Social Nesting Habits of Guira Guira

t72 DAVIS,Social Habits of Guira I.I' AukOct.

SOCIAL NESTING HABITS OF GUIRA GUIRA

BY DAVID E. DAVIS

INTRODUCTION THE life historyof Guira guira wasstudied as part of a seriesof researcheson the socialnesting habits of the Crotophaginae,a subfamily of cuckoos.Guira belongsto a monotypicgenus, whose rangeextends from the mouth of the Amazon,the camposof Brazil, southto BahiaBlanca in Argentina. Davis (1940)gives a briefsum- mary of the Crotophaginaeand of the little which was known of the habitsof Guira. The primaryproblems in this studyare the con- siderationof the developmentof the flockhabit and of the manifesta- tion of territorialism.These two problemsare discussedbriefly in this paper; a correlationwith the other membersof the subfamily is reserved for a future time. The greaterpart of the work wasdone in the provinceof Entre Rios, Argentina, with someobservations at Saladasin Corrientesand at Formosa. Through the kindnessof Mr. C. H. Smyth,whose knowl- edgeof the birdsand eggswas invaluable in my work, I wasable to stay at severalestancias belonging to the Bovril Company. I am greatlyindebted to Messrs.C. H. Smyth,Cecil Holland, R. J. Stir- ling, A. S. Dean, and M. Kelly for their generoushospitality, an art among the Anglo-Argentines. The land in Entre Rios,called 'campo,' is gentlyrolling and,where not clearedfor cultivation, is coveredwith leguminoustrees, spaced at intervalsand having the characteristicmushroom shape and lacy foliageof savannavegetation. In the campothere is no undergrowth but a lush growthof grasses.Through this savannathe investigator may easilywalk for miles,but, unlessthe sun is kept in view, may get lost becausein everydirection the vegetationand topographyare identical. SOCIAL BEHAVIOR Flock behavior.--Likeother membersof the subfamily,the birds habituallylive in flocks,spend the day togetherand sleepat night in the sametree. Shortlyafter dawn they file out fromthe sleeping tree to sun themselvesin preparationfor the day'sactivities. Soon the flock,looking for food,scatters about over a wide area,although in mostinstances the variousmembers are within calling distanceof one another. In the eveningthe birds return singly or in small groupsto the sleepingplace, usually a tall thickly foliagedtree. Fre- Vol.•94o 57] a DAVIS,Social Habits o! Guira 473 quently beforeentering the sleepingtree, even as late as after sunset, the birds collectin one particular tree just outsidethe sleepingplace and then all fly in together,using the rattling call and hoppingabout until settled for the night. Theseflocks, however, are not exclusiveorganizations of fixed com- position. The number of birds composingthe flock varies,as is shownfor exampleby the data on Stirling'sgroup. From the 11th to the 19th of November,1939, the daily count of the birds which sleptin the sleepingtree was as follows: 8, 10,?, 7, 8, 9, 6, 8, 6. These changesin compositionof the flockare not entirelydue to newcomers for sometimescertain birds may sleepout in the woodsas shown by the observationof November29: "Two birdsfeeding in 'campo' abouthalf-way to the windmill. Eventuallyone went to the corral (thesleeping place for thegroup). The otherwas joined by a third from the northwest.They sat around,then flew to the north and werejoined by a fourthbird whichcame from near the corralbut was not the first bird. The three birds sat for a long time and then one went into the corral. The other two slept outside. This ex- plainsthe irregularityin numberssleeping in the pareisotrees." Changesin compositionof the flockcan alsotake placeby the additionof newcomersas shownby the followingobservations, giv- ing the fielddata concerning the appearanceof wanderingstrangers. November9, at dawn, "one bird went directlyfrom the sleepingtree to the southand far over the 'arroyo'to the other side,at leasta mile,non-stop flight." November10: "Three birds out by thewind- mill, flewfrom tree to tree,sometimes together, often separated, ap- parentlylooking for a placeto sleep.One carrieda snake(ten incheslong) all the time. After sunsetthe birdswere still flying from tree to tree. I suspectthat theywere looking for a placeto establishthemselves." December 5: "Two birds of the Golf Course groupignored a stranger which sat in thetop of a treeand called." A furtherpoint concerning the organizationof the flockis that thereis a definitetendency for thebirds to remaintogether in pairs, althoughsince the sexes are indistinguishable in the field, no con- clusionscan be drawn as to the sexes. Thus, on November12, "two wentout of thesleeping tree long before the others and went in a differentdirection (from the others)."November 18: "Two pairs wentout, followed by fourbirds." Laterthat day "I foundtwo birds nearthe highway.They wentabout one-half mile to the westand werejoined by two othersfrom the west. Then the four wenteast for a mile beforestopping." Summarizing these observations, it may DAVIS,Social Habits o! Guira LI' AukOct. be said that the flock is a looselyknit organization,whose members tend to associatein pairs. Territorialism.--It is debatable whether the area occupiedby a flock of Guira may be calleda territory,in the strict meaningof the term. Nevertheless,for the presentthe term 'territory'will be used, not only becauseof supportingevidence from the speciesconcerned but also becauseof the fact that the other membersof the subfamily clearlyare territorial. The territoryof a group may extendover a largearea, in somecases more than onemile in diameter. The exact configurationof the territorydepends on the ecologicalconditions; the typicalterritory possesses a sleeping place, consisting of sometall densetrees, usually around an estancia,and a feedingarea in the typicalcampo. The birdsspread out overthis area, one day in one part and anotherday in anotherpart. The evidencein favor of calling this area a territory consistsof observationson the defenseof the area. Typical but brief chasing of the typedescribed for Crotophagaani (Davis,1940) was seen on two occasions.Thus, on November 19, "several birds chasedtwo or three birdsabout one-half mile out into the campo";and againon December8, I "sawa bird chaseanother away and then go to the quinta(sleeping place)." As further evidence, on November28, "! tried to drivefive of Stirling'sbirds to the