M。Prevostalone，Ithink，hasthrownlightbyhisobservations[9]onthispuzzle：hefindsthatthefemalecuckoo，which，accordingtomostobservers，laysatleastfromfourtosixeggs，mustpairwiththemaleeachtimeafterlayingonlyoneortwoeggs。Now，ifthecuckoowasobligedtositonherowneggs，shewouldeitherhavetositonalltogether，andthereforeleavethosefirstlaidsolong，thattheyprobablywouldbecomeaddled；orshewouldhavetohatchseparatelyeachegg，ortwoeggs，assoonaslaid：butasthecuckoostaysashortertimeinthiscountrythananyothermigratorybird，shecertainlywouldnothavetimeenoughforthesuccessivehatchings。Hencewecanperceiveinthefactofthecuckoopairingseveraltimes，andlayinghereggsatintervals，thecauseofherdepositinghereggsinotherbirds’nests，andleavingthemtothecareoffoster-parents。Iamstronglyinclinedtobelievethatthisviewiscorrect，fromhavingbeenindependentlyledasweshallhereaftersee
　　toananalogousconclusionwithregardtotheSouthAmericanostrich，thefemalesofwhichareparasitical，ifImaysoexpressit，oneachother；
　　eachfemalelayingseveraleggsinthenestsofseveralotherfemales，andthemaleostrichundertakingallthecaresofincubation，likethestrangefoster-parentswiththecuckoo。
　　Iwillmentiononlytwootherbirds，whichareverycommon，andrenderthemselvesprominentfromtheirhabits。TheSaurophagussulphuratusistypicalofthegreatAmericantribeoftyrant-flycatchers。Initsstructureitcloselyapproachesthetrueshrikes，butinitshabitsmaybecomparedtomanybirds。Ihavefrequentlyobservedit，huntingafield，hoveringoveronespotlikeahawk，andthenproceedingontoanother。Whenseenthussuspendedintheair，itmightveryreadilyatashortdistancebemistakenforoneoftheRapaciousorder；itsstoop，however，isveryinferiorinforceandrapiditytothatofahawk。AtothertimestheSaurophagushauntstheneighbourhoodofwater，andthere，likeakingfisher，remainingstationary，itcatchesanysmallfishwhichmaycomenearthemargin。Thesebirdsarenotunfrequentlykepteitherincagesorincourtyards，withtheirwingscut。Theysoonbecometame，andareveryamusingfromtheircunningoddmanners，whichweredescribedtomeasbeingsimilartothoseofthecommonmagpie。Theirflightisundulatory，fortheweightoftheheadandbillappearstoogreatforthebody。IntheeveningtheSaurophagustakesitsstandonabush，oftenbytheroadside，andcontinuallyrepeatswithoutachangeashrillandratheragreeablecry，whichsomewhatresemblesarticulatewords：theSpaniardssayitislikethewords“Bienteveo“
　　Iseeyouwell，andaccordinglyhavegivenitthisname。
　　Amocking-birdMimusorpheus，calledbytheinhabitantsCalandria，isremarkable，frompossessingasongfarsuperiortothatofanyotherbirdinthecountry：indeed，itisnearlytheonlybirdinSouthAmericawhichIhaveobservedtotakeitsstandforthepurposeofsinging。ThesongmaybecomparedtothatoftheSedgewarbler，butismorepowerful；
　　someharshnotesandsomeveryhighones，beingmingledwithapleasantwarbling。Itisheardonlyduringthespring。Atothertimesitscryisharshandfarfromharmonious。NearMaldonadothesebirdsweretameandbold；theyconstantlyattendedthecountryhousesinnumbers，topickthemeatwhichwashunguponthepostsorwalls：ifanyothersmallbirdjoinedthefeast，theCalandriasoonchaseditaway。OnthewideuninhabitedplainsofPatagoniaanothercloselyalliedspecies，O。Patagonicaofd’Orbigny，whichfrequentsthevalleysclothedwithspinybushes，isawilderbird，andhasaslightlydifferenttoneofvoice。Itappearstomeacuriouscircumstance，asshowingthefineshadesofdifferenceinhabits，thatjudgingfromthislatterrespectalone，whenIfirstsawthissecondspecies，IthoughtitwasdifferentfromtheMaldonadokind。Havingafterwardsprocuredaspecimen，andcomparingthetwowithoutparticularcare，theyappearedsoverysimilar，thatIchangedmyopinion；butnowMr。Gouldsaysthattheyarecertainlydistinct；aconclusioninconformitywiththetriflingdifferenceofhabit，ofwhich，ofcourse，hewasnotaware。
