Most birds of prey, such as eagles, hawks, ravens and gulls get lead poisoning through leftover gut piles, un-retrieved carcasses and varmint carcasses left in the field. Birds of prey, also known as Raptors, along with scavengers will ingest lead ammunition fragments left in the tissue of carcasses. They can also ingest lead tackle left behind in fish.
If not treated by professional veterinarians or licensed rehabilitators, these birds will die a slow death. Lead poisoning, depending on the level of toxicity, could take weeks for a bird to succumb to the effects. Symptoms include weakness, emaciation, and un-coordination. They can not fly or even walk. Because of this, these birds are found long roadsides scavenging off of roadkill and are then hit by cars.
Here is a webinar by the PA Game Commission on Lead.