FOOD CACHING IN THE TROPICAL FRUGIVORE, MACGREGOR'S ( MACGREGORIAE)

M. A. PRUETT-JONES1 AND $. G. PRUETT-JONES1 Museumof VertebrateZoology and Department of Zoology,University of California,Berkeley, California 94720 USA

AI•STRACT.--Malesof MacGregor'sBowerbird (Amblyornismacgregoriae) cache fruit. In a study population in easternPapua New Guinea we found 437 cachesites at 39 bowers.Adult malesstored an averagetotal of 17.6 fruits (range 0-82) at 13.6sites (range 0-55), significantly more than immaturemales. All siteswere locatedin vegetationabove ground within 13 m horizontal and 9 m vertical distancefrom the males'bowers. For 3 malesstudied intensively, the rate of replacementof cachesaveraged 0.13 replacements.site-:.day-•, with no signifi- cant differencesamong males. Caching occurredonly during the seasonalperiods of bower attendanceand breeding activity. Femalesdid not store fruit and did not take fruit stored by males.We suggestthat by extendingthe time malescan remain at their bowers,caching may increaseinteraction time with femalesand decreaserates of bower maraudingby rival males. There was no evidence that cachedfruits served as bower decorations.Received 7 May 1984, accepted4 October1984.

FOODstoring refers to the depositionof food changesin food abundancein temperatehab- items in a particular location for later con- itatsand the coolertemperatures that allow for sumption.It hasbeen observedin a number of storageof perishableitems over a longer peri- and mammal species(Roberts 1979, Van- od of time (Roberts 1979, Vander Wall and Bal- der Wall and Balda 1981, Smith and Reichman da 1981).Nonetheless, tropical jays (Turaek and 1984). In , food storage occurs as either Kelso 1968) and woodpeckers (Skutch 1969) a long-termstrategy, to yield foodduring times storefood, as do their temperatecounterparts, of scarcity,or on a short-termbasis for tempo- particularly in montane areas. rary retention or accumulationof items that In this paper we describefood-storing be- cannot be eaten at one time. havior in MacGregor's Bowerbird (Amblyornis Long-termfood storageoccurs predominate- macgregoriae),a frugivorous speciesfound in ly in nonmigratoryspecies and in habitatswith montane rain forest in New Guinea. This be- seasonal fluctuations in resource abundance havioris separatefrom fruit gatheringby males (Roberts 1979, Smith and Reichman 1984). for bower decoration.We present data on oc- The food storedis generally durable and par- currence,type, location, and replacementrates ticulate, such as seeds.Birds for which long- of storedfood items and discusscaching in re- term food storageis an important contribution lation to the species'social organization and to reproductivesuccess and winter survival in- bower-buildingbehavior. Food storing has not clude woodpeckers (Koenig 1978), corvids been describedpreviously in any bowerbird or, (Tomback 1977, Bossema1979, Vander Wall and to our knowledge, any tropical frugivorous Balda1981), and parids(Ulfstrand 1976,Sherry passefine.

et al. 1982).Short-term food storageis known METHODS primarily in shrikes (Laniusspp., Craig 1974) and birds of prey (Newton 1979, Walter 1979) Our observations were made on the southwestern and in somecracticids, parids, and corvids(Piz- slopeof Mt. Missim, Kuper Range,Morobe Province, PapuaNew Guinea (7ø16'S,146ø47'E). The study area zey 1980, Smith and Reichman 1984). comprised750 ha of primary,midmontane rain forest Long-termfood storing apparentlyis more between 1,450 and 2,200 m altitude and included three commonin temperatethan in tropical avifau- drainagesand the ridge lines separatingthem. An- has (Smith and Reichman 1984). This may nual rainfall averaged about 2,000 mm, and daily reflectboth the greaterimportance of seasonal temperaturesvaried from 9ø to 25øC.More detailed descriptionsof this areaare presentedin Pruett-Jones and Pruett-Jones (1982) and Pratt (1983). • Present address:Department of Biology, C-016, Observationson MacGregor'sBowerbird were made University of California at San Diego, La Jolla,Cali- during 21 monthsof fieldwork betweenAugust 1980 fornia 92093 USA. and December1983. We first discoveredcaching in

