Bower birds, bones and archaeology

Bower birds, bones and archaeology

Journal of Archaeological Science 1986,13,307-3 18 Bower Birds, Bones and Archaeology Su Solomon”, Monica Minnegal” and PeterDwye? (Revised ms. acce...

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Journal of Archaeological

Science 1986,13,307-3 18

Bower Birds, Bones and Archaeology Su Solomon”, Monica Minnegal” and PeterDwye? (Revised ms. accepted 13 September 1985) Objects collected by the Australian great bower bird, Chlamydera nuchalis, may include artifacts and human food debris. The birds could affect the shape and interpretation of some archaeological assemblages. Bones from two bower collections are described according to: (1) their sizes and shapes; (2) the taxa and elements represented; and (3) marks and damage. The potential relevance of the birds for archaeological interpretation is assessedand ways of recognizing bias caused by the birds are discussed. BOWER BIRDS, FAUNAL ASSEMBLAGES, SITE DISTURBANCE, TAPHONOMY.

Keywords:

Introduction The bower . . . is adorned with quantities of grey and white pebbles, shells of land molluscs, and, on the sea-coast, with marine shells and dead Polyzoan colonies, as well as with native fruits, fragments of leaves,galls, and rosette-like growths of plants, and odds and ends gathered from the native camps. Although the bowers of these birds are often built close to native camps, the birds are not molested. (Thomson, 1935: 76) . . . the decorations are very profuse, and consist of bivalve shells, crania of small mammals and other bones bleached by exposure to the rays of the sun or from the camp-fires of the natives. (Gould, 1865: 451) Much archaeological work has examined the importance of carnivores and scavengers in removing and destroying parts of fauna1 assemblages (e.g. Hope, 1973; Hill, 1976; Haynes, 1980; Binford, 1981; Walters, 1984). Recognition of the activities of these animals depends on, first, the type of damage they cause to carcasses or to isolated bones

and, secondly, the presence or absence of certain skeletal elements. To date, little attention has been directed to the role of birds in biasing archaeological sites. Cane (1982) has reported that a bird, the Australian bustard, may remove stone artifacts from open archaeological sites. The birds use the stones as gastroliths. Jones & Allen (1978) have ‘Department of Prehistory and Archaeology, University of New England, Armidale,New SouthWales,Australia2351. *ZoologyDepartment,Universityof Queensland,StLucia, Brisbane,Queensland, Australia4067.

