On the same day that I spun off the road on my way to work and landed in a ditch —fortunately sustaining no injuries to myself and minimal damage to my car— a colleague asked me why birds are often seen feeding on the edges of roadways. It so happens that the two things are sort of connected.
Road salt is used for deicing on both sides of the New York-Connecticut border. Not even your nature columnist is going to raise a fuss about a practice that may (in spite of himself) keep him safe in winter. But it’s also true that road salt — usually simple sodium chloride — can have negative impacts on the environment and on wildlife.
I always thought that the sparrows, finches and other birds feeding on the edges of roads were taking advantage of exposed areas where seeds and other food may be more available than they are under the snow. This is probably the case, in part.
But it turns out that some birds also directly ingest road salt, saltwater and grit that are the byproducts of deicing treatments. Most research has focused on “winter finches,†such as American goldfinches, pine siskins, evening grosbeaks and pine grosbeaks, which seem to include salt and grit in their diets. Direct consumption of salt might replace a lack of dietary salt in other foods, while grit is probably a digestive aid. Other animals, notably deer, also take advantage of road salt to add salt to their diets.
Researchers believe that salt may harm wildlife in several ways. First, animals can over-consume salt, which can have toxic effects on them. The toxicity probably does not often cause direct mortality, but it can cause erratic behavior that results in more fatal collisions with cars. When wildlife feed in close proximity to roads, moreover, collisions with cars also increase. Finally, the impacts of road salt on the broader environment can have deleterious results for animals.
Road salt dissolves rapidly and washes quickly into the soil and groundwater. In the soil, it can inhibit the growth of plants within a broad zone near roadsides, which in turn has repercussions for wildlife. Salt from groundwater readily enters lakes and streams, where it can lead to an overbalance of chloride that might be harmful to aquatic plants and animals, although these effects are not well known.
Many towns and states have taken steps in recent years to reduce the environmental impacts of road salts, including using a variety of mixtures and alternative chemicals. Some areas have tried pre-treating road surfaces before storms, which can minimize the amount of salt needed once ice and snow begin to form.
I did not have the opportunity to research this issue in Connecticut thoroughly before press time, but I hope to return to it soon in a future column.
Fred Baumgarten is a naturalist and writer. He can be reached at fredb58@sbcglobal.net. His blog is at thatbirdblog.blogspot.com. 
