Impacts of carbofuran on birds in Canada and the United State - Carbofuran and Wildlife Poisoning: Global Perspectives and Forensic Approaches - page 243

involving birds of prey in the United States and Canada, respectively, were the result of abuse. For all
organophosphorous and carbamate insecticides pooled, the proportion of abuse cases was 54% for the
United States and 35% for Canada - showing that carbofuran is often a preferred pesticide for abusive
poisoning. Indeed, carbofuran accounted for 75% of all known organophosphorous and carbamate
abuse cases and 50% of Canadian cases. Some species have borne the brunt of abusive poisonings.
For example, the fi nding of poisoned golden eagles ( Aquila chrysaetos ) is almost always associated
with abuse cases, typically stemming from attempts to poison them directly or efforts to poison large
predators such as coyotes ( Canis latrans ). Allen, Veatch, Stroud et al. (1996) described how Furadan
4F was applied to sheep carcasses and persisted at levels capable of killing eagles and hawks for at
least two months. Wobeser and colleagues (2004) summarised cases in Western Canada occurring
between 1993 and 2002. A total of 54 separate incidents resulted from the use of cholinesterase inhib-
iting insecticides with either bald or golden eagle as the species involved in the incident. The identity
of the toxicant was only possible for eight of these incidents and all eight were carbofuran cases (sev-
eral incidents were diagnosed from cholinesterase assays only and samples were not sent for analysis).
8.7 Conclusions
Insecticides such as carbofuran came into use in the late 1960s with the expectation of avoiding the
environmental problems associated with persistent organochlorines. The relatively rapid breakdown
of carbofuran under most conditions (its long persistence in acid soils had not been discovered at the
time) allowed it to be rapidly registered for a wide variety of uses. However, soon after its introduc-
tion, wildlife managers and regulators began to raise concerns about its high toxicity and ability to
kill birds under many different circumstances.
The copious data reviewed in this chapter provide compelling documentation of the lethality
of carbofuran to birds when used under operational conditions. Kills have been documented with
every formulation, and under a wide variety of use patterns and crops. Attempts to reduce or miti-
gate impacts through draconian controls and extensive changes to standard agricultural practices
have had mixed success and, in some cases, have failed completely (for example, refer back to
Section 8.2.1.7 for attempt in the State of Virginia). Given that few State or Provincial jurisdictions
in the United States or Canada have adequate resources to detect, investigate, and document fi sh and
wildlife kills, the extent of data summarised in this chapter is even more remarkable. Considerable
fi eld data unequivocally affi rm that there are no known circumstances under which carbofuran can
be used without killing birds, perhaps not following every application but with a very high prob-
ability. Carbofuran gained such notoriety as a bird killer in North America that even professional
ornithological associations took notice and petitioned government for a cancellation (e.g., American
Ornithologist's Union 1990).
Unfortunately, as reviewed by Mineau (2004), regulatory changes associated with bird protection
have tended to move at a glacial pace in North America. More than 40 years after the pesticide's
introduction, the last remaining uses of carbofuran have fi nally been cancelled in both Canada and
the US although legal challenges from the manufacturer are probably not over (as discussed in the
Conclusion). It is sobering to ponder the diffi culties in store for developing countries that would like
to similarly protect their environment and their birdlife in particular.
Acknowledgements
The fi ndings and conclusions in this chapter are those of the authors and do not necessarily represent
the views of Environment Canada, the US Fish and Wildlife Service or the California Department
of Fish and Game. We are indebted to Nick Mastrota, the US EPA and the US Fish and Wildlife