.
Birdsincitiesaredamagingtheirhealthbytryingtosingabovethenoiseofurbanlife.
Newresearchshowsthatmalebirdsaretryingtocompeteagainsttrafficandcitysounds.Theyarenowsinginglouderandathigherfrequencies,whichcouldharmtheirvocalcords.Somebirdsarechoosingtosingatnightinsteadofdudngtheday.Thismakesthemmoreopentoattackandalsocreatesstressandexhanstion.
“Thedifferencebetweenurbanandruralbirdsongisbecomingsobigthatthetwogroupscouldnowbeunabletocommunicate.Thiscouldleadtoinbreedingandaweakgenepool.”saidDrSueAnneZollingeroftheUniversityofStAndrews.
AccordingtoZollingarabirdgroupwithasmallgeaepoolmightadaptlessquicklytonewdiseasesandcouldbewipedout.
AstudyofthedawnchorusfoundthatbirdsinBerlinsangupto14decibels(分贝)louderthanthoseintheforest.Thebirdssangloudestonweekdaymomings.
“Bytryingtosingoverthesoundofthecitybirdsarerisingvocalinjury”saidZollinger.“Allthisputsthesarnestrainonabird’svocalcordsaswhen ahumanneedtoshouttobeheard—exceptthebirdsaredoingitalldayeveryday”shesaid.
“Singingundersuchpressuremeansbirdshavelesscontroloverthesoundtheyproduce.Theirsongsmaylosequalityandbecomemorerough—sounding.”saidZollinger.Thiscouldmakethemappearlessattractivetofemalebirds.
MarkConstantine,authorofTheSoundApproachtoBirding,said:“Birdsongisimportantforourqualityoflifeandhasbeenprovedtoreduceourbloodpressure.Whenweliveinthecentreoflarge,urbanareas,wegetstressedandit'sextremelygoodtohavebirdsongaroundus.Theimpactonhumansofbirdsongismassive.Itharmsus,aswellasthebirds,iftheirsongsbecomelouderandsimpler
53.Somebirdsincitiesnowchoosetosingatnighttimebecause_______.
A.theywanttoattractmorebirdsofoppositesex
B.theyaremorelikelytobediscoveredbytheirfamily
C.theycan’tadapttotheloudnoisesduringthedaytime
D.theyhavetofrightentheirenemyaway
54.Accordingtothepassage,urbanandruralbirdsmightnotbeableto_______.
A.recognizeeachother
B communicatewitheachother