Mercury is a highly toxic and pervasive pollutant that has dramatically increased in the environment as a result of coal combustion, gold mining, cement production, hospital waste incineration, and various other human activities around the globe. Its impacts on birds and other wildlife are not yet fully understood, but a new study published in the journal Environmental Pollution suggests that current levels of mercury contamination in many parts of the world are capable of compromising the ability of birds, and likely other vertebrates, to both conserve and rapidly exert energy when needed.