A wren : researchers identified ' urban adapters ' as crows , wrens and tits which all come from the same family and all have larger brains compared to their bodies
He plucks a wren with tweezers ( one of many roadkill samples squirrelled away in his freezer ) , and in order to verify why vultures have evolved with featherless heads ( and long necks ) he dunks feathers into a bowl of dead bullfrogs then blasts them with a hairdryer .