There have been many documented cases of bird mortality along roadsides where salt was applied. Herbivorous and granivorous species, especially, are attracted to salt, probably to satisfy a dietary need. Because mortality appears to be primarily a result of vehicle strikes, most authors have assumed that salt was only indirectly responsible for the deaths—a case of “fatal attraction” to busy salted roads. Repeated observations of apparent behavioral toxicity along roadsides, as well as new information on the toxicology of oral salt ingestion in birds, now suggest that salt toxicity per se is contributing to the vulnerability of small songbirds to road traffic and perhaps is a direct cause of mortality in some birds. The difficulty of retrieving bird carcasses and the low rate of reporting suggest that kills probably are more widespread and frequent than indicated by documented reports alone. Most known cases of songbird mortality have occurred within a group of birds collectively known as winter finches belonging to the subfamily Carduelinae. This may result from a higher probability of exposure for these species because of their diet and presence in the snow belt but also may reflect a greater ease of detecting mortality incidents in species forming large feeding flocks. The high attraction of salted roads for winter finches suggests that the roads' ecological footprint is very large. We conclude that the importance of road salt as a mortality factor in these species long has been under-estimated by wildlife managers and transport personnel.
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1 September 2005
Road salts and birds: an assessment of the risk with particular emphasis on winter finch mortality
Pierre Mineau,
Lorna J. Brownlee
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bird mortality
car strikes
road salt
Sodium chloride
winter finches