第17章

类别:其他 作者:Charles Darwin字数:5756更新时间:18/12/21 17:23:57
Theseremarks,Imaybepermittedtoadd,directlybearonthecaseoftheSiberiananimalspreservedinice。Thefirmconvictionofthenecessityofavegetationpossessingacharacteroftropicalluxuriance,tosupportsuchlargeanimals,andtheimpossibilityofreconcilingthiswiththeproximityofperpetualcongelation,wasonechiefcauseoftheseveraltheoriesofsuddenrevolutionsofclimate,andofoverwhelmingcatastrophes,whichwereinventedtoaccountfortheirentombment。Iamfarfromsupposingthattheclimatehasnotchangedsincetheperiodwhenthoseanimalslived,whichnowlieburiedintheice。AtpresentIonlywishtoshow,thatasfaras_quantity_offood_alone_isconcerned,theancientrhinocerosesmighthaveroamedoverthe_steppes_ofcentralSiberia(thenorthernpartsprobablybeingunderwater)evenintheirpresentcondition,aswellasthelivingrhinocerosesandelephantsoverthe_Karros_ofSouthernAfrica。 IwillnowgiveanaccountofthehabitsofsomeofthemoreinterestingbirdswhicharecommononthewildplainsofNorthernPatagonia:andfirstforthelargest,orSouthAmericanostrich。Theordinaryhabitsoftheostricharefamiliartoeveryone。Theyliveonvegetablematter,suchasrootsandgrass;butatBahiaBlancaIhaverepeatedlyseenthreeorfourcomedownatlowwatertotheextensivemud-bankswhicharethendry,forthesake,astheGauchossay,offeedingonsmallfish。Althoughtheostrichinitshabitsissoshy,wary,andsolitary,andalthoughsofleetinitspace,itiscaughtwithoutmuchdifficultybytheIndianorGauchoarmedwiththebolas。Whenseveralhorsemenappearinasemicircle,itbecomesconfounded,anddoesnotknowwhichwaytoescape。Theygenerallypreferrunningagainstthewind;yetatthefirststarttheyexpandtheirwings,andlikeavesselmakeallsail。OnonefinehotdayIsawseveralostrichesenterabedoftallrushes,wheretheysquattedconcealed,tillquitecloselyapproached。Itisnotgenerallyknownthatostrichesreadilytaketothewater。Mr。KinginformsmethatattheBayofSanBlas,andatPortValdesinPatagonia,hesawthesebirdsswimmingseveraltimesfromislandtoisland。Theyranintothewaterbothwhendrivendowntoapoint,andlikewiseoftheirownaccordwhennotfrightened:thedistancecrossedwasabouttwohundredyards。Whenswimming,verylittleoftheirbodiesappearabovewater;theirnecksareextendedalittleforward,andtheirprogressisslow。OntwooccasionsIsawsomeostrichesswimmingacrosstheSantaCruzriver,whereitscoursewasaboutfourhundredyardswide,andthestreamrapid。CaptainSturt,[11]whendescendingtheMurrumbidgee,inAustralia,sawtwoemusintheactofswimming。 Theinhabitantsofthecountryreadilydistinguish,evenatadistance,thecockbirdfromthehen。Theformerislargeranddarker-coloured,[12]andhasabiggerhead。Theostrich,Ibelievethecock,emitsasingular,deep-toned,hissingnote:whenfirstIheardit,standinginthemidstofsomesand-hillocks,Ithoughtitwasmadebysomewildbeast,foritisasoundthatonecannottellwhenceitcomes,orfromhowfardistant。 WhenwewereatBahiaBlancainthemonthsofSeptemberandOctober,theeggs,inextraordinarynumbers,werefoundalloverthecountry。Theylieeitherscatteredandsingle,inwhichcasetheyareneverhatched,andarecalledbytheSpaniardshuachos;ortheyarecollectedtogetherintoashallowexcavation,whichformsthenest。OutofthefournestswhichIsaw,threecontainedtwenty-twoeggseach,andthefourthtwenty-seven。 Inoneday’shuntingonhorsebacksixty-foureggswerefound;forty-fourofthesewereintwonests,andtheremainingtwenty,scatteredhuachos。 TheGauchosunanimouslyaffirm,andthereisnoreasontodoubttheirstatement,thatthemalebirdalonehatchestheeggs,andforsometimeafterwardsaccompaniestheyoung。Thecockwhenonthenestliesveryclose;Ihavemyselfalmostriddenoverone。Itisassertedthatatsuchtimestheyareoccasionallyfierce,andevendangerous,andthattheyhavebeenknowntoattackamanonhorseback,tryingtokickandleaponhim。Myinformerpointedouttomeanoldman,whomhehadseenmuchterrifiedbyonechasinghim。IobserveinBurchell’stravelsinSouthAfrica,thatheremarks,“Havingkilledamaleostrich,andthefeathersbeingdirty,itwassaidbytheHottentotstobeanestbird。”