Passengerpigeons(旅鸽)onceflewovermuchoftheUnitedStatesinunbelievablenumbers.Writtenaccountsfromthe18thand19thcenturiesdescribedflocks(群)solargethattheydarkenedtheskyforhours. Itwascalculatedthatwhenitspopulationreachitshighestpoint,thereweremorethan3billionpassengerpigeons–anumberequalto24to40percentofthetotalbirdpopulationintheUnitedStates,makingitperhapsthemostabundantbirdsintheworld.Evenaslateas1870whentheirnumbershadalreadybecomesmaller,aflockbelievedtobe1milewideand320miles(about515kilometers)longwasseennearCincinnati. Sadly,theabundanceofpassengerpigeonsmayhavebeentheirundoing.Wherethebirdswereabundant,peoplebelievedtherewasanever-lastingsupplyandkilledthembythethousands.Commercialhuntersattractedthemtosmallclearingswithgrain,waiteduntilpigeonshadsettledtofeed,thenthrewlargenetsoverthem,takinghundredsatatime.Thebirdswereshippedtolargecitiesandsoldinrestaurants. Bytheclosingdecadesofthe19thcentury,thehardwoodforestswherepassengerpigeonsnestedhadbeendamagedbyAmericans’needforwood,whichscattered(驱散)theflocksandforcedthebirdstogofarthernorth,wherecoldtemperaturesandspringstormscontributedtotheirdecline.Soonthegreatflocksweregone,nevertobeseenagain. In1897,thestateofMichiganpassedalawprohibitingthekillingofpassengerpigeons,butbythen,nosizableflockshadbeenseeninthestatefor10years.ThelastconfirmedwildpigeonintheUnitedStateswasshotbyaboyinPikeCounty,Ohio,in1900.Foratime,afewbirdssurvivedunderhumancare.Thelastofthem,knownaffectionatelyasMartha,diedattheCincinnatiZoologicalGardeninSeptember1,1914. 小题1:Inthe18thandearly19thcenturies,passengerpigeons_______. |