In the dark ages of the 60s, finding lead pellets in the gizzards of dead waterfowl was felt to be evidence of lead poisoning
https://archive.org/details/ontariofishwildlv5n2onta/page/8/mode/2up

[Linked Image from photos.smugmug.com]

Criteria from the 80s

[Linked Image from photos.smugmug.com]

Abstract from 2017
https://www.jstor.org/stable/90010761

Avian cholera and lead poisoning may co-exist, and it is very likely that lead poisoning may increase lethality from avian cholera and avian botulism
https://pubmed.ncbi.nlm.nih.gov/6887448/