334 The Auk 102: 334-341. April 1985 April1985] BowerbirdFruit Caching 335 this speciesin September1982. Most data presented As part of other studies(Pruett-Jones unpubl. data), here were gathered during the 6-week period from we monitored activity at bowers weekly or biweekly 17 October to 4 December 1983. throughout 1982 and 1983. These recordsprovided Caching behavior of 3 adult males that maintained data on the relative seasonal occurrence of fruit cach- adjacentbowers on a single ridge was studied in de- ing and its relation to bower maintenanceand breed- tail. We visited these 3 bowers 4 times over the course ing. of ! week and mapped and marked the cache sites before the start of regular sampling.We define a cache RESULTS site as a specificlocation where one or more fruits, of one or more species,were stored. If a structure (e.g. a small tree) had fruits cachedin several loca- Generalbiology and cachingbehavior.--On av- tions, each location was considered a separate site. erage, 47 (range = 43-54) male MacGregor's Changesin the number and speciesof fruits at each were active on our study site each cache site were recorded from 3 to 22 November. season from 1980 and 1982. Adult males con- Sites were checked twice daily, between 1100 and struct a maypole bower (twigs piled up around 1300 and between 1600 and 1800. To facilitate an ac- a slender sapling) that is decoratedwith fruit, curate measure of replacement, all cached fruits fungus, charcoal, and insect frass. Immature within reach of the observer (up to 3-4 m vertical malesbuild rudimentary structuresthat may be height) were marked with small spots of nontoxic abandoned after a few weeks of use. paint, and those fruits out of reach were noted for color or variety. Bowers were regularly and linearly spaced A cachereplacement was defined as a decreasefol- along ridge-line habitat, with a mean inter- lowed by an increasein the number of fruits at the bower distanceduring the 1980 and 1981 sea- site, or vice versa,irrespective of the number of fruits sons of 182.8 m (n = 98, range = 60-423, SD = involved (i.e. a replacement occurredwhen the male 72.9). The local placement of bower sites ap- removed some or all of the fruit at a cache site and pears to be determined primarily by habitat then replacedit, or added fruit and then removed it). characteristicsof the ridge line (Pruett-Jones Fruit changerefers to the absolutenumber of remov- and Pruett-Jones 1982). Observations of marked als of marked fruits and replacementsof unmarked males in 1980 indicated that they spent an av- fruits at each site. Some new caches were discovered erageof 54%(range = 20-75%) of daylight hours near the study bowers after initiation of sampling. within a 20-m radius of the bower, and this In our analysisof replacementrates, we include only core area was aggressivelydefended. those sites that were monitored for at least 8 days (about the maximum length of time over which a A. macgregoriaewas primarily frugivorous; replacement might occur). Basedon direct observa- 95% of its diet consisted of medium to large tions of males eating cached fruits (see Results), we drupes and, to a lesser degree, arillate fruits. assumedthat only the resident male was responsible Arthropodsmade up the remainder of the diet. for the disappearanceor replacementof fruits at cache The birds foraged singly or in small groups, sitesat a given bower. with females and immature birds overlapping To see whether males would detect and use offered extensively in use of space and fruiting trees fruits, two experimentalsites were establishedat each with males. Males did not defend food re- of the three study bowers; one site was within 1 m and the other from 5 to 10 m from the bower. Fruits sources.Analysis of fecal samples showed at of the same speciesthe male stored were placed at least 130 speciesof fruit utilized by A. macgre- these sitesand their subsequentrecovery monitored goriaeon our study area; individual males ate during normal cachechecks for 7 daysfollowing first fruit from about 30 speciesof trees,shrubs, and placement. Each day, new fruits were placed at emp- vines (Pruett-Jones and Pruett-Jones unpubl. ty sites. data). On 29 November we removed all fruits cached at Dynamicsof fruit caching.--Fruitcaching was the 3 bowers. Once a day for the following 5 days observed only in males and only during the we recorded reestablishment of cache sites, initiation breeding season.Males maintained their bow- of new sites,and ratesof fruit change for thesemales. ers for about 9 months/yr (May-February); Between 23 November and ! December, the entire however, breeding was restricted to Septem- population of active bowers on the study area was checked for cache sites. At each bower we recorded ber-February.From May to August activity was the number of sites found in 30 observer-min of irregular while males rebuilt their bowers. search time and, for each site, the horizontal and ver- During this early phase males did not store tical distance from the bower. All cached fruits were fruit. Caching was observedonly during the collected,and identified if possible. period when males were in regular attendance 336 ?•u•rr-lo•s ^•D P•u•rr-Jo•s [Auk,Vol. 102

