ne ck ed ▁sw an ▁bre eds ▁in ▁Chile an ▁Southern ▁Zone , ▁Pat ag onia , ▁T ierra ▁del ▁Fu ego ▁and ▁on ▁the ▁F alk land ▁Islands . ▁In ▁the ▁austral ▁winter , ▁this ▁species ▁migr ates ▁north wards ▁to ▁Par agu ay , ▁Boliv ia ▁and ▁southern ▁Brazil . ▁The ▁wet lands ▁created ▁by ▁the ▁Great ▁Chile an ▁earth qu ake ▁like ▁Carlos ▁An wand ter ▁Nature ▁San ctu ary ▁in ▁Cru ces ▁River ▁have ▁become ▁important ▁population ▁cent ers ▁for ▁the ▁black - ne ck ed ▁sw an . ▁ ▁Status ▁and ▁conservation ▁In ▁ 2 0 0 4 ▁and ▁ 2 0 0 5 ▁thousands ▁of ▁black - ne ck ed ▁sw ans ▁in ▁the ▁Carlos ▁An wand ter ▁Nature ▁San ctu ary ▁in ▁Chile ▁died ▁or ▁migr ated ▁away ▁following ▁major ▁cont am ination ▁by ▁Val div ia ▁P ulp ▁Mill ▁located ▁on ▁the ▁Cru ces ▁River ▁which ▁fe eds ▁the ▁wet lands . ▁By ▁August ▁ 2 0 0 5 ▁the ▁birds ▁in ▁the ▁San ctu ary ▁had ▁been ▁" w ip ed ▁out "; ▁only ▁four ▁birds ▁could ▁be ▁observed ▁from ▁a ▁population ▁formerly ▁estimated ▁at ▁ 5 0 0 0 ▁birds . ▁Aut ops ies ▁on ▁dead ▁sw ans ▁attributed ▁the ▁death s ▁to ▁high ▁levels ▁of ▁iron ▁and ▁other ▁met als ▁poll uting ▁the ▁water . ▁ ▁W ides p read ▁and ▁common ▁throughout ▁its ▁habitat , ▁the ▁black - ne ck ed ▁sw an ▁is ▁evaluated ▁as ▁Le ast ▁Conc ern ▁on