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shown that seabird “middens” could sometimes be mistaken as archaeological sites. Raptors can affect assemblages when they regurgitate pellets containing bone (Hope, 1973). Removal of bones from both open and shelter sites by birds could also be important (see, for example, Horton, 1978). In the northern hemisphere, jays, jackdaws and magpies could have removed bone from open sites and in Africa the bearded vulture or Lammergeyer visits animal carcasses where it swallows small bones and removes, smashes and eats large bones (Austin, 1962). In Australia, crows and black kites have been reported to scavenge sites (Walters, 1984), and there are species of bower bird which collect many bones. This paper concerns the influence bower birds could have on archaeological sites and their interpretation. Bower birds are Australian and New Guinean passerines which, together with birdsof-paradise, comprise the family Paradisaeidae. Adult male bower birds of the genera Priondura, Ptilonorhynchus, Sericulus, Chlamydera, Amblyornis and Archboldia construct bowers, either “avenues” or “maypoles”, from sticks, twigs and grass and use these as foci for displays and mating (Marshall, 1954; Gilliard, 1969). Objects of many kinds, both natural and artifactual, are collected by the birds and placed in and near the bowers. The objects are frequently manipulated during displays. Many hundreds of objects may be present at a single bower and male birds sometimes plunder the collections of other males to decorate their own bowers. Within Australia the spotted bower bird (Chlamydera maculata) is distributed through the central interior of the continent from west of the Great Dividing Range to the west coast; the related great bower bird (Chlamydera nuchalis) is widespread across northern Australia (Pizzey, 1980). These species occur in drier open woodlands and inland scrubs and are more abundant where water is available. They are moderately large with total lengths of 250-375 mm (cf. common and bluejays of the Northern Hemisphere). Both tend to be sedentary in habit, with the spotted bower bird common at only some localities within its extensive range and the great bower bird generally common. In areas where the latter species is abundant the bowers of individual males may be less than 1 km apart. Males build bowers of the “avenue” type and decorate these with many reddish, whitish or shiny objects together with droppings of mammals. Mollusc shells, bleached bones, stones, pale leaves and green fruit dominate the collections, which often include more exotic items such as gastroliths from birds, brokenglass, shotgun cartridges, nails, aluminium ring-pulls, coins and, in one reported case, a bushman’s glass eye (Marshall, 1954; Warham, 1962; Pizzey, 1980). Some of the shell, bone and stone found at bowers is the remnant of human activity, both prehistoric and historic. Collections of bone from individual bowers of spotted bower birds may include more than 1000 pieces and, for both species, collections of stone may weigh several kilograms (Chaffer, 1984). Both these species of bower bird “paint” twigs within the avenue using saliva mixed with coloured substances from plants. Objects found at bowers are often tinted by “paint”. There are three ways in which the behaviour of spotted and great bower birds could have relevance for archaeology. First, an abandoned, decomposed and dispersed collection of bower objects could be misinterpreted as an open archaeological site. Secondly, because bower birds include artifacts and human food debris in their collections they could, through selective removal, I bias the composition of archaeological assemblages. The abundance of snail shells at some bowers indicates that the birds will collect objects from enclosed spaces; thus removal of material from both open and shelter sites is possible. Thirdly, bower bird assemblages could contaminate sites either through their proximity to those sites or by natural or human mixing of bower bird and archaeological assemblages. Bower objects could, for example, have been a source of children’s playthings; indeed, early explorers thought that the bowers of some species were the playhouses of native children (Austin, 1962).

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The wide distribution of spotted and great bower birds across northern and inland Australia and the fact that bower birds, like people, prefer to live near water accentuates the potential archaeological relevance of these animals. In this paper we provide an initial characterization of two assemblages of bone from bowers of the great bower bird and discuss the significance of the observations for archaeology. The Sites

On 24-25 December, 1984 all vertebrate bone was removed from two bowers of great bower birds. Other objects observed at the bowers, but not collected, included shells from land snails, portions of shell from freshwater mussels (probably of prehistoric origin), gastroliths from birds, stones (including at least 80 artifacts), green fruit, macropod droppings and an assortment of material from the abandoned camps of Europeans (e.g. glass, teapot lid, flagging tape). One of the bowers (BR) was at Black Rock, a weathered sandstone outcrop approximately 800 x 400 m, in north-eastern Queensland (19”Ol’S, 144”28’E). The second bower (LBR) was approximately 1.5 km north-north-west of the first bower on a different and smaller outcrop of sandstone (Little Black Rock). The outcrops occurred in a gently undulating plain supporting an open woodland of low eucalypts. Vegetation on and adjacent to the rocks was richer in species and denser than vegetation away from the rocks; some deciduous vine thicket occurred along the eastern cliff of Black Rock. The rocks and surrounding woodland supported a diverse vertebrate fauna. A population of 100 or more plain rock wallabies (Petrogule inornata) is present on Black Rock and, at times of drought or fire, this rock is important as a refuge habitat for many birds (Dwyer, 1972). Mammals recorded on or near the rock are echidna (7’achyg~ossus aculeutus), brush-tailed possum (Trichosurus vulpeculu), two species of small ( < 5 kg) macropods (Aepyprymnus rufescens and Petrogule inornutu), three species of large ( > 15 kg) macropods (Macropus gigunteus, Mucropus robustus and Mucropus antilopinus), a small rodent (Ruttus tunneyi), several small bats, dingo, fox, cat, hare, pig, cattle and horse. The last two species are present as domestic stock. The Assemblages Shapes and sizes