　　Thenumber，tameness，anddisgustinghabitsofthecarrion-feedinghawksofSouthAmericamakethempre-eminentlystrikingtoanyoneaccustomedonlytothebirdsofNorthernEurope。InthislistmaybeincludedfourspeciesoftheCaracaraorPolyborus，theTurkeybuzzard，theGallinazo，andtheCondor。TheCaracarasare，fromtheirstructure，placedamongtheeagles：weshallsoonseehowilltheybecomesohigharank。Intheirhabitstheywellsupplytheplaceofourcarrion-crows，magpies，andravens；
　　atribeofbirdswidelydistributedovertherestoftheworld，butentirelyabsentinSouthAmerica。TobeginwiththePolyborusBrasiliensis：thisisacommonbird，andhasawidegeographicalrange；itismostnumerousonthegrassysavannahsofLaPlatawhereitgoesbythenameofCarrancha，andisfarfromunfrequentthroughoutthesterileplainsofPatagonia。
　　InthedesertbetweentheriversNegroandColorado，numbersconstantlyattendthelineofroadtodevourthecarcassesoftheexhaustedanimalswhichchancetoperishfromfatigueandthirst。Althoughthuscommoninthesedryandopencountries，andlikewiseonthearidshoresofthePacific，itisneverthelessfoundinhabitingthedampimperviousforestsofWestPatagoniaandTierradelFuego。TheCarranchas，togetherwiththeChimango，constantlyattendinnumberstheestanciasandslaughtering-houses。IfananimaldiesontheplaintheGallinazocommencesthefeast，andthenthetwospeciesofPolyboruspickthebonesclean。Thesebirds，althoughthuscommonlyfeedingtogether，arefarfrombeingfriends。WhentheCarranchaisquietlyseatedonthebranchofatreeorontheground，theChimangooftencontinuesforalongtimeflyingbackwardsandforwards，upanddown，inasemicircle，tryingeachtimeatthebottomofthecurvetostrikeitslargerrelative。TheCarranchatakeslittlenotice，exceptbybobbingitshead。AlthoughtheCarranchasfrequentlyassembleinnumbers，theyarenotgregarious；forindesertplacestheymaybeseensolitary，ormorecommonlybypairs。
　　TheCarranchasaresaidtobeverycrafty，andtostealgreatnumbersofeggs。Theyattempt，also，togetherwiththeChimango，topickoffthescabsfromthesorebacksofhorsesandmules。Thepooranimal，ontheonehand，withitsearsdownanditsbackarched；and，ontheother，thehoveringbird，eyeingatthedistanceofayardthedisgustingmorsel，formapicture，whichhasbeendescribedbyCaptainHeadwithhisownpeculiarspiritandaccuracy。Thesefalseeaglesmostrarelykillanylivingbirdoranimal；andtheirvulture-like，necrophagoushabitsareveryevidenttoanyonewhohasfallenasleeponthedesolateplainsofPatagonia，forwhenhewakes，hewillsee，oneachsurroundinghillock，oneofthesebirdspatientlywatchinghimwithanevileye：itisafeatureinthelandscapeofthesecountries，whichwillberecognisedbyeveryonewhohaswanderedoverthem。Ifapartyofmengoouthuntingwithdogsandhorses，theywillbeaccompanied，duringtheday，byseveraloftheseattendants。Afterfeeding，theuncoveredcrawprotrudes；atsuchtimes，andindeedgenerally，theCarranchaisaninactive，tame，andcowardlybird。Itsflightisheavyandslow，likethatofanEnglishrook。Itseldomsoars；butIhavetwiceseenoneatagreatheightglidingthroughtheairwithmuchease。Itrunsincontradistinctiontohopping，butnotquitesoquicklyassomeofitscongeners。AttimestheCarranchaisnoisy，butisnotgenerallyso：