Windmillgroup and later tried to drivetwo birdsin that direction. Eachtime the birdscircled overmy headand returned." This observanceof the boundaries indicatesthat a true territoryis maintained.Characteristic defense of territorywas observed on severaloccasions. On December3, "manybirds were sitting and calling all overthe area. Several birds flewback and forth and fromplace to place. Three birdsdrove two birds out to the east and then returned. The fighting was not severeand the chasing short." Also on December22, ! "sawa bird driveanother across the roadand away;then return. The pursuit was serious but not fierce." Althoughthese observations indicate a definite territory for each group,on the other hand several observations showthat these terri- toriesare not as strictly delimited as is thecase in Crotophagaani. Thuson December 3, ! sawone group enter the territory of another groupand spend some time feeding before leaving of theirown volition. On December17, while watchingthe nest of a groupat dawn,! sawa birdfrom another group come down to thenest and sit in the same tree as a bird which owned the nest, without any molestationfrom the ownerof the territory. Furthermoreon several Vol.•94o57] a DAVIS,Social Habits o! Guira 475 occasionsbirds came from a long distanceand mingled with the flock and even slept in the sametree. A reconciliationof theseconflicting observations perhaps can be basedon the fact that the membersof one flockmay simultaneously build more than one nest in the territory. For example,on No- vember 30, two nests were found within 200 meters of each other and certainlywithin the territoryof one group. One of thesenests, containingeggs about one-halfincubated, was owned by a pair of birds. The other nest, containingyoung which left the nest when I climbed the tree, was attendedby about five birds. Of thesefive birds only three were solicitous;one of thesethree drove away another bird although pursuing it for only a short distance. Another case of simultaneousnesting within one territory was observedat the Dixon estancia. One nest, in a palm tree, contained four young about three daysold in addition to one partly incubatedegg. The other nest containedfour cold eggs. From informationprovided by the ownersof the estancia,it is absolutelycertain that this latter nest, whichwas high up in an araucariatree about25 metersfrom the first nest, was built after the palm-tree nest. It is certain that human interference did not cause the desertion of the araucaria nest for both nestswere in a garden where the birds were accustomedto human beingsand even to dogs. AlthoughI sawonly two birds in the area,a few dayspreviously there had beenthree. There is thus no doubt that birds of the samegroup built two nestswhich were co•xistent. A third case of co•xistent nests was encountered at the Dean estancia. Somemembers of a colonyof eighteenbirds built one nest,subsequently deserted, in whicheighteen eggs were laid, while membersof the groupwere incubatingat a nest containing fourteeneggs. In additionto thesecases, both Hudson (Sclater and Hudson,1889) and Daguerre(1924) report that pairs may separate off from the flockto build simultaneously.Hudson describes the historyof a colonywhich broke up intogroups of threeor fourbirds and built an abortivenest in October,dropping many eggs on the ground until January,when the birdsbuilt anotherabortive nest and con- tinuedto drop eggson the ground. At the end of January,two pairseach built a nestand raised a totalof fourteenor fifteenyoung. Daguerrereports that one pair of birdstook over an old Mimusnest, repairedit and, with anotherfemale actingparasitically, laid ten eggs. Later when the nest fell down, the pair built another nest and raised eight young. In thosecases in which a pair separatesfrom the rest of the flock 't76 DAVIS,Social Habits o[ Guira LI' AukOct. to build a nest,it is probablethat the ecologicalconditions largely determinewhether it is possibleto leavethe group. If the group sleepsin the only treesavailable for nesting,then the pair cannot separatefrom the restof the groupbut mustbuild in thesetrees. On the other hand, if there are many suitablenest sites, each pair can have its own nest. Thus it is likely that in many casesthe habitat encouragesthe birds to build a communalnest. Thesecases of simultaneousnesting by pairsor groupsof the same flock reconcile the conflictingobservations concerning the defense of territory. A pair of birdsmay looselydefend the nestlocation from other membersof the group, but, sincein many casesthe defenseis not adequate to drive the other birds away, simultaneousor communal nestingmay result in the territory of a group. Call notes.-The call notesof the speciesare discussedat this time becauseof their socialsignificance. 1. The flight flock-callresembles the samecall of G. ani, but is much weakerin volume. The birds usethe call whenevergoing from one placeto another,thus keeping the group together. 2. The alarm call is a very hoarseand loud rattle, usedfor a general alarm. The head is thrown back, crestraised and the whole body shakeswhen the call is given. 3. The dangercall, given for hawks,is a rapid ti-ti-ti-ti-ti, descend- ing in pitch. 4. The socialcall is a loud descendingseries of four or five harsh notes. At the beginningthe bird throws the head far back so that the bill is verticaland at eachnote lowersthe bill slightlyuntil the bill is again horizontal. This call is used frequentlyby the birds in the early morningand at any time during the day to keep the flock together. When the flock is spreadout over a large area, a lonebird cangive the call and thuslocate the othersby the response. This call, referredto asa 'song'by somewriters, has no analogyamong the callsof C. ani, althoughit resemblesthe whew call in sound. 5. When sitting in trees during the mating behavior, a whine, the exact function of which could not be determined, is used. 6. The true pairing note, usedin pairing and when lookingfor a nest site, is a weak whew repeatedslowly. 7. A note frequentlyused before the alarm rattle is a seriesof klee, klee, klee. This very loud note, uttered infrequently, seemsto be used as an intensification of the alarm. 8. Objectionto intrusion at the nest is registered bya croak,also' used in the manner of an alarm. VoL57'[ DAVIS,Social Habits o! Guira 't77 •94o a