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4 8 12 16 20 24 28 32 56 56 2 4 6 8 VERTICAL HEIGHT-m NUMBER OF CACHE SITES 25- Fig. 1. Frequencydistribution of number of cache sitesat 32 complete bowers of adult males (solid line) and 7 rudimentarybowers of immaturemales (dashed line). 15

of their bowersand the majority of intersexual interactions occurred. Late in the season, cach- es were maintained until residents abandoned their bowers.Males remainedin the vicinity of their bower site throughout the year, despite HORIZONTAL DISTANCE-m the markedseasonality of bower attendanceand Fig. 2. Distribution of vertical height and hori- abandonment. Females did not store food, nor zontal distance measurements of 421 cache sites at 31 did they take the food cachedby males. bowers.Vertical height is the distancefrom the cache During 140 h of behavioral observationsin site to the ground. Horizontal distanceis the distance 1982, we saw 20 instancesof caching and re- from the edge of the bower to the cachesite. coveringof fruits by 5 males.Fruit was the only food item cached,and it was gathered after a foraging bout, i.e. it did not appear that males tions. There was a significantand positive cor- went to fruiting treesspecifically to gather the relation between the rank of and the number fruit. Fruit was wedged in or placedat a cache of cachesites at a male'sbower (Spearmanrank site, and when retrieved it was either partially correlation, r = 0.721, P = 0.0001 for all males; or totally consumedor it was moved to a near- r = 0.516, P = 0.0025 for adult males). Males that by site.We observedfruits to be recoveredfrom had the most completebowers, resulting from a site and replaced simultaneously,after a few greateractivity at the site, were alsothe males hours, after several days, or not at all. It was maintaining the most cachesites. our impression that there was considerable Cachingbehavior: population.--We examined 39 variability in the actualstorage and recoveryof bowers, 32 of adult males and 7 of immature individual fruits; however, because our sam- males, for cache sites. A total of 437 was found. pling was limited to twice a day, we were not One (14.2%) immature and 30 (93.8%) adult able to quantify these patternscompletely. males had caches. Adult males had a mean of To examine the relationship between rela- 13.6 (range = 0-55, SD = 12.0) cache sites at tive activity levels of males at bowers and the their bowers,and the single immaturemale had degree of cachingbehavior, we scoredbower 3 (meanfor all immaturemales was 0.4,range = completeness(from I to 5) and comparedthis 0-3, SD = 1.1). The differences between im- with the number of cache sites at each bower. mature and adult males were significant (t = A scoreof 5 representeda completebower with 6.083, P < 0.005).The frequencydistribution of a full maypole and numerous decorationsof cachesites for all malesis shown in Fig. 1. Some different kinds, and a score of 1 indicated an cachesites probably were missedat eachbower incomplete bower structure,lacking a border during the censusbecause of the relativelyshort and base to the maypole and without decora- time spent searching. April 1985] BowerbirdFruit Caching 337

0 20ran I I

Fig. 4. Example of a cachesite in a cavity of a small tree. The fruit is an unidentified drupe.

