B), area (A), period (P) and month (M). Values shown are the sums of squares of each main effect or interaction expressed as a percentage of the total sums of squares of the analysis. Degrees of freedom are in parentheses

TABLE

A S S H H H Ax S Ax H Sx H Sx H

*P < 0.05.

H Bx Bx Ax Bx Ax Sx Bx Bx Bx Ax

B

BxAxSxH __~ .~~___

~~_

2.50* (3) 1.80* (1;) 11.36* (6) 6.53* (1) 1.08 (33) 2.81* (18) 18.73* (66) 1.95* (3) 2.86* (11) 10.61* (6) 10.15* (198) 1.15 (33) 2.66* (18) 15.84* (66)

J

_

(12) (6) (8)

2.93 (3) 1.40f (k) 2.62* (5) 1.87* (3) 1.15 (i2j 1.47 (15) 17.69* (20) 0.59 (9) 4.15* (12) 8.02* (15) 12.91* (60) 2.99* (36) 4.73 (45) 22.20* (60)

9.24* (3) 57.86* (4) 0.11 (2) _

12.03* 3.40* 11.40* _

K

M 3.62* (3) 3.42* il;) 0.60* (4) 6.98* (3) 2.37* (36) 1.02* (12) 15.45* (48) 2.75* (9) 3.41* (36) 5.91* (12) 14.46* (144) 3.75 (108) 3.69* (36) 18.41* (144)

T

4.22* (3) 1.22 (33) 1.88* (18) 12.80* (66) 1.86* (9) 3.26* (33) 8.19* (18) 10.28* (198) 3.38 (99) 4.48* (54) 22.38* (198)

#)

3.62*(3) ;:;;:

B

16.05* (15) 6.51* (6) 4.90 (10) -

19.71 (9) 12.81* (6) 5.93 (6) _ _ _

18.20*(3) 35.59* (5) 10.34* (2) -

F

13.08*(3) 34.29* (3) 13.97* (2) _

0

Behavior (B) x area (A) x substrate (S) x height (H) analysis of variance for each species. Values shown are the sums of squares of each main effect or interaction expressed as a percentage of the total sums of squares of the analysis. Degrees of freedom are in parentheses. J = jabiru stork. M = maguari stork, K = king vulture, T = turkey vulture, B = black vulture, 0 = Orinoco goose, F = fulvous whistling duck, BB = blackbellied whistling duck

TABLE II

_

5.71* 14.36* 15.06* _ _ _ _

12.87* 8.64* 28.66* -

BB

(21) (15) (35)

(3) (7) (5)

113

occurrence of behavior categories for all species and use of areas, substrates and heights in the exhibit are given in Tables III, IV, V and VI. Activities of all species varied during the study, ranging from 66.9% of the total observations for resting to almost 0% for display - decrease distance (Table III). In addition, behavior accounted for most of the variance in the species X behavior X period X month analysis of variance (Table I). Area use also varied among the species and differed from the expected use based on area size (Tables I and IV). The variance attributed to the behavior X area interaction shows each species utilized certain areas for particular behavior patterns (Table I) but did not perform activities in the same areas in equal proportions as indicated by the contribution of the species X behavior X area variance. For example, jabiru storks rested most frequently in Area 2 but all display neutrals occurred in Area 10, while black-bellied whistling ducks used Area 12 most often for resting and locomotion was recorded most in Area 8. Utilization of areas and environmental elements was species-specific. Each species used certain areas more frequently than others and, within each area, was found most often on certain substrates and at certain heights (Tables II, III, IV, V and VI). Jabiru storks were found most often below 1.5 m but were occasionally seen at 1.6-3.0 m (Table VI). They used all areas except Area 7 and were most frequently found resting or engaging in self-care on the ground or rocks in Area 2, 4, 11 or 13 (Tables III, IV, V). The rocks, ground and water in Area 2 were the primary substrates used by maguari storks (Tables IV and V), which were most frequently observed resting, feeding or engaging in self-care at heights not over 1.5 m (Tables III and VI). All heights were utilized by king vultures but they were found below 3 m twice as often as above (Table VI). They were most frequently found resting on trees and rocks in Areas 4 and 10 (Tables III, IV, V). Turkey vultures were found in all areas at some time during the study but Area 9 received the heaviest use (Table IV). The vultures utilized all substrates but bushes. Trees were used one-third more frequently than any other single substrate (Table V). However, they were found twice as frequently below 3 m as above, usually resting (Tables III and VI). The rocks in Area 10 were utilized slightly more frequently than any other substrate by the black vultures (Tables IV and V). They utilized sites below 1.5 m as frequently as sites above (Table VI). Orinoco geese were completely terrestrial, never being found above 1.5 m (Table VI). They frequented Area 2 five times as often as other areas (Table IV). Ground was the preferred substrate, although rocks and water were also utilized, usually for resting (Tables III and V). Area 8 was used more than other areas, usually for resting, by fulvous whistling ducks (Tables III and IV). They utilized only heights below 1.5 m (Table VI) and were found on the ground as frequently as in water and on rocks (Table V).