Bower birds are interested in bones as objects in themselves. Any selectivity in their collecting activities will be based on attributes of the bones rather than on attributes of the animals or parts of animals the bones once supported. We examined three attributes of the bones. Weight and length, which could influence both portability and effectiveness in display, were measured in grams and millimetres respectively. For each bone we measured maximum length irrespective of anatomical orientation or breakages. The cross-section of a bone was considered an important influence upon manipulability; it was indexed as the ratio of maximum length to weight where lower index values represent higher values for cross-section. Figure 1 records frequency distributions for each attribute for the two bower assemblages BR and LBR. BR contained 160 bones with a total weight of 98 1 g, and LBR contained 159 bones with a total weight of 866 g. The weight of collected bones was strongly constrained. All bones were less than 30 g; 84% of those from BR and 83% of those from LBR were less than 10 g. The lengths of bones were more variable but all were less than 190 mm and, for both bowers, 81% of bones were between 20 and 90 mm. Index values for cross-section ranged from 2.5 to 300 mm/g (excluding one extreme value for a minute fragment) with 94% of BR bones and 75% of LBR bones yielding values below 30 mm/g. Within these broad constraints the frequency distributions for weight, length and cross-section differ between the

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40 20

L

IO

20

50

30

100

150

60

LBR 6ohr

(b)

u” 40 5 & h 20

40

20 L

20

40

:j-rL; IO 20 Weight (g)

:

60 (cl m

50

100 Length (mm)

150

30 Cross-section

60 90 index (mm/g)

Figure 1. Frequency distribution of bones found at two bowers (BR and LBR) by (a) weight, (b) length, and (c)index to cross-section.

Table 1. Relationship between cross-section index and weight for bones from two great bower bird bowers. Cross-section index is length (mm)lweight (g) Number of bones with cross-section index in stated range (mm/g) Black Rock Weight(g)

ck2.5 2.5-5.0 5(rlO~O 3 10.0 Totals

Little Black Rock

@-IO

IO-20

> 20

k-10

l&20

> 20

1 21 31 21 74

17 20 16 4 57

16 13 0 0 29

1 12 18 2s 56

5 13 12 2 32

49 20 2 0 71

assemblages. This difference is diminished if weight and cross-section are examined together (Table 1). As the index to cross-section increased the average weight of collected bones decreased. In both assemblages the heaviest bones are “chunky” (i.e. broad and thick for their length) and the lightest bones are “slender” (i.e. narrow for their length). The bower birds had not collected “chunky” bones that were light or “slender” bones that were heavy. Figure 2(a) and (b) provides scatter diagrams of cross-section against weight for the bones of each bower. The two scatters overlap completely. This overlap is shown on Figure 2(c); the two curves drawn on Figure 2(c) enclose the universe of possible values for objects with lengths between 10 and 190 mm and with weight less than 30 g. Clearly, the bones found in the bower assemblages are a biased sample of all possible objects conforming to these defined limits of length and weight, The relationship between length (L 6 190 mm) and weight (W G3Og) for bones found in the bower assemblages (using pooled data) may be expressed by the formula 1ogJ = a+0*38log, W, where a varies

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120 (c) 100

100

*fI

00. IT-60

...

IO Weight

(g)

Figure 2. Scatter diagrams of cross-section against weight for bones from (a) BR bower, (b) LBR bower, and (c) pooled data. The curves drawn on Figure 2(c) enclose the universe of possible values for objects with lengths between 10 and 190 mm and weight less than 30 g.

