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Table 2. Organochlorine insecticides still in use in North America.
Compound Issues of concern
Dicofol Egg-shell thinning, bioaccumulation, and
effects on behaviour and reproduction
Methoxychior Aquatic impact and accumulation in fish
Endosulfan Aquatic impact
Lindane Widespread contamination by other
benzenehexachlorides (BHCs)
Toxic organophosphate and carbamate insecticides
These two classes of cholinesterase-inhibiting insecticides currently account
for the majority of insecticides registered world wide. As mentioned previously,
birds are ill-equipped to deal with these products. Grue et al. (1983)
concluded that kills were largely predictable on the basis of toxicity and extent
of use. Because these products are short-lived, problems have generally arisen
from situations where there was a clear route of exposure.
Foliage eaters
Consumers of freshly sprayed foliage obviously represent a high-risk
category. Grazing or browsing species must ingest large quantities of nonnutritious
foodstuffs. Some, such as waterfowl, have inefficient digestive
systems and compensate by bulk feeding. In addition to the previously
described diazinon example, other problems with anticholinesterase insecticides
include die-offs of ducks and geese in alfalfa fields treated with
carbofuran (Hill and Fleming 1982) and of Sage Grouse (Centrocercus
urophasianus) feeding on alfalfa crops treated with dimethoate or on potato
foliage and weeds sprayed with methamidophos (Blus et al. 1989).
As a result of widespread waterfowl mortality, the use of diazinon on turf grass
(golf courses and sod farms) was banned in the USA. With increased aware- -
ness of this problem, other cases began to be reported, for example, in Canada
(Frank et al. 1991). Carbofuran is currently under review in Canada, in part
because of its use in waterfowl-breeding habitats and the demonstrated
problem with waterfowl mortality in alfalfa fields.
Granular insecticides
Granular formulations of insecticides are notorious for promoting hazardous
exposure. A number of products have been linked to massive bird kills and to
some cases of mammalian mortality as well. These products are used worldwide
on crops, such as corn (maize), rice, and rapeseed. The granules themselves
are attractive to birds and possibly other species. Depending on the
specific granule base, birds mistake them for grit or seeds or both (Balcomb
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