~~ ~--

0

Mutual preening 0 0 0.3

Increase distance

Decrease distance

Neutral

Display -

8.2

17.7

Locomotion

Self-care

9.5 64.4

J

Resting

Feeding and drinking

Behavior

__

_

_

0

0

0

0.2

6.5

21.6

2.7

0

0.2 0

0 0

0.1

0

7.7

0.2

24.3

3.6

65.1

T

22.3

2.6 71.0

13.6

K

58.1

M

0 0

0

0.4

0.2

0

0.1

0.2

9.7

10.0

15.3 5.5

69.0

10.7

0

74.1

4.9

B 5.7

0

0

0.8

0

13.1

17.5

62.8

F

0.2

0

0.2

0

7.7

16.4

70.4

5.2

BB

0.1

0

0.2

0.1

7.8

18.1

66.9

6.9

Mean

Percent occurrence of behavior categories (of 1 080 observations) of eight species of birds over the 3-month study period. J = jabiru stork, M = maguari stork, K = king vulture, T = turkey vulture, B = black vulture, 0 = Orinoco goose, F = fulvous whistling duck, BB = black-bellied whistling duck

TABLE III

IV

0

4.8

7.6

6.5

13.0

2.6

14.4

7

8

9

10

11

12

13

x2 for observed

2.9

0.3

5

6

9.7

18.1

3

4

3.2

17.1

2

J

1

Area

0.9

4.8

2.4

8.8

36.3

3.2

8.1

1.9

2.3

6.2

3.2

8.0

13.8

T

means = 49.87***.

0.1

0

vs expected

0

0

38.3

0.2

0

0

0

0.7

35.6

18.1

0

6.9

K

4.9

0

0

0.4

4.1

0

2.3

0

0

1.8

86.6

0

M

8.4

2.0

3.1

1.7

27.7

14.2

1.9

12.0

3.3

0

7.1

5.3

13.1

B

0

0

1.8

0

0

0

5.6

0.4

15.4

0

0

0

76.9

0

0

0

9.0

6.8

0

0

4.4

0

19.4

0

0

2.9

57.6

F

0

30.8

2.3

0

11.8

24.7

0

7.1

6.4

7.3

0.2

8.6

0.7

BB

7.5

2.6

2.2

8.4

2.4

10.2

9.2

12.7

6.3

5.0

2.7

5.8

9.4

7.0

8.4

8.5

2.4 4.9

8.5

8.8

11.2

10.9

Expected mean

9.3

4.8

26.8

4.1

Observed mean

Percent use of areas (of 1 080 observations) of eight species of birds over the 3-month study period. Expected means based on area size. J = jabiru stork, M = maguari stork, K = king vulture, T = turkey vulture, B = black vulture, 0 = Orinoco goose, F = fulvous whistling duck, BB = black-bellied whistling duck

TABLE

0.3 33.9 19.3 0 0 0

13.0 50.0 4.3 0.4 0 0.2

Water

Railing

Sign

Air

Rock

Log

0 46.6

0 28.9

Shrub

Ground

0 0

3.2 0

M

Bushes

J

Tree

Substrate

0.4

2.8

4.1

0.1

8.2

0.2

45.2

0

7.7

31.4

K

0.7

0.3

21.9

0.3

16.0

5.8

17.1

0.8

0

36.9

T

0.2

2.5

17.2

0.6

25.2

3.7

33.1

1.5

0

16.0

B 0

0

0

0

0

0.1

14.4

0

0

0

21.8

0.2 52.0

0.3

26.0

0

0

0

F

69.1

16.1

0

0

0

1.9

13.0

60.3

4.4

19.1

0.5

0.9

0

BB

0.2

0.7

5.7

9.2

39.3

3.5

29.0

0.4

1.1

10.9

Mean

Percent use of substrates (of 1 080 observations) of eight species of birds over the 3-month study period. J = jabiru stork, M = maguari stork, K = king vulture, T = turkey vulture, B = black vulture, 0 = Orinoco goose, F = fulvous whistling duck, BB = black-bellied whistling duck