between 3.0 k.O.44 and 3-9 k 0.33 according to bone type (i.e. lower values of a are for tarsals and epiphyses, higher values are for ribs and portions of long-bone shafts). This formula accounts for 74.4% of the variation in the data. We regard this formula as an approximate descriptor of the sorts of bones likely to be selected by great bower birds. While assemblages of bone found at different bowers might differ greatly in terms of the frequency distribution of single attributes-with, for example, all bones “slender” at one bower and all bones “chunky” at another-items within those assemblages should conform to the rule embodied in the formula above. Species and elements Because bower birds are selective in their choice of bones it is likely that available animal species or skeletal elements will be differentially represented in bower assemblages. Table 2 classifies the assemblages by taxonomic group and skeletal element. All the bones came from mammals. This occurred despite the local presence of many species of frog, reptile and bird. The absence of skeletal material of some species of frog, reptile and, among mammals, the echidna may reflect a tendency for the animals to die in situations (e.g. burrows, rock crevices, hollow logs) that are inaccessible to bower birds. The carcasses of other species, because they are small, may be scavenged in greater proportion or in their entirety (cf. Walters, 1984). But it may also be the case that the attributes of many bones of non-mammalian species place them outside the domain of acceptability described by Figure 2; this could be true of bird bones which, relative to those of mammals, tend to be light for their size. The same types of skeletal elements were found in each assemblage but their proportional representation in those assemblages was very different. Ribs and rib fragments, which are long slender bones, comprised 3% of the BR assemblage and 21% of the LBR assemblage. Tarsals and phalanges, which are short chunky bones, comprised 27% of the BR assemblage and only 13% of the LBR assemblage. At least part of the difference between the bower collections may reflect patterns of availability of bone at Black Rock and Little Black Rock respectively. In December 1984 several carcasses of macropods were found at Black Rock. The thoracic region and forequarters of these

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Table2. A classification of the bones from Black Rock according to taxa* and element

uM Skull Cranial vault Maxilla Mandible Jaw fragment Tooth Vertebra Anterior Posterior Portion Rib Scapula Humerus Epiphysis

1M

Black

Rock

sM

D

Totals MN1 values

Little C

3

Total

uM

IM

sM

M

at Black

Black TV

Rock

and Litrle

Rock F

P

H

R

Total

I

3 2 1 1

3 3 1

I

1

2 1 1 5

I 10

I 2

1 2

99 10

1

1 2

2

9 6 3

5

3

3

I

4 19 12 1

2 5 2

1

11 12 1 I

5 8

1 1

6

1

22 4

12 2

2 1

33 1

1

5 9

16 25

32

3

2 2

5 18

4

6

4 19 12 I 9 10 1 I

14

1 2

5

9 I 3

5

1 I

2 2

3 12 3 5 1 2 1 2 2 11

1

Shaft

Radius Ulna Pelvis Femur Epiphysis Shaft Tibia Epiphysis Shaft Fibula Tarsal Astragulus Calcaneum Cuboid Other Metatarsal 4th 5th 4th, epiphysis Phalange Fragment Long-bone Other

the bowers

1 1 3 I

1 1 6

6

1 9

I

5 1 5

1

16

22 1

160 17

61

1

2 8 2

2

6 9 1

8 22 1

63 4

20 3

5

2 1

1 1

5 1

1 1

1 1

159 12

*Taxa are coded as follows: uM, unidentified mammal; IM, large macropod; sM, small macropod; M, macropod;Tv, brush-tailed possum; D, dog; F, cat; P, pig; C, cow; H, hare; R, rat. Taxa not represented in an assemblage are excluded from the relevant portion of the table. Anterior vertebrae are cervicals and thoracics; posterior vertebrae are lumbars, sacrals and caudals. Long-bone “shafts” include those with and without attached epiphyses.

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carcasses had been removed or damaged by scavengers and, hence, bones associated with these anatomical portions would not become available to the birds. The sorts of skeletal elements found in the bower assemblages differed between taxonomic groups. The differences correlate with the sizes of the animals concerned. Thus tarsals, phalanges, epiphyses of long-bones and vertebrae were almost all from large macropods. By contrast, pelves and long-bone shafts tended to be from small macropods or other small animals such as brush-tailed possum, young dog and cat. This pattern is understandable within the frame of Figure 2: “chunky” bones of small animals would be too light and unbroken long-bones of large animals would be too heavy to be acceptable to bower birds. The percentage of identifiable bone in the assemblages was extraordinarily high compared with results usually obtained for bone from archaeological sites. At least 90% of the bones in BR and 86% of those in LBR were identifiable to element; 84 and 58%, respectively, were identifiable to taxonomic group. Had a better comparative collection been available these percentages could have been improved. Marks and damage

