Over the last 10 years or so, there have been a number of studies that show that migratory birds are returning to Canada’s Arctic to breed in the summer with dangerous cargo.
High levels of toxins, including pesticides, cadmium, mercury and PCBs, are released into the environment in various ways and end up in the world’s oceans. These toxins are taken up by plankton, concentrated in the fish and shellfish that eat the plankton, and concentrated again in birds that eat the fish. With each successive level in the food chain, the amount and concentration of toxins is magnified. Migratory birds return to the Arctic by the thousands, loaded with this poisonous freight.
If you thought that bird poop was unpleasant on its own, consider bird poop laced with toxic compounds. The birds gather in great numbers around Arctic lakes and do what birds do so well: breed and excrete. The toxic bird poop concentrates these poisons in the lakes at levels as much as 60 times greater than are found in nearby lakes with no birds.
Recently published work by researchers at Queens University, University of Ottawa and the Canadian Wildlife Service (doi:10.1016/j.envpol.2010.07.014) has shown that toxins such as PCBs are also found at higher levels on land, in lichens and mosses near the bird colonies. There’s a lot of work still to do in order to understand how far up the terrestrial food chain these toxins go but one thing seems clear: these toxins–which start with our activities elsewhere in the world–sure get around. And all roads seem to point north when it comes to global transport of some of the worst and most persistent of them all.