TABLE V

z m

117

TABLE VI Percent use of heights (of 1 080 observations) of eight species of birds over the 3-month study period. J = jabiru stork, M = maguari stork, K = king vulture, T = turkey vulture, B = black vulture, 0 = Orinoco goose, F = fulvous whistling duck, BB = black-bellied whistling duck Height (m)

J

M

K

T

B

0

w1.5

93.5

100.0

31.4

55.6

53.9

100.0

F

BB

100.0

100.0

Mean 79.3

1.6-3.0

6.5

0

38.1

11.5

27.4

0

0

0

3.1-4.5

0

0

14.3

19.9

13.1

0

0

0

5.9

Above 4.5

0

0

16.2

13.1

5.6

0

0

0

4.4

10.4

Black-bellied whistling ducks were never found above 1.5 m and used all areas but 7, 10 and 13 (Tables IV and VI). They were most often found resting or engaging in self-care on the ground but water and rocks were also utilized (Tables III and V). Table II indicates the interaction between areas, substrates and heights for each species. The use of particular sites by a species may not have been due to behavioral choice but to the unequal distribution of substrates over all areas and heights and to limited substrate choice at greater heights. Both behavior and area use showed a slightly greater variation over the 3 months of the study than during the three periods of the day (Table I). Month. ly variations for both factors may be related to temperature fluctuations over months. For example, since resting was the most frequently observed behavior category, resting frequency of all species and the mean high temperature of each month, obtained from the nearest United States Weather Bureau station, were compared. In June (mean high temperature of 30.2”C) 1 855 observations, in July (mean high temperature 35.8”C) 1 995 observations, and in August (mean high temperature 32.3”C) 1 836 observations of resting birds were made, indicating that the birds rested more in hot weather. Area use also varied monthly but the variance attributed to the area X month interaction is small (Table I). However, this variation again can be compared with temperature fluctuations. For example, the Orinoco geese were recorded in Area 6, a region with no shade or water, for 6.9%, 1.9% and 6.6% of the observations for June, July and August respectively. The reduced utilization of Area 6 during July indicated the Orinoco geese shifted their area use in hot weather. Spacing patterns are indicated in Figs. 2, 3 and 4. The degree of association with conspecifics and heterospecifics is in Table VII and can be visualized from the figures. Jabiru storks utilized all parts of the aviary except Area 7 while the maguari storks were restricted to a small region comprised of Areas 2, 6 and 8 (Fig.2). Maguari storks associated more with each other than with the jabirus while the jabiru storks were attracted to neither the maguari storks nor each other (Table VII).

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TABLE

VII

Comparison of occurrence in the same grid section with conspecifics and heterospecifics within the same family. * indicates a significant association number difference (see text) between conspecifics and heterospecifics at P < 0.05. J = jabiru stork, M = maguari stork, K = king vulture, T = turkey vulture, B = black vulture, 0 = Orinoco goose, F = fulvous whistling duck, BB = black-bellied whistling duck Conspecific

Conspecific association number

J-J M-M

0 0.23

K-K K-K T-T T-T B-B B-B

0.35 0.35 0.15 0.15 0.21 0.21

* * *

o-o

0.53 0.53 0.69 0.69 0.50 0.50

* * * * * *

o-o F-F F-F BB-BB BB-BB

*

*

Heterospecific association number

Heterospecific

0 0.04

J-M M-J

0.01 0.05 0.01 0.08 0.05 0.08

K-T K-B T-K T-B B-K B-T

0 0.01 0 0.11 0.01 0.11

O-F 0-BB F-O F-BB BB-0 BB-F

0 JABIRU

STORKS

e MAGUARI

Cc

a I.Jm

0

I-S%

0

6-IO%

0

II-

0

16-20%

STORKS

IS%

Fig.2. Positions of the jabiru storks and maguari storks in the aviary over a period of 3 months. Size of geometric figure indicates the percent of occurrence in a 1.5 m2 grid section.

119

.