Many bones in the bower collection were weathered or had signs of marks and damage from bower birds and other sources. Table 3 catalogues these data and Table 4 records the distribution of marks made by the birds among different types of bone. There were no pronounced differences between bowers in the observed patterns of weathering and marking of bones. The data in Table 4 show that some categories of bone, especially tarsals and the epiphyses of long bones, were less likely than other bones to have been marked by the birds. These differences may reflect less use of some types of bone during displays at the bower. Most of the bones were weathered. These were white with longitudinal cracks and the surface was often flaked. Some had been weathered on only one side. These features Table 3. Weathering and marks on bones from two great bower bird assemblages. Marks were recorded as present only where they were unambiguous. Values indicate the number of bones with weathering or marks ofparticular kinds. There are no data for two bones from Black Rock and one from Little Black Rock

Black Rock Weathering Absent Light Heavy Bower bird marks Handling gloss Beak marks Pseudo-punctures Breakages Source of other marks Rodent Cat Fox Canid Pig Human cut marks Unknown, probably human

Little Black Rock

14 96 48

19 72 67

118 7 4 31

132 32

1 5 2

12 2 5 2

-

1 I

-

1

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Table4. Bower bird marks bowers combined

found

on different

Bone type

.n

Ribs, long-bone fragments Lone-bone shafts. metatarsals Vertibrae, phalanges, calcanea Other tarsals, epiphyses Skull portions, scapulae, pelves

16 82 83 44 31

categories

of bone:

Proportion with handling gloss 0.83 0.96 0.84 0.32 0.11

dara from

two

Proportion with beak marks, pseudo-punctures or breakages 0.28 0.32 0.21 0.05 0.13

indicate that most bones had been collected from open areas. Two fragments of longbone from BR were heavily stained brown and, presumably, had once been buried. Two other sorts of staining were present on most bones; patches of brown, 3-5 mm in diameter, apparently derived from bones lying on soil or in vegetation, and larger areas of “pink” derived from the birds “painting” bones with a vegetable dye. The latter stains were not as intense as the former and appeared to have been applied on more than one occasion. Marks and breakages resulting from bower bird behaviour were distinctive and are described below. Gloss: Gloss was the most common mark left on bones by bower birds (79% of bones affected). It was a result of repeated handling of bones by the birds. Although visible to the naked eye gloss was best observed and identified by light microscopy. The affected area of bone had lost its periosteum, developed a distinctive sheen and often contained embedded sand grains. Gloss usually occurred at the ends of long bones and in the middle of shorter, chunky bones. Beak marks: These were observed on only seven bones. The marks were not unlike ones left by mammalian carnivores. They had two distinguishing features. (1) The mark had no beginning or end. Whereas marks left by carnivores have an impact point at one end and glide off at the other end, these marks had the impact point at the centre of the run and tapered smoothly to either end. (2) At the central impact point the bone was ridged, apparently as a result of even and sustained pressure from the bird’s beak. This feature was quite unlike the marks left by mammalian teeth which furrow bone to produce “shoulders” either side of a mark. Pseudo-punctures: Four bones had been marked by sharp jabs from the tip of the bird’s beak. These marks had fracture planes where the surface had been pushed into the bone and, unlike punctures from mammalian teeth, they lacked ridges or craters at the periphery of the jabs. Breakages: Some breakages to the bones had straight fracture planes and showed some shattering and splintering. These bones had been broken when old and dry, presumably by the birds. Shattering appeared to have been caused by an impact “jab”. The jab mark was often visible and some of the broken bones had embedded splinters. Some long bones that carried gloss at one end (usually the heavier end) had, in fact, lost their other end as a result of handling by bower birds.

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Archaeological Implications

In introducing this paper we suggested three ways in which bower bird behaviour could have relevance for archaeology. Here we examine these possible influences. For each, we ask whether the postulated archaeological connection is sustained, show how bower bird influence might be recognized for cases where the influence is sustained and comment on the response archaeologists should make. (1) Could an abandoned, decomposed and dispersed collection of bower objects be misinterpreted as an open archaeological site?