On one occasionI heard a soundwhich resembledthe bubbling of C. major greatly. This was given shortly after the birds had gone to the sleepingtree. In summarizingthese calls it shouldbe noted that no call is clearly a territory-defensecall, comparableto songin passerinebirds, al- thoughthere is somepossibility that no. 4 servesthe purpose. The first four calls listed are useful to the flock and therefore may be considered as flock calls. Pairing behavior.--Asin other membersof the subfamily,the pairing behaviorof Guira is simpleand unostentatious.No courtship performancein the usualsense of the termwas observed. The birds, usuallyin pairs,hop aboutin treessuitable for nesting,uttering the pairingnote, a low sibilantwhew. On severaloccasions one bird flutteredits wings,but immediatelyflew out to feed. What is probably the normalcourtship was observed on December9: "Through- out the day one or two birds were in the trees,whining, hopping about,using the pairingcall and flutteringthe wings." Copulation, apparentlya veryinfrequent act, was never observed. This situation is understandablewhen it is rememberedthat, judging from the fre- quencywith whicheggs are foundon the groundeven where there is no nest,this speciesovulates spontaneously; and furthermoreit is probablethat manybirds require only one fertilizationfor the inseminationof all the eggs (cf. SnowBunting, Tinbergen, 1939). Addingto thesephysiological conditions the fact that copulation certainlyoccurs only in bushytrees, it is not surprisingthat the act is not observed. After pairing,the birdshop aboutthe treeslooking for a nest site. During this searchthey frequently carry a leaf aboutin the bill. As soonas the site hasbeen decided upon the birdsbegin to carryin leavesand sticks to constructthe bulkynest. The process of buildingis haphazardand desultory.Sometimes the birdswill notwork for a dayor two;sometimes only one bird works;sometimes manywork, building the nestin a shorttime. In the buildingand layingsequence outlined above, irregularities are frequent.For example,eggs are frequentlydropped on the ground,sometimes even where there is no nest;eggs are laid in the nestbefore it is finished;the nestmay be desertedbefore it is com- pleted.These irregularities are not dueto the interferencefrom otherbirds in the flockfor they occureven when one pair nestsapart from the colony. Even whenthe nestis built within a largecolony, there is a tendencyfor only one pair to be active. The group at 478 DAVIS,Social Habits o! Guira L1-Auk Oct.