KING

VULTURE

0 TURKEY

*BLACK H

VULTURE VULTURE

0

I-S%

0

6-10X

0

II-lb%

= l.Sm

Fig.3. Positions of the king vultures, turkey vultures and black vultures in the aviary over a period of 3 months. Size of geometric figure indicates the percent of occurrence in a 1.5 mz grid section.

.

ORINOCO

m ‘ULVOUS

GEESE WHISTLING

0 DUCKS

0

l-S% 6-10%

Fig.4. Positions of the Orinoco geese, fulvous whistling ducks and black-bellied whistling ducks in the aviary over a period of 3 months. Size of geometric figure indicates the percent of occurrence in a 1.5 m* grid section.

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King vultures were more restricted in their use of space than the more mobile turkey and black vultures (Fig.3). The king vultures were associated more often with conspecifics than with related heterospecifics. Turkey and black vultures were more often found with conspecifics than king vultures, but no differential association was evident when the turkey and black vultures were compared with each other (Table VII). Orinoco geese and fulvous whistling ducks limited their utilization of the aviary to only a few areas. The amount of use of each area by each species differed. Black-bellied whistling ducks were found in more areas of the aviary than the other anatids (Fig.4). All anatid species were associated more often with conspecifics than with related heterospecifics. The whistling ducks were observed in interspecific “threat bouts” seven times during the study. The ducks faced each other from as close as a meter and threatened the other animal with vocalizations and the head-low-and-forward posture (Johnsgard, 1961). Black-bellied whistling ducks eventually displaced the fulvous whistling ducks in all instances observed. DISCUSSION Brereton (1971) and Wood-Gush (1959) found diurnal changes in behavior frequencies in eastern rosellas (Plutycercus eximius) and domestic chickens. Wood-Gush (1959) found no difference in the behavior of chickens between two months (December and June), although the chickens were housed in outdoor pens. In my study, behavior frequency varied slightly from month to month but not among periods of the day. Area use varied with time of day and month. The variances for behavior X month, area X month and area X period were small, possibly indicating time factors were unimportant compared to environmental factors. This lack of daily and monthly variations in behavior frequencies and area use is puzzling in light of common knowledge of diurnal and monthly or seasonal rhythms in captive and wild birds. If my observations had included the twilight periods, diurnal differences might have been detected. Site-specificity of animal activities has been noted in the wild and captivity (Hediger, 1964) and attributed to the perceptual selectivity of the animal (King, 1970). The distribution of food in the environment seems to be the most important single factor determining a wild bird’s site selection (Brown and Orians, 1970) and much of a wild animal’s time is devoted to procuring food (Hediger, 1964). In this study, a response to food would be shown if each species more often utilized areas where appropriate food was located. For example, Area 2 was heavily used by the maguari storks and Orinoco geese, possibly because of the foods available. Both species consumed smelt placed in the water and the geese fed on grains and vegetables in food pans. The jabiru storks ate the smelt in Area 2 and foraged in the bermuda grass (Cynodon dactylon) in Areas 4 and 13. Food pans for carnivorous birds were in heas 3, 9 and 10. The king and black vultures utilized Area 10 most frequent-