　　itscryisloud，veryharshandpeculiar，andmaybelikenedtothesoundoftheSpanishgutturalg，followedbyaroughdoublerr；whenutteringthiscryitelevatesitsheadhigherandhigher，tillatlast，withitsbeakwideopen，thecrownalmosttouchesthelowerpartoftheback。Thisfact，whichhasbeendoubted，isquitetrue；Ihaveseenthemseveraltimeswiththeirheadsbackwardsinacompletelyinvertedposition。TotheseobservationsImayadd，onthehighauthorityofAzara，thattheCarranchafeedsonworms，shells，slugs，grasshoppers，andfrogs；thatitdestroysyounglambsbytearingtheumbilicalcord；andthatitpursuestheGallinazo，tillthatbirdiscompelledtovomitupthecarrionitmayhaverecentlygorged。Lastly，AzarastatesthatseveralCarranchas，fiveorsixtogether，willuniteinchaseoflargebirds，evensuchasherons。Allthesefactsshowthatitisabirdofveryversatilehabitsandconsiderableingenuity。
　　ThePolyborusChimangoisconsiderablysmallerthanthelastspecies。
　　Itistrulyomnivorous，andwilleatevenbread；andIwasassuredthatitmateriallyinjuresthepotatocropsinChiloe，bystockinguptherootswhenfirstplanted。Ofallthecarrion-feedersitisgenerallythelastwhichleavestheskeletonofadeadanimal，andmayoftenbeseenwithintheribsofacoworhorse，likeabirdinacage。AnotherspeciesisthePolyborusNovaeZelandiae，whichisexceedinglycommonintheFalklandIslands。ThesebirdsinmanyrespectsresembleintheirhabitstheCarranchas。
　　Theyliveonthefleshofdeadanimalsandonmarineproductions；andontheRamirezrockstheirwholesustenancemustdependonthesea。Theyareextraordinarilytameandfearless，andhaunttheneighborhoodofhousesforoffal。Ifahuntingpartykillsananimal，anumbersooncollectandpatientlyawait，standingonthegroundonallsides。Aftereating，theiruncoveredcrawsarelargelyprotruded，givingthemadisgustingappearance。
　　Theyreadilyattackwoundedbirds：acormorantinthisstatehavingtakentotheshore，wasimmediatelyseizedonbyseveral，anditsdeathhastenedbytheirblows。TheBeaglewasattheFalklandsonlyduringthesummer，buttheofficersoftheAdventure，whowerethereinthewinter，mentionmanyextraordinaryinstancesoftheboldnessandrapacityofthesebirds。
　　Theyactuallypouncedonadogthatwaslyingfastasleepclosebyoneoftheparty；andthesportsmenhaddifficultyinpreventingthewoundedgeesefrombeingseizedbeforetheireyes。ItissaidthatseveraltogetherinthisrespectresemblingtheCarranchaswaitatthemouthofarabbit-hole，andtogetherseizeontheanimalwhenitcomesout。Theywereconstantlyflyingonboardthevesselwhenintheharbour；anditwasnecessarytokeepagoodlookouttopreventtheleatherbeingtornfromtherigging，andthemeatorgamefromthestern。Thesebirdsareverymischievousandinquisitive；theywillpickupalmostanythingfromtheground；alargeblackglazedhatwascarriednearlyamile，aswasapairoftheheavyballsusedincatchingcattle。Mr。Usborneexperiencedduringthesurveyamoresevereloss，intheirstealingasmallKater’scompassinaredmoroccoleathercase，whichwasneverrecovered。Thesebirdsare，moreover，quarrelsomeandverypassionate；tearingupthegrasswiththeirbillsfromrage。Theyarenottrulygregarious；theydonotsoar，andtheirflightisheavyandclumsy；onthegroundtheyrunextremelyfast，verymuchlikepheasants。Theyarenoisy，utteringseveralharshcries，oneofwhichislikethatoftheEnglishrook，hencethesealersalwayscallthemrooks。
　　Itisacuriouscircumstancethat，whencryingout，theythrowtheirheadsupwardsandbackwards，afterthesamemannerastheCarrancha。Theybuildintherockycliffsofthesea-coast，butonlyonthesmalladjoiningislets，andnotonthetwomainislands：thisisasingularprecautioninsotameandfearlessabird。Thesealerssaythatthefleshofthesebirds，whencooked，isquitewhite，andverygoodeating；butboldmustthemanbewhoattemptssuchameal。