▁no ▁evidence ▁was ▁put ▁forward ▁to ▁ref ute ▁the ▁DNA ▁find ings . ▁Mark ▁Const antine , ▁in ▁The ▁Sound ▁Appro ach ▁to ▁Bird ing , ▁illustrated ▁that ▁there ▁is ▁extensive ▁overlap ▁in ▁song ▁types ▁between ▁species ▁from ▁the ▁two ▁gener a , ▁and ▁that ▁voc ally , ▁no ▁characters ▁existed ▁which ▁enabled ▁species ▁to ▁be ▁sorted ▁into ▁one ▁genus ▁or ▁the ▁other . ▁Kenneth ▁William son ▁and ▁H ador am ▁Sh iri hai , ▁in ▁discuss ing ▁the ▁identification ▁of ▁Hi pp ol ais ▁and ▁Ac ro ce phal us ▁war bl ers ▁str essed ▁the ▁similar ities ▁between ▁species ▁in ▁the ▁two ▁gener a . ▁Col in ▁Brad sh aw , ▁in ▁British ▁Bird s , ▁has ▁written ▁several ▁articles ▁on ▁morph ological ▁similarity ▁between ▁cross - generic ▁species - p airs ▁e . g . ▁eastern ▁ol iv ace ous ▁and ▁B ly th ' s ▁re ed ▁war bl ers ▁( B rad sh aw ▁ 2 0 0 0 ) ▁and ▁p addy field ▁and ▁bo oted ▁war bl ers ▁( e . g . ▁Brad sh aw ▁& ▁Ste ele ▁ 1 9 9 5 , ▁Brad sh aw ▁& ▁Ste ele ▁ 1 9 9 7 , ▁the ▁latter ▁a ▁response ▁to ▁Lars ▁Svens son ' s ▁comments ▁on ▁Brad sh aw ▁& ▁Ste ele ▁ 1 9 9 5 ). ▁ ▁The ▁species ▁are : ▁ ▁Gen us ▁Id una ▁ ▁Th ick - bil led ▁war b ler , ▁Id una ▁a ed on