Holland'sestancia, consisting of fifteen birds, showedthis proclivity very dearly. In the nestthere were sevenyoung, almost certainly the productof one female. No more than three birds (identifiedindi- viduallyby their tail-feathers)came to the nestand one of thesecame very seldom. Other birds camewithin a coupleof metersof the nest and uttered the alarm call when disturbed,but never actually took part in the incubationor feeding. At another nest (Golf Course) ownedby a flock of about thirteen birds, in generalonly two birds went to the nest, although others came near.

LIFE HISTORY General characteristics.--Guiraguira, known in Argentina as the pirincho or urraca, is one of the most conspicuousand abundant birds, although the habit of going in groupscauses overestimates of their numbers;for when a group is alarmedand fliesup in unison,a false impressionof the number is obtained. Their loud call notes and habit of feedingin open areasmake the birds conspicuous. In generalappearance the birds are typicallycuculine. The long tail and lethargic movementsare at once diagnostic. The flight is labored and consistsof volplaning for long intervals. When the bird comesout of a tree toward the ground, it setsits wings and sails downward, touching the ground with a slight up-swingand then clumsilyrunning for a few steps,hampered by the tail which con- tinues apparentlyindependently and often causesthe bird to lose its balance. Long flightsare accomplishedwith mucheffort. Several otherbehavior characteristics may be notedat this point. The birds do not follow cattle and do not click the bill as a defense measure. Guira resemblesother Crotophaginaein that the body possessesa disagreeableodor. The birds live in any place where there are somebushy trees for sleepingand nesting. Sincenearly every estancia has some tall trees (eucalyptsand others)the birds tend to congregatein the yards. However,groups are commonlyfound out in the campoand do nest there. It seemslikely that the rangeof the bird hasbeen extended southwardsince the settlementof the pampasfor now there are many treesgrowing around each house, providing a placefor the birds to live. On several occasions the birds were seen in the center of smallvillages (Goya, Santa Elena) perchingon the housesand flyingover the cementstreets. A colonylived in PlazaSan Martin in the centerof BuenosAires. This spedesis not particularlyat- tracted to rivers or streams. Vol.57'] D•,ws,Social Habits oI Guira 't79 •94o a