so that drying could occur, nor were they hid- den from view. 20m The spatial dispersionof 37 cachesites at one of the study bowersis shown in Fig. 5. Scatter- hoarding (Morris 1962) best catagorizes the placement and spacing of stored fruit. Many cache sites, each with one or a few food items, were located within the small core area of each male's home range. Fig. 3. Exampleof a cachesite in a fork of a tree. The fruit is Timoniusspp. (Rubiaceae). Generally, males cachedfresh, ripe fruit, al- though green, unripe fruit occasionally was stored and recovered (presumably eaten) be- fore ripening. Rotten fruits were not cached, Sites were located 0-12.5 m horizontal dis- but fruits sometimes rotted at the cache site be- tance from the bower (mean = 4.0, SD = 1.3, fore being eaten. Such fruits were left at the n = 421 sites at 31 bowers) and 0.2-9.0 m ver- site untouched. tical height from the ground (mean = 2.6, SD = The total number of fruits cached and the 0.8; Fig. 2). Our ability to see sites above 6 m number of fruits at each site varied among was limited, so our sample may be biased to- males. The 31 males with at least 1 cache site wards those near the ground. storeda mean total of 18.3 fruits (range = 1-82, The types of sites used for caching varied SD = 16.8) and an averageof 1.3 fruits (range = among males. The following were encoun- 1-13, SD = 0.5) at each site. Adult males had a tered: fork of tree trunk and branch (Fig. 3), mean total of 17.6 fruits (range = 0-82, SD = point of contact between epiphytic vine and 17.0). Most cachesites chosenby the occupant tree, horizontal branchor large vine, top of tree males could hold only 1 fruit; at 83.6%(352) of stump, fallen log, crown of tree fern, and small the sites,only 1 fruit was found. cavity in tree trunk or branch (Fig. 4). We did The number of speciesof fruit cached by not consider fruits on the ground as cached, malesranged from 1 to 14 and wassignificantly and marked fruits that had fallen to the ground and positively related to the number of cache were not recovered by males. Sites were not sites utilized (Pearson correlation, r = 0.95, P < modified by males,and not all sitespermitted 0.001). A total of 40 species of fruit was col- secureretention of fruit. Dislodgingof fruit by lected from cache sites during the population wind or movement of the site did occur. census.The speciesof fruit stored showed the As the canopyaveraged about 30 m high on range of size and morphology of fruits nor- the study area, cachesites were located in the mally representedin the species'diet. understoryof the forest,well shadedexcept for Cachingbehavior: study bowers.--We moni- diffuse light. Siteswere not exposedto the sun tored a total of 113 sites at 3 study bowers (21 338 PRVETT-JONESANDPRVETT-JONES [Auk,Vol. 102

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•2 8 4 8 12

Fig. 5. Spatialdistribution of cachesites at bower C. The starindicates the positionof the bower;solid circlesrepresent cache sites. Most of thesesites were in smalltrees. The scale(m) is indicated. at bower A, 37 at bower B, and 55 at bower C). were recorded.Fruit shifts occurredonly over Ninety-one of these sites were included in an short distances (<2 m) with no consistent trend analysis of replacement (Table 1). Each male as to the speciesof fruit shifted, directionality made fruit changesat each cachesite an aver- of shift, etc. age of 0.34 times/day. A cachereplacement oc- Of the experimentalsites set up at eachstudy curred on average once every 6-7 days, with a bower, only those sites placed within 1 m of mean of 0.13 replacements.site-•.day-L The the bower were used. As many fruits as were differences among males in rates of site re- offered at the sites (1-4) were removed and placement were not significant (ANOVA, F = presumably eaten, and in 3 instances were 0.06, P = 0.9375) and did not vary with the moved to the males' natural cache sites. number of cache sites (Table 1). Thus, on av- We removed all cached fruit from 104 sites erage, males used each of their cache sites at at the 3 study bowers.At 47 (45%)of thesesites, approximately the same rate, regardlessof the the fruits were eventually replaced. Males re- number of sites. placed the fruit within an average of 2.5 days Extreme differencesin rates of replacement for those siteswhere fruits were cachedagain. existedamong sites. During the 19 daysof sam- Time to replacement was not correlated with pling, the total number of replacements ob- horizontal distance of cache site to bower, with served at individual sites varied from 0 to 14 the rate of cache replacement, or with fruit (mean = 2.5, SD = 2.6, n = 70 sites). One or zero changeat those sites prior to the experiment. fruit changesoccurred at 14 (20%)of thesesites. Mean rates of cache replacement and of fruit Neither rate of cache replacement nor fruit changes at replaced sites were 0.04 and 0.37/ change was correlated with proximity of the day. The rate for site replacement was signifi- siteto the male'sbower. The rate of fruit change cantly lower than the preremoval rate (see at cachesites was greater during the morning above, t = 4.85, P < 0.001). Only 3 new cache hours than in the afternoon. Comparing sites were established by males as a result of changesfrom the previous night's sample to the removal experiment. the noon sampleon a given day with changes from the noon to afternoonsample, cache sites DISCUSSION at bowers B and C had an averagedaily rate of fruit changeof 0.24 during the morning and One explanation for the occurrenceof fruits 0.12 during the afternoon over the 19 days of placed near the males' bowers is that they serve sampling (differences were significant; t = a decorativefunction and possiblyplay a role 4.125, P < 0.001). in intersexual interactions. Males of all bower- At bowers B and C, five instances of fruits building ptilonorhynchids adorn their bowers being shifted from one cache site to another with a wide variety of objects,including fruit April 1985] BowerbirdFruit Caching 339

TABLE1. Comparisonof useof fruit cachesat three studybowers.

