mon ▁migr ate ▁to ▁reproduce ; ▁every ▁year ▁they ▁sw im ▁up stream ▁to ▁mate ▁and ▁then ▁return ▁to ▁the ▁ocean . ▁Tem per ature ▁is ▁a ▁driving ▁factor ▁of ▁migration ▁that ▁is ▁dependent ▁on ▁the ▁time ▁of ▁year . ▁Many ▁species , ▁especially ▁birds , ▁migr ate ▁to ▁war mer ▁locations ▁during ▁the ▁winter ▁to ▁escape ▁poor ▁environmental ▁conditions . ▁ ▁Circ ad ian ▁migration ▁is ▁where ▁birds ▁util ize ▁circ ad ian ▁rh ythm ▁( CR ) ▁to ▁reg ulate ▁migration ▁in ▁both ▁the ▁fall ▁and ▁the ▁spring . ▁In ▁circ ad ian ▁migration ▁clock s ▁of ▁both ▁circ ad ian ▁( d aily ) ▁and ▁circ ann ual ▁( ann ual ) ▁patterns ▁are ▁util ized ▁to ▁determine ▁the ▁birds ’ ▁orientation ▁in ▁both ▁time ▁and ▁space ▁as ▁they ▁migr ate ▁from ▁one ▁destination ▁to ▁the ▁next . ▁This ▁type ▁of ▁migration ▁is ▁advantage ous ▁in ▁birds ▁that ▁during ▁the ▁winter ▁remain ▁close ▁to ▁the ▁equ ator , ▁and ▁also ▁allows ▁the ▁monitoring ▁of ▁the ▁aud itory ▁and ▁spatial ▁memory ▁of ▁the ▁birds ’ ▁brain ▁to ▁remember ▁an ▁optimal ▁site ▁of ▁migration . ▁These ▁birds ▁also ▁have ▁timing ▁mechan isms ▁that ▁provide ▁av ians ▁with ▁the ▁distance ▁required ▁to ▁travel ▁in ▁order ▁to ▁reach ▁their ▁destination . ▁To ▁reg ulate ▁the ▁migration ▁patterns ▁of ▁these ▁birds , ▁the ▁m amm al ian ▁circ ad ian ▁clock ▁is ▁util ized . ▁This ▁clock ▁allows ▁birds ▁to ▁determine ▁when ▁the ▁appropriate ▁time ▁is ▁to ▁migr ate , ▁which ▁location ▁will ▁best ▁help