Mercury in Everglade Snail Kites?

From USFWS Endangered Species:

Interersting trivia factoid! Mercury was a common ingredient in the production of felt hats in the 1800s, and because exposure to mercury caused slurred speech, tremors, irritability and other odd behavior, the term “mad as a hatter” was coined. Today, contaminant specialists in Florida are working to research mercury levels found in the feathers of Everglade snail kites and how it might affect nesting success of this #endangered species. (Photo by Garry Tucker, USFWS)