The birds sufferfrom the cold greatlyand in consequenceare fre- quentlyseen sitting huddled together on coolmornings. The natives report that after a cold night or frost, birds may be found dead on the groundunder the sleepingtree. The wind alsois mostannoying to the birds, driving them on blusterydays to remain in the shelter of thickets and banks. Mutual preeningoccurs sometimes during the day but especially when the birds are sitting togetherin the morningor evening. The food consistsof animal matter almostentirely. Of the stom- achsexamined, none containedseeds or fruit. Grubs, caterpillars and large insectsare the main supplyof food; snakes,lizards and young birds are commonlyeaten. During the nestingseason the adults are reported to destroymany young birds of other species. The birds systematicallysearch through the treesfor nests (Pereyra, 1927). Nest and young.--Thenest is usuallylocated in the fork of a tree, althoughin one casea nestwas found in a densebush about three metersfrom the ground but dose to an overhangingbank; while anothernest was suspended in a thickvine. The nest,generally about five metersfrom the ground,is a bulky affair, composedof sticksand lined with leaves,all broken off from trees. Becausethe birds carry in greenleaves during incubation, the nestalways has a cleangreen lining. However,after the youngare hatched the nestbecomes very filthy with the excrementwhich, not containedin a sac,is ejected toward, but seldomover the edge. The eggis large,greenish blue, spotted and splotched with a white calcareouscovering, which is graduallyrubbed off during incubation. One eggfound was completely covered with chalk,thus re- semblingthe egg of ½.ani. The numberof eggslaid by eachfemale is probablyfive to sevenin conformitywith the othermembers of the subfamily.Table 1 givesthe dataon eggsand young found in 1939-40. In addition to these data, Sclater and Hudson (1889) recordthat a colonyof birdsbuilt two nestsand raisedfourteen or fifteenyoung altogether. Gibson (1880) found a nestwith four eggs,and Hartert and Venturi (1909) record nests with 5, 7, 11,19, and21 eggs, and further state that the clutch is five to seven,agreeing with the statementmade by Hudson. Friedmann(1927) found an emptynest and a nestwith six eggs. Since so many eggs are dropped on the groundit is not surprisingthat manynests do not havethe full complement. In the care of the nest the adults are very indolent, sometimes 480 DAVIS,Social Habits o[ Guira L[' Auk oct. leavingthe nestuncovered for the night even though it containseggs or young. Further, it seemsa miraclethat the youngcan growwith- out morefrequent feeding. During a five-hourperiod a nestcontain- ing four young birds three days old was visited by the adults only four times with food. At another nest containing six young birds two daysold, the adults broughtfood only six times in one hour.

TABLE 1

NESTS FOUND 1939--40

Colony Date found Eggs Young Adults Holland ...... Nov. 19 1 6 (2 days old) 15 Williams .... Nov. 24 abortive 4-8 Golf Course .... Nov. 27 I (addled) 1 13 Campo No. 1... Nov. 28 1 (on ground) 4 3+? Stirling ...... Nov. 29 7 (destroyedlater) 7 C.ampo No. 2... Nov. 30 6 (destroyedlater) 2 Dixon No. 1 .... Dee. 12 1 4 (3 days old) 2 Dixon No. 2 .... Dee. 13 4 (deserted) ? Dee. 14 5 4 4 Dean No. I... Jan. 4 14 0 18 Dean No. 2... Jan. 5 11 (deserted) 187 Kelley ...... Jan. 14 7 8 ?

This lackadaisicalcare of the nestmay be an important factor in the developmentof socialnesting. The juvenile birds remain with the flock for severalmonths and soonadopt the adult behavior. The juvenile can be distinguished from the adult by the gray insteadof yellow-and-orangebill which possessesa black rim on the upperside. The iris is blackinstead of orangeas in the adult and the tail-feathersare not frayed. The low crest on the beak soon reaches the adult dimensions.