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ly and turkey vultures utilized Area 9 most often. The frequent use of Area 4 by king vultures may relate to its contiguity to the food pan in Area 3, since most observations of king vultures in Area 4 located them in a tree near the food pan. A food pan for whistling ducks was in Area 6, but the ducks utilized Area 8 adjacent to 6, and Area 12. If percent use of the three most heavily utilized areas for each species is examined, 55.0-97.9X of all occurrences were recorded in the three areas. In all cases, two of the most heavily utilized areas are contiguous; for the king vultures and waterfowl all three areas are contiguous. By utilizing one region of the aviary for all activities the birds minimized energy expended going from one site to another. There appear to be similarities between species’ site choice in the aviary and the utilization of habitat features in the wild. In some cases displays were and in others were not similar to those seen in wild animals. Jabiru storks utilized a log in Area 2 for both resting and self-care. Other species were never observed on the log. Feeding occurred on the ground and occasionally in water in Areas 2, 4 or 13. Kahl (1973) describes all feeding activities of jabiru storks in the wild to be in shallow water probing vertically downward. In the aviary the storks foraged in bermuda grass. The lack of marshy regions in the aviary may have forced the storks to shift their foraging sites to grass. The jabiru storks’ display behavior consisted of three occurrences of display - neutral in Area 10 on a gunite surface. This display (dash forward about 10 m and dash back to original position) appeared analogous to the wing-flapping performances of wild jabiru storks (Kahl, 1971) but it occurred on a hard surface rather than in water. It was not directed at another jabiru as described by Kahl. Regardless of activity, a low rock ledge in Area 2 as well as a pool in Areas 8 and 12 were utilized by maguari storks for feeding and resting. No area in the exhibit resembled grassy marshes which maguari storks naturally inhabit (Kahl, 1971). The storks in the aviary may have been attracted by food in Area 2 and by the water in Areas 8 and 12 for foraging, although no food was present. All activities occurred below 1.5 m, demonstrating the maguari storks’ terrestrial nature (Kahl, 1971). None of the social displays described by Kahl (1972) were observed but mutual preening occurred twice. The gunite rocks in Area 10 and a dead tree in Area 4 were preferred by king vultures for resting and self-care. Feeding occurred on the ground in Area 3 below the tree in Area 4, minimizing the distance between resting and feeding sites. Use of trees and gunite cliffs in Area 10 is consistent with site selection in the wild; king vultures are characterized as forest and cliff dwellers (Olivares, 1965; Turner, 1974). Display behavior similar to the courtship sequence for Andean condors (Vultur gryphus) described by Gailey and Bolwig (1973) was observed once. A vulture walked toward a conspecific with neck bowed and wings held out and forward while the second bird crouched on the grass in Area 5. However, no copulation followed the display. Turkey vultures spent most of their non-feeding time in a dead tree above a terrestrial feeding station in Area 9. Feeding occurred on the ground as it

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does in the wild (Bent, 1963; Brown and Amadon, 1968). The species commonly occurs in groups in the wild, necessitating social behavior, but the three social display behaviors were never recorded. Threats (pecks) were occaslonaily directed at conspecifics and black vultures during feeding. Black vultures preferred the gunite cliff in Area 10 containing a food pan for carnivorous birds. They used the horizontal cliff surface for all behaviors twice as frequently as the dead tree in Area 9, which is consistent with their terrestrial nature in the wild. The gregariousness of the species resulted in two observations of mutual preening and one observation of a threat gesture (peck) directed at a conspecific (display - increase distance). Although unrecorded, threats (pecks) to turkey vultures occasionally occurred during feeding. Orinoco geese are known to perch in the wild (Delacour, 1954), but they were never observed above 1.5 m in my studies. The ground in Area 2 was the site of most of their activity. Since perching sites were available in the aviary and only two birds were pinioned, the terrestrial nature of the Orinoco geese is puzzling. Feeding (dabbling) occurred in the water (although Delacour (1954) reports they are never found in water) and at the food pan in Area 2. Individuals rested under a log and in a cave or the mud near the feeding stations; these sites probably had lower ambient temperatures than many other sites in the aviary. The species flocked in the aviary contrary to Phillip’s (1922) and Delacour’s (1954) observations that they live in pairs. Since two birds paired after the study was completed, flocking was not due to the geese being the same sex. Mutual preening occurred twice, and display - increase distance (head-low-and-forward posture; Johnsgard, 1961) was observed four times. Threat gestures were directed only at conspecifics. Even though Area 8 contained no feeding station, fulvous whistling ducks utilized Area 8 most frequently, standing in shallow water, on rocks or in mud while resting or engaging in self-care. The ducks used the pool in Area 8 and 12 for dabbling and diving but no food was present. The shade provided by bushes at the pool’s edge appeared to be the determining factor for the species’ use of Areas 8 and 12 for all activities. Fulvous whistling ducks are aggressive (Johnsgard, 1965), shown by the relatively high frequency of display - increase distance as the head-low-and-forward posture (Johnsgard, 1961). The species was usually found in a flock. Black-bellied whistling ducks used Areas 8 and 12 with almost equal frequency, probably because of the shade and water in these areas. The ducks were found most frequently on the ground, particularly on mud under bushes where temperatures may have been lower. Feeding was most frequent in Area 6 at a food pan and on bermuda grass in Area 9. Most frequent site use did not seem as closely associated with food as with the storks, vultures and geese. Black-bellied whistling ducks were less aggressive than fulvous whistling ducks, which is consistent with Johnsgard’s (1965) observations. Only two occurrences of the head-low-and-forward posture were recorded. The species flocked as shown by the high association number of 0.50.