Numberof sites Rateof site replacement/day b Rateof fruit change/day b Numberof fruit Bower sampleda Mean SD Mean SD taken/ day• A 15 0.148 0.128 0.336 0.304 2.52 B 30 0.128 0.105 0.306 0.316 4.59 C 46 0.136 0.152 0.376 0.440 8.64 Overall 91 0.135 0.133 0.346 0.381 5.25 aIncludes only those sites at eachbower for whichwe had15 samples. Sites at bowerA weresampled over 8 daysand at bowersB and C, 19 days. bRates were calculatedfor eachsite and averagedover all sitesat eachbower. ½Values represent means for eachmale. Values were calculated by takingthe numberof removalsof fruit at all sitesand dividing by the number of dayssampled.

for mostspecies (Gilllard ! 969, Cooperand For- of fruit to nocturnal marsupials,bats, and ro- shaw 1977, Diamond 1982a). There are, how- dents by dispersingcaches in unrich patches, ever, notable differences in the nature of fruits making it lesseconomical for thesecompetitors used as decorations and fruits stored for food to steal from a cache than to forage for fruit by A. macgregoriae(Table 2). Fruitsused for dec- elsewhere. The distribution of cache sites for orations generally are selectedon the basisof A. macgregoriaealso may be attributed to the color and size, usually are not specieseaten by limitation of suitablesites that can retain larger the bowerbird, and may be used by males in numbersof fruit or to the likelihood that large courtship display. Additionally, decorative piles of fresh fruit may succumbmore rapidly fruits are arranged on the bower itself or with- to molds and bacteria. The absenceof ground- in 1-2 m of the structure, in clear view of vis- or below-ground-levelcache sites also points iting females. In contrast, cached fruits were to the need to protect storedfruit from decom- only of speciesknown to be important in the posers,where, in tropical environments,rot- diet of A. macgregoriae,were scattered incon- ting is accelerated(Roberts !979). spicuouslyin the vegetation,and usuallywere Caching behavior was more common in more than 2 m from the bower. We contend adults than immature males. This is consistent that fruit gathered and stored in the context with the differences between adult and imma- describedin this paper has no function other ture males in bower-building skills, mainte- than as a food source for the male. nance, and attendance. Immature males infre- Although females do not eat or appear to re- quentlybuild bowersand attendthose they do spond to the presenceof the stored fruit, we build on an irregular basis.Caching behavior cannot rule out the possibility that they may probably developsalong with bower-building use the number of cache sites as an assessment behavior. of a male's general foraging ability in their The observedpatterns of use of cache sites choiceof mates.We have not quantified rela- and the dynamicsof cachingbehavior lead us tive mating successof malesin our population, to concludethat fruit cachingin this speciesis a necessaryprerequisite for addressingthis an adaptation within the general context of question. their socialorganization and foraging ecology, MacGregor's Bowerbirds scatter-hoardfruit rather than a primary determinant of spacing within the exclusivedisplay spacearound their and behavior.We suggestthat malesstore food bowers where individuals spend the majority to extend their time at the bower. Cached fruit of their time. Males indirectly protect their may provide sufficientenergy to allow males cache sites from conspecificsby placing them to remain at their bowers longer than other- within the area they aggressively defend. wise possibleand consequentlymay cut down However, no attemptsto take storedfood were the length and/or number of foraging trips. documentedfor rival malesor visiting females. Bowers are essential to males in mating in- Scatter-hoarding often suggests competitive teractions with females; males apparently can- pressurefrom interspecificfruit thieves(Smith not gain matings without an intact, complete and Reichman 1984). Males may reduce loss bower. Additionally, bowersare subjectto rap- 340 PRUETT-JONE$AND PRUETT-JONE$ [Auk, Vol. 102

T^BLE2. Comparisonof characteristicsof fruit cachedfor consumptionby male A. macgregoriaeand fruits usedas decorationsby bowerbirdsgenerally.

