 The American Eagle Foundation warns that a lead fragment the size of a grain of rice can be lethal to a bald eagle. The biggest impact we see is certainly from the neurologic effects. When their brains are impaired by lead poisoning, they have a harder time avoiding cars. Federal agencies and outside researchers think ammo is the most likely culprit, but there could be others. Some experts noted cases of poisoning were most common during hunting season. Federal efforts to ban lead ammo have so far failed in Congress.