Great and spotted bower birds often construct bowers in situations prone to intermittent flooding (G. Ingram, pers. comm.). Flooding could scatter and bury collections of bower objects at locations such as creek and river banks known to have been favoured by Aborigines. The association of stone artifacts, human food debris (e.g. mussel shell, bones with cut marks) and bone of non-human provenance could promote misinterpretation of the scatter of bower objects. We think it less likely that abandoned bower collections from situations not exposed to flooding could be buried sufficiently rapidly for any of the bone to survive long periods. Bower bird influence of the sort noted here may be more likely in coastal situations since the archaeological longevity of bone appears to be increased when that bone is associated with shell deposits (cf. Alfredson, 1983). The distribution of the birds indicates northern coastal situations as a potential problem area for misinterpretation. The sorts of bones found at the bowers of great bower birds exhibit certain physical properties (e.g. ranges of weights and lengths) which are best characterized by the scatter diagrams shown on Figure 2 and by the equation describing those scatters. We think that collections of bone which conform to this equation are unlikely to be of human provenance. It is important to stress that the bones found at a particular bower need not fill the entire scatter shown in Figure 2. A single collection could be strongly biased for bones from only a portion of the distribution; this will be a function of the bones available to the bird. A relatively narrow variance about the mean obtained from distributions of weight or length for the bones would also imply that human activity was not at the source of the collection (e.g. Hope, 1973) but would not directly implicate bower birds. In contexts where the activity of bower birds could be expected, archaeologists may assess the status of sites (i.e. human or bower bird) by recording weights and greatest lengths of all bones and testing relationships among these variables against the curves and equation presented here. If the bones are archaeological many will yield values lying within the field depicted on Figure 2; that is in the nature of bones of particular kinds. But the scatter of values from bones in an archaeological collection may be expected to reach well beyond the limits we have described for the bones found at Great Bower Bird bowers. (2) Could bower birds, through selective removal, bias the composition of archaeological assemblages?

This possibility is clearly sustained by the data in this paper. Three sorts of observation are pertinent. First, the presence in modem bowers of some bone from former archaeological deposits, together with stone artifacts, fresh water mussel shell and snail shells demonstrates that the birds do remove objects from both open and shelter (or overhang) sites. Ethnohistoric sources reinforce these observations in regard to open sites at least (Gould, 1865; Thomson, 1935). Secondly, analyses of the bower collections indicate preference by the birds for bones with particular characteristics. Many of the preferred

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bones have properties which would make them relatively resistant to processes of diagenesis (cf. Binford & Bertram, 1977). They are stocky and compact with little of their internal structure cancellous (e.g. bones from the pes or portions of the stronger limb bones). Bones of this sort tend to be, and remain, more readily identifiable both to element and to species than are many other bones. Removal of even a few bones from an assemblage could distort minimum number (MNI) estimates. Thirdly, the sorts of skeletal elements found at bowers differ between different species of mammal with slender bones, such as long bone shafts and ribs, usually from smaller mammals and chunky bones, such as tarsals, usually from larger mammals. If this sort of bias on the part of the birds was reflected in archaeological assemblages the result could be skewed interpretations regarding portions of carcass favoured by people or differential treatment of portions by people. Minnegal (1984) has described archaeological assemblages of dugong from Princess Charlotte Bay, North Queensland, Australia. A collection of 253 adult dugong bones did not include any caudal vertebrae, radii, ulnas or elements from the manus (carpals, metacarpals and phalanges). For caudals and phalanges particularly, and for carpals and metacarpals to a lesser degree, these absences were statistically pronounced based on expectations derived using MN1 values. Minnegal(1984: 65) suggested that: “Some selectivity appears to have been employed in deciding the portions to be brought to, and/or subsequently removed from, different locations.” She did not consider the possibility that the selectivity could have been that of bower birds. (Great bower birds are common at Princess Charlotte Bay.) We have obtained weights and lengths from 19 manus bones and eight chevron bones of an adult dugong. All these bones yielded values which fell within the scatter of points shown on Figure 2; they could have been removed by bower birds. (We note the improbability that all these bones would have been collected by a bird but offer the counter-argument, from our own observations, that the birds will sample repeatedly from particular bone scatters.) To sustain her position Minnegal would need to structure the argument differently. Bower bird influence arising from selective removal may be suspected or recognized only where fauna1 analyses record the sizes and shapes of elements and identify elements as well as taxa. Where particular sorts of elements are represented less often than might be expected and have attributes within the range chosen by bower birds then the latter may have influenced the assemblage. Again, skewed distributions of elements, particularly different patterns of skewing between different size categories of taxa, may implicate bower birds. The data in Table 2, showing the sorts of elements the birds may select from different taxa, provide a first step toward assessing such implications. To identify potential bias arising from selective removal by bower birds analyses of fauna1 assemblages must be continued beyond the level of estimating and identifying MNIs of represented taxa. (3) Could bower bird assemblages contaminate archaeological sites?

