Tree Swallow

From U.S. Geological Survey (USGS):

One of the major problems that environmental contaminants pose to organisms is their ability to build up in the food web. For instance, insects that are exposed to contaminants can then be eaten by birds, who can then pass on the contaminants to their offspring when eggs are laid.

To see how much this process might be affecting Great Lakes tree swallows, we analyzed eggshells from tree swallows from 59 sites across all 5 Great Lakes. Fortunately, in general, we found that levels of contaminants were at or below background concentrations for most sites. The only places we found elevated concentrations were near Midland, Michigan, and the Saginaw River just downstream from Midland, where we found high concentrations of dioxins and furans.

Read more: http://bit.ly/2cB1H6g

Image shows a typical tree swallow (Tachycineta bicolor) studied by the scientists. Photograph credit: Thomas Custer, USGS. #USGS #Science#GreatLakes #Toxicology