Bird migration is one of nature's great wonders. Here's how ...

Which birds migrate? ... Roughly half of the world's nearly 10,000 known bird species migrate, including several songbirds and seabirds, waterfowl ... SkiptocontentRenewSubscribeMenuSnowgeesetaketotheskiesinOregon'sKlamathBasinNationalWildlifeRefuge.PhotographbyDesignPicsInc,NATGEOIMAGECOLLECTIONPleaseberespectfulofcopyright.Unauthorizeduseisprohibited.Everyspringandfall,aspectacleunfoldsinthenightskyasmillionsofbirdsattemptlong,perilousjourneysbetweentheirsummerbreedingandwinteringgrounds.Mostofthethousandsofbirdspeciesthatengageinthisannualmigrationtravelatnight,whenwindcurrentsaresmootherandthemoonandstarsguidetheirway.Thebirdstypicallyfollowestablishedflyways,generallynorth-southroutesthatofferthebestopportunitiesforrestandrefuelingalongtheway. Multiplebirdspeciessharetheseflightpathsastheycontendwithroughweather,dehydration,starvation,andthethreatofpredation.(Readmoreaboutthelegendarytreksofmigratorybirds.)Arcticterns,forinstance,undertakepole-to-poleroundtripsspanningmorethan60,000miles—arecord,believedtobe theworld’slongestmigrationofanyanimal.Othermigrationsinvolvebirdsflyingeast-westorupanddownmountains.Evenflightlessbirdsmigrate,suchastheAdéliepenguin,whichmakesanearly8,000-miletrekthroughfrigidAntarctica.Becausemigrationissuchanintegralpartoftheavianlifecycle,itwaslikelyalmostasprevalentthousandsofyearsagoasitistoday,saysMartinWikelski,directoroftheMaxPlanckInstituteforOrnithologyandaNationalGeographicExplorer.Pleaseberespectfulofcopyright.Unauthorizeduseisprohibited.Whysomebirdsmigrateandothersdon’tisthefocusofacomplexandactivefieldofresearch.Findingfoodgenerallyisbelievedtobethemaindriver.Additionalmotivationscouldincludetoescapefrominclementweatherandtoreduceexposuretopredatorsorparasites,especiallyduringbreedingseason.Newtechnologicaladvances,suchassophisticatedGPStagsandradar-detectionsystems,aregivingscientistsunprecedentedopportunitiestoobservebirdmigration.AspartofhisICARUSproject,forinstance,WikelskihasoutfittedsomebirdswithFitbit-likedevicesthattracktheirmovementsandtheenvironmentalconditionstheyencounter.Theseminiaturesolar-poweredsatellitetransmitterscouldonedayrevealanimalmigrationsandbehaviorataglobalscalefromspace. “There’sjustsomuchtolearn,”Wikelskisays.“I’vebeentrackingbirdsforovertwodecades,andtheeasewithwhichbirdsseamlesslymigratebetweenworldsisabsolutelyastounding.”Whichbirdsmigrate?Roughlyhalfoftheworld’snearly10,000knownbirdspeciesmigrate,includingseveralsongbirdsandseabirds,waterfowlandwaders,aswellassomeraptors.TheNorthernHemispherehasthemostdiversearrayofmigratorybirds.AmongthemostwellknownareArctic-breedingbar-tailedgodwits,championsofendurance.In2020,scientistsrecordedagodwitundertakingthelongest-knownnonstopmigratoryflightbetweenAlaskaandNewZealand,travelingmorethan7,500milesacrossthePacificOceanfor11daysstraight.(Learnwhybirdsmatter,andareworthprotecting.)Therearealsofeatheredmigrantsthatflyfarandfast.Thegreatsnipe,forinstance,coversdistancesexceeding4,200milesandreachesspeedsofupto60milesperhourwhentravelingnonstopbetweenEuropeandsub-SaharanAfrica,makingitthefastestflyingmigratorybird.Eventinybirdsembarkongargantuanjourneys. Calliopehummingbirds—NorthAmerica’ssmallestbird—make5,600-mileroundtripsbetweenthehigh-elevationmeadowsandopenforestsofthenorthernRockiesandthepine-oakforestsofMexico.Mostspeciesofmigratorybirdsmaybepartialmigrants,meaningthatsomepopulationsorindividualswithinthespeciesmigratewhileothersstayput.AfractionofAmericanrobins,forexample,remainneartheirbreedinggroundsacrossseasonswhileotherstravelsouthandthenreturnnorth.Yellow-eyedjuncosbreedingathighelevationsalongsoutheasternArizona’smountainsaremostlikelytomigrateuptoamiledownslopeduringseveresnowywinters,comparedtothoseatlowerelevationsfacingfewerfoodconstraints.Eventropicalbirds,especiallyinsectivores,undertakeshort-distanceelevationaltrips.Howdotheyknowwheretogo? Inadditiontofollowingcelestialcues,suchasthepositionofthesun,stars,andthemoon,adultbirdsuseamagneticcompasstonavigate.Evenwhentherearenolandmarks,thisinternal“GPSsystem”canpreventthemfromgettinglost.Suchnavigationalacumencanenableindividualbirdstomovethroughregionsnottypicallytraveled.Inexperiments,whensolo-flyingcommoncuckoosweretransportednearly1,500milesawayfromtheirbreedinggroundspriortomigration,theyoftensteeredbacktotheirnormalmigratoryroutes.Butwhataboutinexperiencedbirdsmigratingforthefirsttime?Inoneexperiment,geographicallydisplacedyoungcommoncuckoosnavigatedbacktoroughlythesameflightpathusedbythosebirdsthatweren'tdisplacedfromtheirhome. (Readaboutamazinganimalnavigators.)2:49MeetthemanwhoflieswithmigratingbirdsWhetherthisnavigationalcapacityisinheritedandinnateorlearnedisanongoingdebate.“Ithinkit’sacombinationofinnatetendency,butyoulearnfromothersontheway,”saysWikelski,whohasbeentrackingcommoncuckoossince2012.Onewaytolearnmightbetuningintonocturnalflightcallsfromothermigratingbirds.Distinctfromabirdspecies’regularvocalizations,theseacousticsignalscouldespeciallyguidetheinexperienced,sometimeseventhoseofotherspecies,Wikelskisays.Howdotheyknowit’stimetogo? Forsomebirds,changesinenvironmentalconditions,suchasthelengthoftheday,maytriggermigrationbystimulatinghormones,tellingthebirdsit’stimetofly.Birds’internalbiologicalclockscanalsodetectwhenaseasonshifts,usingcuessuchaschangesinlightandpossiblyairtemperature.Oncethebirdsareinmigrationmode,afeedingfrenzyensues.Thisallowsthebirdstoaccumulatefattopowertheirjourneys,saysLucyHawkes,amigrationscientistattheU.K.’sUniversityofExeterwhocurrentlytracksArcticterns.“Somehow,[thebirds]knowthattheyhavetomigratesoonandgetmassive,”Hawkessays.Localandregionalweatherconditions,suchasrain,wind,andairtemperaturescanalsoinfluencedecisionsaboutwhenmigratorybirdstaketotheskies.Migratinginachangingworld Overall,migrationschedulesseemtobeshifting,asaresultofclimatechange.“Itlookslikebirdmigrationsarecommencingalittleearlierinthespring,”says KyleHorton,anaeroecologistattheUniversityofColoradowhousesradartechnologytomaprealtimeandhistoricalbirdmigrationsintheUnitedStates.Black-throatedbluewarblers,forexample,aremigratingalmostfivedaysearliernow,onaverage,thantheydidinthe1960s.Canada-boundAmericanrobinsarearriving12daysearlierinthespringthantheydidin1994.Migratingwhoopingcranesareshowingupnearly22daysearlierattheirstopoversiteinNebraskainthespringandleavingalmost21dayslaterinthefallthantheydidinthe1940s.(Learnhowclimatechangehasaffectedtheannualmigrationoftheyellowwarbler.)Suchearlystartstomigrationmaybenefitbirdsifplantandinsectproductivityatthebreedinggroundsmirrorthetrend.However,notallmigratorybirdsmaybeabletoadapttoawarmingworld,andiftheydid,thefullcostsofdoingsoremainunclear.Asscientistscontinuetounravelthemysteriesofbirdmigration,thephenomenonremainsoneofnature’sgreatwonders. “They’reflyingallnight,feedingallday,anddoingitagain,”Hortonsays.