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The eight species of birds showed specific utilization of environmental features depending on the location of appropriate food sources or regions where there were shade and water and probably lower temperatures. The substrates used appeared to be similar to substrates utilized in the wild. If a substrate utilized naturally did not occur in the aviary, the species used a foreign substrate nearest a food source or in a region of shade. Interactions of the two stork species are indicated by the mobile nature of the jabiru storks and the restricted use of areas by the maguari storks. The jabiru stork is larger than the maguari stork (Kahl, 1971) and may have in some way limited the movement of the maguari storks, resulting in the different space use patterns. Jabiru storks seemed to mutually avoid each other and the maguari storks, while the maguari storks showed conspecific flocking. Although king vultures were restricted in their use of the aviary, turkey and black vultures ranged over most of the areas. King vultures dominate other cathartids in the wild (Brown and Amadon, 1968) but in the exhibit were displaced by other cathartids, possibly due to their excitability and timidity in a captive situation. The association with conspecifics by the king vultures resulted in a higher association number than for the turkey and black vultures which showed no preference for conspecifics over heterospecifics. Interspecific aggregations during feeding have been noted for the latter two species in the wild (Parmalee, 1954; Brown and Amadon, 1968). The restricted movements of the king vultures and mobile nature of the turkey and black vultures contributed unique space use patterns to the community pattern. Orinoco geese and fulvous whistling ducks were restricted in their use of topographical regions. Mutual avoidance may have been operating between the two species because the most heavily utilized areas differed. The blackbellied whistling ducks were more mobile than the other anatids. During “threat bouts” the black-bellied whistling ducks displaced the fulvous whistling ducks in all cases. In the wild, black-bellied whistling ducks are also dominant over fulvous whistling ducks (Bolen, 1964), and they may have restricted movements of the Orinoco geese and fulvous whistling ducks as a result. The highest association numbers were calculated for the anatids, demonstrating strong flocking tendencies (attractive forces). Since there was little association with heterospecifics among the anatids, heterospecifics probably represented a neutral or repulsive social force. The uniqueness of species’ spacing patterns is partly demonstrated by the division of the aviary among the birds. The most frequently utilized areas usually differed among species. Jabiru storks and king vultures used Area 4 most heavily but at different heights. King vultures were also found frequently in Area 10 with black vultures but both species utilized alternative areas over 60% of the observed time. Most species associated with conspecifics rather than heterospecifics. These flocking tendencies represent a possible attractive force contributing to the community spacing pattern. Repulsive social forces existing among the birds cannot be predicted as easily from this study. The low association numbers

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for heterospecifics indicate a lack of association with other species but do not indicate the cause behind the phenomenon. Perhaps mutual avoidance was the repulsive force involved since little agonistic behavior was observed, In summary, both inanimate and animate factors were responsible for the spacing patterns in the captive bird community. Environmental factors possibly affecting species-specific space utilization were the location of food, the presence of shade and water, and similarity of sites to preferred natural sites. Social factors contributing to the community spacing pattern were probably conspecific flocking and mutual avoidance. Studies of the effects of environmental features and social forces on the behavior of captive populations will be important to the field of zoo biology. By observing species in an exhibit where a choice of environmental elements is available, one can determine species’ preferred sites for certain behaviors. If the species is to be housed in a smaller or less complex exhibit, the exhibit may be constructed to include preferred types of sites. In organizing mixed species displays, zoo personnel may benefit from knowledge of the interaction of environment and behavior of the species they are using. Compatibility of a group of species may be determined by noting the occurrence of interspecific agonistic encounters. A mixed species exhibit may be designed with preferred resting sites and feeding stations for any given species near each other. By appropriate structuring contact between incompatible species may be limited. The trend toward mixed species exhibits in modern zoos seems attractive to the visiting public but the exhibits must be designed with the physical and psychological welfare of the animals in mind. Studies of the response of species to environmental features and other animals in the exhibit can reveal factors which need to be considered in the exhibit design. ACKNOWLEDGEMENTS

This paper constituted my master’s thesis in zoology at the University of Oklahoma. A fellowship from the University of Oklahoma Research Institute made this study possible, and the Oklahoma City Zoo also provided monetary support during the execution of the study. Thanks are due to John Snelling for his cooperation and interest during the study and to Gary D. Schnell and Charles C. Carpenter for helpful criticism during the writing of this manuscript I am especially grateful to Bedford M. Vestal for his enthusiasm and helpful comments and suggestions during all phases of the study. REFERENCES Altmann, J., 1974. Observational study of behavior: sampling methods. Behaviour, 49: 227. 267. Bent, A.C., 1961. Life Histories of North American Birds of Prey, Part I. Dover Publications, New York, N.Y., 409 pp. Bent, A.C., 1963. Life Histories of North American Marsh Birds. Dover Publications, New York, N.Y., 392 pp.