Given that bower collections may be located near the living places of people this possibility is upheld. It would be manifest where: (1) extrinsic factors (e.g. flooding) mixed bower objects with archaeological material; (2) people (or dogs) moved objects; and (3) the boundary between the domains of humans and bower birds was indistinct or not recognized. We suspect contamination of these kinds to be a less likely problem for archaeologists than those discussed above. Where archaeological and bower assemblages are contiguous the physical attributes of bones in the latter should allow definition of boundaries. Contamination of archaeological sites by bower objects may be recognized only by examining marks on bones. The presence of many bones with gloss, or of some bones with marks (beak marks,

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pseudo-punctures) or breakage patterns of the kinds described above would indicate mixing. Both the gloss and the breakage patterns produced by bower birds are likely to be diagnostic; the latter are unlike patterns which result when people damage bone (e.g. during eating or by trampling) or patterns caused by dogs or the Tasmanian Devil Surcophilus harrisii (Douglas, Kendrick & Merrilees, 1966; Binford, 1981). These observations suggest the sort of recording archaeologists must make to untangle this potential bower bird influence. There is, of course, an added dimension to the problem of contamination. Just as bower birds plunder each others’ collections and establish “trading networks” which might disperse bower objects across considerable distances, so bower objects found in archaeological collections may have derived from those collections. We have shown that the great bower bird could influence the shape and interpretation of Australian archaeological assemblages. It joins a growing list of animal species which can make an archaeologist’s life hazardous. Bower birds differ in one important way from other “site scavengers”. They move bone after it has lost interest as food; their contribution to site disturbance is made at about the phase when archaeologists may have thought things were settling down. The birds may differ in another way in that they, more than other scavengers, move bones of particular kinds; that is, bones that might have had considerable archaeological longevity. We have suggested how the various potential influences of bower birds might be recognized. It is important to say that recognition of these influences or analogous ones arising from other animal species need not require much more data recording than is commonly done. For the most part archaeologists do record the relevant data. Our plea is for more rigorous analyses and for publication of more detailed information than species lists and MN1 estimates. [From Australia there were few published reports other than Minnegal (1984) where sufficient data were provided to test the possibility that bower birds may have distorted results.] This plea is not merely on behalf of a handful of workers who are enchanted by bower birds. Many species of birds and mammals may modify the contents of hunter-gatherer habitation sites. Their impacts will have been varied but need to be assessed, if only to exclude them as unimportant. Studies of the sort we have described may show where biases can arise and how they might be recognized. This would greatly assist assessment of site disturbance and thus improve understanding of archaeological fauna1 assemblages.

Acknowledgements

We thank Tony Barnes, Science Faculty, University of Queensland, for advice and assistance with statistics, and Malcolm Abel, Department of Prehistory and Archaeology, University of New England, for assistance with fauna1 identification. References

Alfredson, G. (1983). St Helena Island-a changing pattern of exploitation. Australian Archaeology

17,79-86.

Austin Jr, 0. L. (1962). Birds ofthe World. London: Paul Hamlyn. Binford, L. R. (198 1). Bones: Ancient Men and Modern Myths. New York: Academic Press. Binford, L. R. & Bertram, J. (1977). Bone frequencies and attritional processes.In (L. R. Binford, Ed.) For Theory Building in Archaeology. New York: Academic Press,pp. 77-153. Cane, S. (1982). Bustard gastroliths in the archaeological record. Australian Archaeology 14, 25-34. Chaffer, N. (1984). In Quest of Bower Birds. Melbourne:

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