“That’ssortofremarkable."ShareTweetEmailReadThisNextTheresilienceofthehumanspiritcapturedin29stunningimagesHistory&Culture2021inReviewTheresilienceofthehumanspiritcapturedin29stunningimages2021wasatumultuousyear—butNationalGeographicphotographersstilldocumentedmomentsofperseverance.ReasthewhippetnamedAmerica’sfastestdogAnimalsDomesticatedReasthewhippetnamedAmerica’sfastestdogThethree-year-oldmalerana100-yarddashmorethanhalfasecondfasterthanthe2020winner,amixed-breedrescuedognamedPhelan.ThesefrescoesshatteredconventionsinItalianartTravelWorldHeritageThesefrescoesshatteredconventionsinItalianartInPadua,Giotto’smasterpiecetellsastorycentraltotheChristmasseason.TheuniverseisexpandingfasterthanitshouldbeScienceTheuniverseisexpandingfasterthanitshouldbeThelatestmeasurementswiththeHubbleSpaceTelescopesuggesttheuniverseisexpandingfasterthanscientists'modelspredict—ahintthatsomeunknowningredientcouldbeatworkinthecosmos.GoFurtherAnimalsTigerKingzooownernowbannedfromexhibitinganimals—forlifeAnimalsWildlifeWatchTigerKingzooownernowbannedfromexhibitinganimals—forlifeNewmegadamsthreatenworld’sbiggestfishAnimalsNewmegadamsthreatenworld’sbiggestfishTheseghostlyseacreaturesmakesnowglowintheArcticAnimalsTheseghostlyseacreaturesmakesnowglowintheArcticReasthewhippetnamedAmerica’sfastestdogAnimalsDomesticatedReasthewhippetnamedAmerica’sfastestdogFirsttruemillipedefoundwitharecord-breaking1,306legsAnimalsFirsttruemillipedefoundwitharecord-breaking1,306legsPuffinshavereturnedtotheGulfofMaine—butforhowlong?AnimalsPuffinshavereturnedtotheGulfofMaine—butforhowlong?EnvironmentCouldcrushedrocksabsorbenoughcarbontocurbglobalwarming?EnvironmentPlanetPossibleCouldcrushedrocksabsorbenoughcarbontocurbglobalwarming?Cultivatingtheworld’slargest,stinkiestflowerisnosmalltaskEnvironmentPlanetPossibleCultivatingtheworld’slargest,stinkiestflowerisnosmalltaskCostaRica’spristine‘SharkIsland’nowamassivemarinereserveEnvironmentPlanetPossibleCostaRica’spristine‘SharkIsland’nowamassivemarinereserveThesenationalforestsletyoucutyourownChristmastreeEnvironmentThesenationalforestsletyoucutyourownChristmastreeWhythelinkbetweenclimatechangeandtornadoesiscomplicatedEnvironmentWhythelinkbetweenclimatechangeandtornadoesiscomplicatedHowtofightaninvasiveAmericanbugwithabadderRussianoneEnvironmentPlanetPossibleHowtofightaninvasiveAmericanbugwithabadderRussianoneHistory&CultureThenewyearoncestartedinMarch—here'swhyHistory&CultureThenewyearoncestartedinMarch—here'swhyAmerica’slastslaveshipismoreintactthananyonethoughtHistory&CultureAmerica’slastslaveshipismoreintactthananyonethoughtThis‘cultureofintroverts’preferstohaveconversationsinsongHistory&CultureOutofEdenWalkThis‘cultureofintroverts’preferstohaveconversationsinsongStreamingSanta?HowMr.andMrs.ClausarekeepingupwiththetimesHistory&CultureStreamingSanta?HowMr.andMrs.ClausarekeepingupwiththetimesBiblicalstoriesofJesus'birthrevealcluesabouthistimesHistoryMagazineBiblicalstoriesofJesus'birthrevealcluesabouthistimesEarliestmodernfemalehumaninfantburialfoundinEuropeHistory&CultureEarliestmodernfemalehumaninfantburialfoundinEuropeScienceFDAauthorizesMerck’sCOVID-19antiviralpillScienceCoronavirusCoverageFDAauthorizesMerck’sCOVID-19antiviralpill5thingstoknowaboutCOVID-19testsintheageofOmicronScienceCoronavirusCoverage5thingstoknowaboutCOVID-19testsintheageofOmicronTheworld'smostpowerfulspacetelescopeisreadytolaunchScienceTheworld'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