ling ▁go ose ▁into ▁six ▁species ▁and ▁ 2 0 0 ▁sub species . ▁The ▁radical ▁nature ▁of ▁this ▁proposal ▁has ▁prov oked ▁surprise ▁in ▁some ▁qu arters ; ▁Richard ▁B anks ▁of ▁the ▁A OU ▁ur ges ▁ca ution ▁before ▁any ▁of ▁Hans on ' s ▁propos als ▁are ▁accepted . ▁ ▁Description ▁ ▁The ▁black ▁head ▁and ▁neck ▁with ▁a ▁white ▁" ch inst rap " ▁distinguish ▁the ▁Canada ▁go ose ▁from ▁all ▁other ▁go ose ▁species , ▁with ▁the ▁exception ▁of ▁the ▁c ack ling ▁go ose ▁and ▁bar n acle ▁go ose ▁( the ▁latter , ▁however , ▁has ▁a ▁black ▁breast ▁and ▁grey ▁rather ▁than ▁brown ish ▁body ▁pl um age ). ▁ ▁The ▁seven ▁sub species ▁of ▁this ▁bird ▁vary ▁widely ▁in ▁size ▁and ▁pl um age ▁details , ▁but ▁all ▁are ▁recogn izable ▁as ▁Canada ▁ge ese . ▁Some ▁of ▁the ▁smaller ▁races ▁can ▁be ▁hard ▁to ▁distinguish ▁from ▁the ▁c ack ling ▁go ose , ▁which ▁slightly ▁overlap ▁in ▁mass . ▁However , ▁most ▁sub species ▁of ▁the ▁c ack ling ▁go ose ▁( ex clus ive ▁of ▁Richard son ' s ▁c ack ling ▁go ose , ▁B . ▁h . ▁h utch in si i ) ▁are ▁consider ably ▁smaller . ▁The ▁smallest ▁c ack ling ▁go ose , ▁B . ▁h . ▁min ima , ▁is ▁scarcely ▁larger ▁than ▁a ▁m all ard . ▁In ▁addition ▁to ▁the ▁size ▁difference , ▁c ack ling ▁ge ese ▁also ▁have ▁a ▁shorter ▁neck ▁and