HOOK AND FUR
By Bob Brown
This month’s issue of the Washington Department of Fish and Wildlife’s (WDFW) “Crossing Paths” news notes addresses the issue of roadway de-icing and raises the question: Can we de-ice our roads without hurting wildlife?
It is doubtful many of us have given the subject little (if any) thought, and maybe we should. When our roads are covered with ice during winter conditions, de-icer applications become a safety necessity, but can we have safe travel corridors without hurting wildlife attracted to salt and grit? Wildlife biologists say the answer is “maybe,” but it depends on what is used and where.
WDFW biologist Chris Anderson said de-icers used by road crews, as well as private citizens, are mostly one of three types: (1) Salt based, usually sodium chloride or common table salt, but also magnesium chloride, potassium chloride, and calcium chloride, (2) acetate-based, or (3) sand.
The most common de-icer used is salt-based sand because it is inexpensive and effective, but it also attracts some birds. Winter or Cardueline finches, of the Fringillidea family, including siskins, crossbills, grosbeaks, finches, goldfinches and repolls, are seed-eaters that move south in the winter, and they are known to love salt. Research has shown they prefer sodium over other minerals, regardless of size.
Salt is used by birds not only to fill a need associated with a vegetarian diet, but also as grit to aid in the grinding of food in their crops. Birds ingesting even relatively small amount of road salt granules or small quantities of sodium chloride solutions are at risk of sodium poising.
Normally, the salt glands of birds excrete sodium and chloride to maintain a proper chemical balance, but those glands can be compromised by lack of access to fresh water, exposure to certain pesticides or oil, and birds die of salt poisoning or toxicosis. Cold weather that freezes areas of fresh water may force birds to use more saline waters that remain open because of the high salt content, including melted snow on roadways. Using salt water to dilute salt ingestion only makes the problem worse.
If birds aren’t killed by road salt, they are killed when motor vehicles collide with them on roadways. Ingested salt can increase their vulnerability because they are too slow or weak to avoid moving vehicles. In Canada’s Mount Revelstoke Park, so many siskins and other winter finches are killed because of their propensity to be collected in the front end of moving vehicles, locals call them grill birds.
Every year, WDFW receives one or two reports of whole flocks of birds (usually winter finches) dead on our roadways.
So what about other de-icer types?
Acetate-based de-icers include Calcium Magnesium Acetate (CMA), Potassium Acetate and Sodium Acetate. CMA and potassium acetate don’t attract animals and are harmless to them if ingested. However, Sodium Acetate may attract animals and contribute to road kills.
State Department of Transportation (DOT) wildlife biologist Kelly McAllister said sand, usually composed of crushed aggregate or pure river sand, has been used to increase road and foot traffic traction at least as long as salt, but doesn’t have the de-icing effect of salt. Sand has no negative impact on wildlife, but in the amounts needed to keep roadways safe, it is more expensive.
Acetate-based de-icers are very expensive – usually four to five times as expensive as salt-based – and they aren’t as effective, plus they have high oxygen demand when they run off into road-adjacent waterways.
Providing salt sources for wildlife away from roads is something that is being tried. Making open water more available to birds ingesting salt, to reduce the effects of toxicosis, is another part of the solution, but obviously it is difficult to do on a large scale during freezing weather.
WDFW biologists recommend wildlife enthusiasts start at home. Use sand or acetate–based de-icers on sidewalks and driveways, or if you must use salt, use it sparingly and store it out of reach of wildlife. Maintain open water for birds during the winter and provide grit (sand or crushed egg shells) in a feeder to reduce the need for birds to go to roadsides. Also, keep feeders clean and use clean dry food to avoid spreading disease.