They don't have the sense to shelter from the rain, they huddle together to keep warm and suffocate one another, they peck each others tails until they are tailless and bleeding, they practice flying into fences, hanging themselves from them as their heads go through, they impale themselves on sticks when landing, they endeavour to escape from pens before they've learnt to go up to roost or even fly well and then wonder why everything eats them. Sometimes, they just decide to die for no apparent reason that I can see!