AdvertisementTo Flirt In Cities, Birds Adjust Their PitchPlay04:49Download AudioDecember 24, 2011Sabri Ben-AchourfacebookEmailNorthern cardinals have higher-pitched songs, but those sounds can get garbled in cities, so they've started to sing a little lower. (AP)
Northern cardinals have higher-pitched songs, but those sounds can get garbled in cities, so they've started to sing a little lower. (AP)