IunderstandthatthemaleemuintheZoologicalGardenstakeschargeofthenest:thishabit,therefore,iscommontothefamily。 TheGauchosunanimouslyaffirmthatseveralfemaleslayinonenest。 Ihavebeenpositivelytoldthatfourorfivehenbirdshavebeenwatchedtogointhemiddleoftheday,oneaftertheother,tothesamenest。 Imayadd,also,thatitisbelievedinAfrica,thattwoormorefemaleslayinonenest。[13]Althoughthishabitatfirstappearsverystrange,Ithinkthecausemaybeexplainedinasimplemanner。 Thenumberofeggsinthenestvariesfromtwentytoforty,andeventofifty;andaccordingtoAzara,sometimestoseventyoreighty。Now,althoughitismostprobable,fromthenumberofeggsfoundinonedistrictbeingsoextraordinarilygreatinproportiontotheparentbirds,andlikewisefromthestateoftheovariumofthehen,thatshemayinthecourseoftheseasonlayalargenumber,yetthetimerequiredmustbeverylong。 Azarastates,[14]thatafemaleinastateofdomesticationlaidseventeeneggs,eachattheintervalofthreedaysonefromanother。 Ifthehenwasobligedtohatchherowneggs,beforethelastwaslaidthefirstprobablywouldbeaddled;butifeachlaidafeweggsatsuccessiveperiods,indifferentnests,andseveralhens,asisstatedtobethecase,combinedtogether,thentheeggsinonecollectionwouldbenearlyofthesameage。Ifthenumberofeggsinoneofthesenestsis,asIbelieve,notgreateronanaveragethanthenumberlaidbyonefemaleintheseason,thentheremustbeasmanynestsasfemales,andeachcockbirdwillhaveitsfairshareofthelabourofincubation;andthatduringaperiodwhenthefemalesprobablycouldnotsit,fromnothavingfinishedlaying。[15]Ihavebeforementionedthegreatnumbersofhuachos,ordesertedeggs; sothatinoneday’shuntingtwentywerefoundinthisstate。Itappearsoddthatsomanyshouldbewasted。Doesitnotarisefromthedifficultyofseveralfemalesassociatingtogether,andfindingamalereadytoundertaketheofficeofincubation?Itisevidentthattheremustatfirstbesomedegreeofassociationbetweenatleasttwofemales;otherwisetheeggswouldremainscatteredoverthewideplain,atdistancesfartoogreattoallowofthemalecollectingthemintoonenest:someauthorshavebelievedthatthescatteredeggsweredepositedfortheyoungbirdstofeedon。 ThiscanhardlybethecaseinAmerica,becausethehuachos,althoughoftenfoundaddledandputrid,aregenerallywhole。 WhenattheRioNegroinNorthernPatagonia,IrepeatedlyheardtheGauchostalkingofaveryrarebirdwhichtheycalledAvestruzPetise。 Theydescribeditasbeinglessthanthecommonostrich(whichisthereabundant),butwithaveryclosegeneralresemblance。Theysaiditscolourwasdarkandmottled,andthatitslegswereshorter,andfeatheredlowerdownthanthoseofthecommonostrich。Itismoreeasilycaughtbythebolasthantheotherspecies。Thefewinhabitantswhohadseenbothkinds,affirmedtheycoulddistinguishthemapartfromalongdistance。Theeggsofthesmallspeciesappeared,however,moregenerallyknown;anditwasremarked,withsurprise,thattheywereverylittlelessthanthoseoftheRhea,butofaslightlydifferentform,andwithatingeofpaleblue。 ThisspeciesoccursmostrarelyontheplainsborderingtheRioNegro; butaboutadegreeandahalffurthersouththeyaretolerablyabundant。 WhenatPortDesire,inPatagonia(lat。48degs。),Mr。Martensshotanostrich;andIlookedatit,forgettingatthemoment,inthemostunaccountablemanner,thewholesubjectofthePetises,andthoughtitwasanotfull-grownbirdofthecommonsort。Itwascookedandeatenbeforemymemoryreturned。 Fortunatelythehead,neck,legs,wings,manyofthelargerfeathers,andalargepartoftheskin,hadbeenpreserved;andfromtheseaverynearlyperfectspecimenhasbeenputtogether,andisnowexhibitedinthemuseumoftheZoologicalSociety。Mr。Gould,indescribingthisnewspecies,hasdonemethehonourofcallingitaftermyname。 AmongthePatagonianIndiansintheStraitofMagellan,wefoundahalfIndian,whohadlivedsomeyearswiththetribe,buthadbeenborninthenorthernprovinces。IaskedhimifhehadeverheardoftheAvestruzPetise? Heansweredbysaying,“Why,therearenoneothersinthesesoutherncountries。” Heinformedmethatthenumberofeggsinthenestofthepetiseisconsiderablylessthaninthatoftheotherkind,namely,notmorethanfifteenonanaverage,butheassertedthatmorethanonefemaledepositedthem。