Lead poisoning in mute swans Cygnus olor in Ireland: a review

Almost 70% of all mute swans examined died from lead poisoning. Two sources of ingested lead resulting in fatalities were identified: spent gunshot and lost or discarded anglers' lead weights. In most cases, lead concentrations in the tissues were highest according to the cause of death in order: lead poisoning > collision > other causes. Over 40% of blood samples from one site showed elevated lead. X-ray examination of live swans revealed the source of contamination to be ingested lead pellets. Urban birds had higher lead levels than rural birds. The blood levels of rural birds were presumed to reflect background levels. -from Authors