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Bolen, E.G., 1964. Natural history of the black-bellied tree duck (Dendrocygna autumnalis) in southern Texas. Southwest. Nat. 9: 78-88. Bolen, E.G., 1967. The Ecology of the Black-bellied Tree Duck in Southern Texas. Dissertation, Utah State University, Logan, Utah, 138 pp., unpublished. Brereton, J.L.G., 1971. Inter-animal control of space. In: A.H. Esser (Editor), Behavior and Environment: The Use of Space by Animals and Men. Plenum Press, New York, N.Y., pp. 69-91. Brown, J.L. and Orians, G.H., 1970. Spacing patterns in mobile animals. Annu. Rev. Ecol. Syst. 1: 239-262. Brown, L. and Amadon, D., 1968. Eagles, Hawks and Falcons of the World. McGraw-Hill, New York, N.Y., 414 pp. Coles, V., 1944. Nesting of the turkey vulture in Ohio caves. Auk, 61: 219-228. Delacour, J., 1954. Waterfowl of the World, Vol. I. Country Life, London, 284 pp. Delacour, J. and Mayr, E., 1945. The family Anatidae. Wilson Bull., 57: 3-55. De Schauensee, R.M., 1964. The Birds of Colombia. Livingston Publishing, Narberth, Pa., 427 pp. Gailey, J. and Bolwig, N., 1973. Observations on the behavior of the Andean condor (Vultur gryphus). Condor, 75: 60-68. Gilliard, E.T., 1958. Living Birds of the World. Doubleday and Company, Garden City, N.Y., 400 pp. Grossman, M.L. and Hamlet, J., 1964. Birds of Prey of the World. Clarkson N. Potter, New York, N.Y., 496 pp. Heath, J.E., 1962. Temperature fluctuation in the turkey vulture. Condor, 64: 234-235. Hediger, H., 1964. Wild Animals in Captivity. Dover Publications, New York, N.Y., 207 pp. Johnsgard, P.A., 1961. The taxonomy of the Anatidae - a behavioral analysis. Ibis, 103: 71-85. Johnsgard, P.A., 1965. Handbook of Waterfowl Behavior. Cornell University Press. Ithaca, N.Y., 378 pp. Kahl, M.P., 1971. Observations on the jabiru and maguari storks in Argentina, 1969. Condor, 73: 220-229. Kahl, M.P., 1972. Comparative ethology of the Ciconiidae. Part 4. The “typical” storks Dissoura and Euxenura). Z. Tierpsychol. 30: 225(genera Ciconia, Sphenorhynchus, 252. Kahl, M.P., 1973. Comparative ethology of the Ciconiidae. Part 6. The blacknecked, saddlebill, and jabiru storks (genera Xenorhynchus, Ephippiorhynchus, and Jabiru). Condor, 75: 17-27. King, J.A., 1970. Ecological psychology: an approach to motivation. Nebr. Symp. Motiv., 18: l-33. Kummer, H., 1971. Spacing mechanisms in social behavior. In: J.F. Eisenberg and W.S. Dillon (Editors), Man and Beast: Comparative Social Behavior. Smithsonian Institution Press, Washington, D.C., pp. 221-233. McBride, G., 1964. A general theory of social organization and behaviour. Univ. Queen& Pap. Fat. Vet. Sci., 1: 75-110. McBride, G., 1971 a. The nature-nurture problem in social evolution. In: J.F. Eisenberg and W.S. Dillon (Editors), Man and Beast: Comparative Social Behavior. Smithsonian Institution Press, Washington, D.C., pp. 37-55. McBride, G., 1971 b. Theories of animal spacing: the role of flight; fight, and social distance. In: A.H. Esser (Editor), Behavior and Environment: The Use of Space by Animals and Men. Plenum Press, New York, N.Y., pp. 53-68. McIlhenney, E.A., 1939. Feeding habits of black vultures. Auk, 56: 472-474. Mason, W.A., 1968. Use of space by Callicebus groups. In: P.C. Jay (Editor), Primates: Studies in Adaptation and Variability. Holt, Rinehart and Winston, New York, N.Y., pp. 200-216.

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