green ▁she en , ▁while ▁the ▁under parts ▁have ▁a ▁more ▁green ish ▁t int ▁to ▁the ▁black . ▁The ▁eyes ▁are ▁dark ▁brown . ▁The ▁differences ▁are ▁often ▁only ▁really ▁apparent ▁between ▁the ▁two ▁species ▁when ▁seen ▁side ▁by ▁side ▁or ▁when ▁heard ▁calling . ▁The ▁bill ▁is ▁usually ▁somewhat ▁sl immer ▁than ▁the ▁American ▁crow , ▁but ▁is ▁only ▁readily ▁distinguish able ▁if ▁both ▁species ▁are ▁seen ▁together . ▁ ▁Visual ▁different iation ▁from ▁the ▁American ▁crow ▁is ▁extremely ▁difficult ▁and ▁often ▁in ac cur ate . ▁Non eth eless , ▁differences ▁apart ▁from ▁size ▁do ▁exist . ▁Fish ▁c rows ▁tend ▁to ▁have ▁more ▁sl ender ▁b ills ▁and ▁feet . ▁There ▁may ▁also ▁be ▁a ▁small ▁sharp ▁hook ▁at ▁the ▁end ▁of ▁the ▁upper ▁bill . ▁Fish ▁c rows ▁also ▁appear ▁as ▁if ▁they ▁have ▁shorter ▁legs ▁when ▁walking . ▁More ▁dram atically , ▁when ▁calling , ▁fish ▁c rows ▁tend ▁to ▁h unch ▁and ▁fl uff ▁their ▁thro at ▁fe athers . ▁ ▁The ▁voice ▁is ▁the ▁most ▁out ward ly ▁differ ing ▁characteristic ▁for ▁this ▁species ▁and ▁other ▁American ▁crow ▁species . ▁The ▁call ▁of ▁the ▁fish ▁crow ▁has ▁been ▁described ▁as ▁a ▁nas al ▁" ark - ark - ark " ▁or ▁a ▁begg ing ▁" w aw - w aw ". ▁Bird ers ▁often ▁distinguish ▁the ▁two ▁species ▁( in ▁areas ▁where ▁their ▁range ▁over laps ) ▁with ▁the ▁m nem onic ▁aid ▁" Just ▁ask ▁him ▁if ▁he ▁is ▁an ▁American ▁crow . ▁If