DISCUSSION This discussionis intendedto bring out someof the moreimportant pointsin the socialhabits of Guira. A correlationwith the behavior of the other membersof the subfamilyis reservedfor a future time. The territorialismof Guira is clearlyin a stateof transition. Each pair maybuild a nestand evendefend the areaaround the nestin a desultorymanner. Yet at the sametime the wholegroup of birds seemsto owna pieceof landand to defendthis land against intrusion. But in all casesthe defenseis falteringand irresolute. Clearly the developmentof territorialismis passingthrough a criticalstage. It shouldfurther be noticedthat there is no fightingin relation to the Vol.194o57] .• DAvis,Social Habits o] Guira 481 sex partner. At no time was any fightingin relation to the female or male seen,a fact which indicatesthat the territorial fighting is purely in relation to a piece of land. Flock organization.--Guiracan be considereda speciesin which the flock sleepsand foragestogether but the pairs nestseparately, a behavior not uncommon in other birds. To indicatethe extentof thesehabits in otherspecies the following noteson the flycatcherMuscivora tyrannus are appended. In Ar- gentina this speciesis migratory;by Novemberat SantaElena (Entre Rios) the birdshave begun to settledown in pairsalthough flocks of 20 to 30 birds are still passingthrough to the regionsfarther south. The first nestsare built in the latter part of November. During the day the birds are spreadout over the campoin pairs and zealously defend their nestsand territoriesfrom any intruder, demonstrating typicalterritorialism. But at duskthe birdsbegin to congregatein the tall bushytrees around the estancias,the favoritesleeping places. The birdsbegin to enterabout sundown, continuing as long as there is light. In the morning they leave before sunriseand go directly to their nests. In one yard, lessthan two acresin extent, about 375 birds,probably including some non-breeding birds, came to roostat the heightof the breedingseason. One bird of eachpair remains on the nestand the other (male?)sleeps in the treeswith othersof the species.From considerationsof the densityof the population of theseflycatchers in the campo,it wasestimated that the birdsmay comefrom a distanceof a mile in radius,an areaof coursedepending on the number of roostingsites available. In summarywe can say that Muscivoratyrannus is a strictlyterritorial species which roosts in largegroups, even in the breedingseason. As anotherexample, the habitsof the Cowbirdsmay be mentioned. The twoparasitic species, Molothrus bonariensis and M. rufoaxillaris, spendthe dayin smallgroups and at nightsleep in vastnumbers in the roostingtrees. The non-parasiticspecies, Agelaioides badius, doesnot roostwith the otherstill after the breedingseason. It is of coursenot surprisingthat a parasiticspecies, which has no nestor territory,should sleep in groupsduring the breedingseason. Theseexamples of birdswhich leave their territoriesor feeding areasto roosttogether suggest one contributing factor in the origin of the flockhabit. The developmentof the flockhabit is in some measuredependent upon the plantcommunities. Before Argentina wassettled, the land waseither pampa (tall-grassprairie) or a type of savannawith treesevenly spacedand characterizedby thin lacy '•82 D.•vIs,Social Habits o[ Guira ['Auk L Oct.

foliage. In theseareas there is evidencethat Guira was either absent or at leastnot commonbefore settlement, and that the specieshas spreadsouthward from the Chaco (Sclater and Hudson, 1889). The Chacois an areaof grasslandinterspersed with numerous'islands' of trees(parkland), an idealplace for the developmentof thisflock- ing habit. The rangeof Guiraextends up into the partlyforested regionsof Brazilwhere Snethlage (1928) found this species only in secondaryforest, savannas,forest islands and similar areas. To summarizethese speculations, it seems likely that the plantcommunities were conducive to the formation of flocks. In addition to the flock habit should be considered the relation of the irregularlaying habits of Guira to the developmentof social nestingand parasitism.As do other membersof the subfamily, Guiradrops eggs at anyplace or at anyphase of the breedingcycle. Eggsmay be found underthe nest,in a half-completednest, or even on the groundfar awayfrom the nest. Furthermore,Guira laysits eggsin the nestof other birds (Milvago,Phytotoma) according to Serie (1923a). Mr. Smythdescribed to me the nestof the Milvagoin whichhe foundtwo Guiraeggs. It wasplaced in a low densegorse hedge,a mostlikely placefor a Guira to be. Phytotomabuilds a nest similar to that of Guira. In addition to these observations is the statementof Azara (1805),doubted by Hudson,that C. ani and Guira lay their eggsin the samenest at times. But much of Azara's information came second-hand from the Indians and furthermore, Guira at times lays eggscompletely covered with white chalk, thus indistinguishablefrom the eggsof C. ani. The above evidenceof promiscuousegg-laying shows that Guira ovulatesspontaneously, or perhapsin responseto a visualstimulus, further increasingthe chance of laying in another bird's nest. In support of this assumption, Farley (1924)reports that a pet bird laid eggsin his houseanywhere and anytime. In summary,it is suggestedthat the neuro-endocrine conditionswhich result in spontaneousovulation permit the developmentof parasitismin the Cuculidae and, in the social Croto- phaginae,permit the developmentof communalnesting instead of colonialnesting as wasdeveloped in the Weaver Finchesand in the parrot Myiopsitta.