AtSantaCruzwesawseveralofthesebirds。Theywereexcessivelywary:Ithinktheycouldseeapersonapproachingwhentoofarofftobedistinguishedthemselves。Inascendingtheriverfewwereseen;butinourquietandrapiddescent,many,inpairsandbyfoursorfives,wereobserved。Itwasremarkedthatthisbirddidnotexpanditswings,whenfirststartingatfullspeed,afterthemannerofthenorthernkind。InconclusionImayobserve,thattheStruthiorheainhabitsthecountryofLaPlataasfarasalittlesouthoftheRioNegroinlat。41degs。,andthattheStruthioDarwiniitakesitsplaceinSouthernPatagonia;thepartabouttheRioNegrobeingneutralterritory。M。A。d’Orbigny,[16]whenattheRioNegro,madegreatexertionstoprocurethisbird,butneverhadthegoodfortunetosucceed。Dobrizhoffer[17]longagowasawareoftherebeingtwokindsofostriches,hesays,“Youmustknow,moreover,thatEmusdifferinsizeandhabitsindifferenttractsofland;forthosethatinhabittheplainsofBuenosAyresandTucumanarelarger,andhaveblack,whiteandgreyfeathers;thoseneartotheStraitofMagellanaresmallerandmorebeautiful,fortheirwhitefeathersaretippedwithblackattheextremity,andtheirblackonesinlikemannerterminateinwhite。” Averysingularlittlebird,Tinochorusrumicivorus,isherecommon: initshabitsandgeneralappearance,itnearlyequallypartakesofthecharacters,differentastheyare,ofthequailandsnipe。TheTinochorusisfoundinthewholeofsouthernSouthAmerica,wherevertherearesterileplains,oropendrypastureland。Itfrequentsinpairsorsmallflocksthemostdesolateplaces,wherescarcelyanotherlivingcreaturecanexist。 Uponbeingapproachedtheysquatclose,andthenareverydifficulttobedistinguishedfromtheground。Whenfeedingtheywalkratherslowly,withtheirlegswideapart。Theydustthemselvesinroadsandsandyplaces,andfrequentparticularspots,wheretheymaybefounddayafterday:likepartridges,theytakewinginaflock。Inalltheserespects,inthemusculargizzardadaptedforvegetablefood,inthearchedbeakandfleshynostrils,shortlegsandformoffoot,theTinochorushasacloseaffinitywithquails。 Butassoonasthebirdisseenflying,itswholeappearancechanges;thelongpointedwings,sodifferentfromthoseinthegallinaceousorder,theirregularmannerofflight,andplaintivecryutteredatthemomentofrising,recalltheideaofasnipe。ThesportsmenoftheBeagleunanimouslycalledittheshort-billedsnipe。Tothisgenus,orrathertothefamilyoftheWaders,itsskeletonshowsthatitisreallyrelated。 TheTinochorusiscloselyrelatedtosomeotherSouthAmericanbirds。 TwospeciesofthegenusAttagisareinalmosteveryrespectptarmigansintheirhabits;onelivesinTierradelFuego,abovethelimitsoftheforestland;andtheotherjustbeneaththesnow-lineontheCordilleraofCentralChile。Abirdofanothercloselyalliedgenus,Chionisalba,isaninhabitantoftheantarcticregions;itfeedsonsea-weedandshellsonthetidalrocks。Althoughnotwebfooted,fromsomeunaccountablehabit,itisfrequentlymetwithfaroutatsea。Thissmallfamilyofbirdsisoneofthosewhich,fromitsvariedrelationstootherfamilies,althoughatpresentofferingonlydifficultiestothesystematicnaturalist,ultimatelymayassistinrevealingthegrandscheme,commontothepresentandpastages,onwhichorganizedbeingshavebeencreated。 ThegenusFurnariuscontainsseveralspecies,allsmallbirds,livingontheground,andinhabitingopendrycountries。InstructuretheycannotbecomparedtoanyEuropeanform。Ornithologistshavegenerallyincludedthemamongthecreepers,althoughopposedtothatfamilyineveryhabit。 Thebestknownspeciesisthecommonoven-birdofLaPlata,theCasaraorhousemakeroftheSpaniards。Thenest,whenceittakesitsname,isplacedinthemostexposedsituations,asonthetopofapost,abarerock,oronacactus。Itiscomposedofmudandbitsofstraw,andhasstrongthickwalls:inshapeitpreciselyresemblesanoven,ordepressedbeehive。Theopeningislargeandarched,anddirectlyinfront,withinthenest,thereisapartition,whichreachesnearlytotheroof,thusformingapassageorantechambertothetruenest。