Variable Fruits cached Fruits as decorations Source a Nature of fruit Fresh, food species Primarily nonfood species, 1 sometimes dried Proximity to bower 1-14 m from bower On or within 1 m of bower 1 Placement of fruit In vegetationonly, singly On ground, in piles of 10- 1, 3 or in small piles up to 13 100 fruits, or panicles hung in vegetation Preference for color None Strong 1, 2 Occurrenceof stealing None Frequent 1, 4 Consumptionby male Regular Not known 1 Use in courtshipdisplay None May be held in bill by male 1 Sourcesfor information on fruits asdecorations. 1 = Gilllard 1969,Cooper and Forshaw1977, and Diamond 1982a;2 = Schodde1976 and Diamond1982b; 3 = Pruett-Jonesand Pruett-Jones1982; 4 = Borgia1985. id and often frequent destructionby maraud- nonbreeding season,and femalesdo not cache ing males(Pruett-Jones and Pruett-Jones1982). fruit or take the fruit cachedby males to feed Any behavior that would allow malesto spend young. Determining whether the use of cached more time at their bowers (i.e. to be present for fruit increaseslong-term survival of males re- females and to protect the bower against in- quiresfurther study. We have not yet assessed truders) could potentially increase the repro- the males' daily energy requirementsor what ductive successof the male. Considering the fraction of it is met by utilization of cached low rates of female visitation in this species fruit. At bower C, with the greatestnumber of (Pruett-Jonesand Pruett-Jones1982), it is pos- cache sites, the male took an average of 8.6 sible that the primary determinantof mating is fruits/day. While small,this number might po- related to the amount of time a male can spend tentially reduce stressto the male. Addition- in attendance at his bower. Assuming that ally, the male is taking advantageof this num- bower attendanceis constrainedby foraging ber of fruits daily for up to 6 months, a needs, there are relatively few ways a male cumulative effect that might increasesurvival. could extend his attendancetime. He might 1) If the numberof storedfruits eatenby the male make shorter foraging trips or forage only would otherwise be normally consumeddur- within sight of the bower, 2) place his bower ing foraging trips, then the male's total daily near quality foraging areas,or 3) cache fruit. consumptionwould be the same,and survival We do not known the extent to which males probablywould be unaffected.If, on the other attempt the first two options, but given the hand, fruits eaten from cache sites are above temporallyand spatiallyunpredictable fruit re- somebase level eaten by an averagemale, then sourcesthat exist on Mr. Missim (Beehler 1983, survival is likely to be influenced. Pratt 1983), fruit caching may be the only op- It is not known whether other species of tion open to a male. We do not know exactly bowerbirds cache food. Caching has not been when males eat the stored fruit in relation to observed in the most thoroughly studied their foragingtrips or the times femalesor oth- species, the (Ptilonorhynchus er males visit their bowers. However, our find- violaceus),which feeds on a mixed diet of fruit ings show that bower attendanceby malesand and insects(Donaghey 1981). We suspectthat ratesof visitationare greatestduring the morn- other rain forest bower-building ptilonorhyn- ing hours, corresponding to the period of chids will be shown to store fruit. J. Diamond greatestuse of cachedfruit. (pers. comm.) reported food-gatheringbehav- Other speciesin which food storinghas been ior in the forest species,A. inoratus,that may studiedappear to depend more directly on the be indicative of caching. Grassland species stored food for winter survival or for the pro- (Chlamyderaspp.) may be an exceptionbecause visioning of young (Smith and Reichman of the structure of their habitat and varied diets. 1984). This is not the casein MacGregor'sBow- Fruit cachingby bowerbirdsis an area worthy erbird. Males do not cache fruit during the of additional study. April 1985] BowerbirdFruit Caching 341

