CROSSING PATHS NEWS NOTES, WA Dept. Fish & Wildlife
Crossing Paths with Wildlife in Washington's Towns and Cities

January 2013


Can we de-ice our roads without hurting wildlife (ESPECIALLY BIRDS)?

When Washington winter conditions include ice on our roads, driveways and
sidewalks, de-icer applications become a safety necessity. But can we have
safe human travel corridors without hurting wildlife attracted to salt and
grit?

Wildlife biologists say the answer is "maybe" and it depends on what's used
where.

De-icers used by federal, state and local government road crews, as well as
by private citizens at home and work, 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.

Salt based de-icer has been used for over a century in North America and
remains the most commonly used type because it is relatively inexpensive,
available, and effective.

Large mammals, such as moose, elk, deer, bighorn sheep and mountain goats,
are attracted to road salt, which sometimes becomes a factor in motor
vehicle collisions with these big animals.

Perhaps less familiar to most is the attraction to salt by some birds.

"It's all about the salt for winter finches," said Washington Department of
Fish and Wildlife (WDFW) biologist Chris Anderson.

"Winter" or Cardueline finches, of the Fringillidae family, including
siskins, crossbills, grosbeaks, finches, goldfinches and redpolls, are
seed-eaters that move south in winter when seed is scarce in their more
northern breeding areas. They are known to love salt, with research showing
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.

But research shows that birds ingesting relatively small numbers of road
salt granules or small quantities of sodium chloride solutions, are at risk
of sodium poisoning.

Normally the salt glands of birds excrete sodium and chloride to maintain
proper chemical balance. But those glands can be compromised by lack of
access to fresh, open water or exposure to certain pesticides or oil, and
birds die of salt "poisoning" or toxicosis.

Cold weather that freezes areas of freshwater 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 the road salt itself, they are killed when motor
vehicles collide with them on those roads. In fact, some research indicates
salt ingestion increases the vulnerability of birds to vehicle collisions by
causing impairment - they are too weak or slow to avoid moving vehicles.

In one Canadian location - Mount Revelstoke Park -- road mortality of
siskins and other winter finches has been seen frequently enough over the
last 25 years for the birds to be called "grille birds" by the locals, in
reference to their propensity to be collected by the front end of moving
vehicles.

WDFW biologist Ella Rowan, who monitors WDFW's Wildlife Health hotline, says
a call or two every year comes in about whole flocks of dead birds in a
road, usually winter finches and perhaps where they were ingesting
salt-based de-icer.

So what about the other de-icer types?

Acetate-based de-icers include Calcium Magnesium Acetate (CMA), Potassium
Acetate, and Sodium Acetate. Research indicates CMA and potassium acetate do
not attract animals and are harmless to them if ingested. Sodium acetate,
however, may attract animals and contribute to roadkills.

Sand, of course, is natural, usually composed of crushed aggregate or pure
river sand. It has been used to increase road or foot traffic traction at
least as long as salt, but it obviously doesn't have the actual "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.

Washington Department of Transportation (WDOT) wildlife biologist Kelly
McAllister says applying affordable de-icers on our state's roads is vital
to the safety of winter travelers and we need to look for solutions that
don't compromise safety. Acetate-based de-icers are very expensive - usually
in the range of four to five times as expensive as salt-based - they aren't
as effective, and they have high oxygen demand when they run off into
road-adjacent waterways, he says.

"Providing salt sources for wildlife away from roads is something that is
being tried," McAllister said. "I think making open water more available to
birds that are ingesting salt, to reduce the effects of toxicosis, is
another part of the solution, but it's obviously difficult to do on a large
scale during freezing weather. We're open to ideas and citizen help."

WDFW biologists like Anderson and Rowan recommend that wildlife enthusiasts
start at home. Use sand or acetate-based de-icers on sidewalks and
driveways, or if you must use salt, use it very sparingly and keep it stored
out of reach of wildlife. Maintain open water for birds during the winter,
either by replenishing water at least daily or by using a safe bird bath
heater element; keep bird baths clean to avoid spreading disease. Provide
grit (sand or crushed egg shells) in a feeder to reduce the need for birds
to go to roadsides.

And, as always, help birds stay healthy in general by maintaining
year-round, sustainable habitat for wildlife in your own backyard. If you
like watching winter birds close-up by providing supplemental feed, please
keep feeders clean and use clean, dry feed only to avoid spreading disease.