SUMMARY 1. As a part of a seriesof researcheson the Crotophaginae,the socialnesting habits of Guira guira, a communallynesting cuckoo, were studied. Vol.•94o57'[ .s DAVIS,Social Habits of Guira zt83

2. This specieslives in looselyorganized flocks, consisting of a varyingnumber of birdswhich spendthe day togetherand sleepin the sametree at night. Within the flock there is a tendencyfor the birds to remain in pairs. 3. Evidenceindicates that the flock maintainsa territory although pairs,which nestsimultaneously even when they belongto the same flock,may maintaina territory. In three casespairs from the same flock built nestssimultaneously, while in four casesthe flock built a communal nest. 4. The speciesuses eight distinctcall notes,all possessingsocial significance. 5. For pairing, the birds merely come togetherand soon hop about the trees 'whining' and looking for a nestingsite. 6. The birds are abundant and conspicuousand typically cu- culine in behavior. They live about habitationsand suffer much from the cold. Their food consistsof animal matter entirely. 7. The nestis a bulkyaffair of sticks,placed in a treeand contains up to twentyeggs, depending upon the number of birdslaying. The normal clutch is five to seveneggs. The adults are indolent in their attentions to the nest. 8. In the discussionof the speciesit is suggestedthat the territorialism is in a stateof transitionand that, as in the casesof other species (Muscivoraand Molothrus)the flockhabit wasencouraged by the ecologicalconditions. Further, the neuro-endocrine conditions which resultin spontaneousovulation, permit the developmentof communalnesting within the flock.

•ILFEREN CES Az•v•, FELIX DE 1805. Apuntamientospara la historianatural de losPaxaros de1 Paraguay y Rio de la Plata. Madrid, 2: 335-352.

DAcv•.va•,Jv• B. 1924. Apuntossobre algunas aves de la provinciade BuenosAires. E1Hornero, 3: 248-252.

1940. Socialnesting habits of the Smooth-billedAni. Auk, 57: 179-218. FARLEY,j. A. 1924. Argentinebirds. Auk, 41: 169-170.

FRIEDMANN, HERBERT 1927. Noteson someArgentina birds. Bull. Mus. Comp.Zoo1., 68: 137-236. z•Sz• DAvis,Social Habits o[Guira [ AukOct.

GIBSON•F-RNEST 1880. Ornithologicalnotes from the neighborhoodof Cape San Antonio, Buenos Ayres. Ibis, (4) 4: 8-11.

HARTERT•'F.., AND VENTURI, $. 1909. Notes sur les oiseauxde la Republique Argentine. NovRatesZool., 16: 159-267.

PEREYRA•CECELIA B. DE 1927. Alimentaci6nde la urracao plrlncho. E1 Hornero, 4: 76.

SCLA•R, W. L., AND HUmON, W. H. 1889. Argentineornithology. London,2: 32-35.

SERIE, PEDRO 1923. Un huevo de pirincho Guira guira en un nido de Phytotoma rutila. E1 Hornero, 3: 100. 1923a.Huevos de pirincho en nido de chimango. E1 Hornero, 3: 189..

SNETHLAGE,HEINRICH 1928. Meine Reise dutch Nordostbrasilien:Biologische Beobachtungen. Journ. f. Ornith., 76: 503-581.

TINBERGEN, N. 1939. The behaviorof the SnowBunting in spring. Trans. Linn. Soc.Ncw York, 5: 1-94.

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