ACKNOWLEDGMENTS KOENIG,W. D. 1978. Ecologicaland evolutionary aspectsof cooperativebreeding in AcornWood- We wish to thank our field assistant, Simon Stirrat, peckersof central coastalCalifornia. Unpub- who first observedcaching in this species,and our lished Ph.D. dissertation,Berkeley, California, New Guineanassistants Diro, Iling, and Herean,who Univ. of California. helped in a number of ways.This studywas finan- MORRIS,D. 1962. The behaviorof the greenacouchi ciallysupported by the New York ZoologicalSociety, (Myoproctapratti) with specialreference to scat- the FrankM. ChapmanMemorial Fund, a GeorgeD. ter hoarding. J. Zool. 139: 701-732. Harris CareerDevelopment Grant, and Dr. H. Hoog- NEWTON,I. 1979. Population ecology of raptors. straal. Wau Ecology Institute served as our base of Berkhamsted,England, T. & A.D. Poyser. operations in New Guinea. We wish to thank F. Pi- PIZZEY,G. 1980. A field guide to the birds of Aus- telka and the Museumof VertebrateZoology at the tralia. Princeton,New Jersey,Princeton Univ. University of California, Berkeley, for continuous Press. support of our work, and A. Allison, J. and J. Eltham, PRATT,T.K. 1983. Seed dispersalin a montane for- I. and J. Fraser,C. and D. Harvey-Hall, J. Marshall est in Papua New Guinea. Unpublished Ph.D. and New Guinea GoldfieldsPty. Ltd., A. Safford,H. dissertation,New Brunswick,New Jersey,Rut- Sakulas,and the Violaris family for their assistance gers Univ. in New Guinea. B. Beehler, J. Diamond, R. Mumme, PRUITT-JONES,M. A., & S. G. PRUITT-JoNES. 1982. F. Pitelka, T. Pratt, P. Sherman, D. Snow, D. Tom- Spacing and distribution of bowers in Mac- back,and P. Williams madenumerous helpful com- Gregor'sBowerbird ( Amblyornismacgregoriae). mentson earlier drafts of this paper. This paper is Behav. Ecol. Sociobiol. 11: 25-32. contributionNo. 6 from EcologyResearch Associates. ROBERTS,R.C. 1979. The evolution of avian food- storing behavior. Amer. Natur. 114:418-438. LITERATURE CITED SCrtODDE,R. 1976. Evolutionin the birds-of-para- dise and bowerbirds,a resynthesis.Proc. 16th ]•EEHLER,]•. 1983. Behavioralecology of four species Intern. Ornithol. Congr.: 137-149. of bird of paradise. Unpublished Ph.D. disser- SHERRY,D. F., M. AVERY, & A. STEVENS. 1982. The tation, Princeton, New Jersey,Princeton Univ. spacingof storedfood by Marsh Tits. Z. Tierpsy- BORGIA,G. 1985. Bowerdecorations and matingsuc- chol. 58: 153-162. cess of male Satin Bowerbirds. Anita. Behav. 33: SKUTC•, A.F. 1969. Life histories of Central Amer- 266-271. ican birds, III. Pacific Coast Avifauna No. 35. BOSSEMA,I. 1979. Jaysand oaks:an eco-ethological SMITH,C. C., & O. J. REICHMAN. 1984. The evolution study of symbiosis.Behaviour 70: I-I 17. of food caching by birds and mammals.Ann. COOPER,W. T., • J. M. FORSHAW. 1977. The birds of Rev. Ecol. Syst. 15: 329-351. paradiseand bowerbirds.Sydney, Australia, Col- lins Press. TOMBACK,D.F. 1977. Foragingstrategies of Clark's Nutcracker.Living Bird 16: 123-161. CRAIG,R.B. 1974. An analysisof predationby Log- gerheadShrikes ( Laniusludovicianus gambeli Ridg- TUR•EK,F. J., & L. KELSO.1968. Ecologicalaspects way). Unpublished Ph.D. dissertation, Davis, of food transportationand storagein the Corvi- California, Univ. of California. dae. Commun. Behav. Biol., part A. I: 277-297. DIAMOND,J. M. 1982a. Rediscovery of the Yellow- ULFSTRAND,S. 1976. Feedingniches of somepas- fronted Gardener Bowerbird. Science 216: 431- serinebirds in a southSwedish coniferous plan- 434. tation in winter and summer. Ornis Scandinav- 1982b. Evolution of bowerbirds' bowers: ica 7: 21-27. origins of the aestheticsense. Nature 297: VANDERWALL, S. g., •1:R. P. BALDA. 1981. Ecology 99-102. and evolution of food-storagebehavior in coni- DONAGHEY,R. H. 1981. The ecologyand evolution fer-seed-cachingcorvids. Z. Tierpsychol.56: 217- of bowerbirdmating systems. Unpublished Ph.D. 242. dissertation,Clayton, Victoria, Monash Univ. WALTER,H. 1979. Eleonora'sFalcon. Adaptations to GILLlARD,E.T. 1969. Birds of paradiseand bower- prey and habitatin a socialraptor. Chicago, Univ. birds. London, Weidenfeld & Nicholson. ChicagoPress.