Impacts of carbofuran on birds in Canada and the United State - Carbofuran and Wildlife Poisoning: Global Perspectives and Forensic Approaches - page 224

and scavenging rates (McKinnon in a letter to PMRA). Using three separate methods to analyse the
results, the Pesticides Management Regulatory Agency concluded that the study demonstrated a kill
rate ranging from 0.62 to 1.3 kills per hectare on seeded fi elds (PMRA 1998).
These kill rate estimates are clearly lower than those estimated from the use of the silica granu-
lar formulation. However, this study was not able to incorporate a test of the risk to large fl ocks
of migrant birds as uncovered in one of the documented incidents (refer to the case detailed in
Section 8.3.2.1). Using survey data and assumptions of the turnover rate of birds visiting treated
fi elds, the PMRA estimated that between 27 and 100% of the birds of fi ve different species would be
killed if they landed in a treated fi eld.
8.3.2 Reported incidents
8.3.2.1 May 1984, canola (rapeseed), Vonda, Saskatchewan
This is the fi rst of two incidents reported for canola crops in Canada. The Canadian Wildlife Service
obtained details of this incident from the investigating pathologist at the University of Saskatchewan
and from the farmer who had seeded the crop. One of us (P. Mineau) estimated that more than
2 000 Lapland longspurs ( Calcarius lapponicus ) died in this incident. One notable feature of this
kill was that the mixture of seeds and granules was broadcast with an air seeder and then harrowed
(i.e., mechanically incorporated into the soil). According to the farmer, this was a common practice
in the area, a fact that was confi rmed independently (R. Atkins, Alberta Farm Machinery Institute,
personal communication). Air seeders are used either to broadcast the canola seed or, alternatively, to
position the seeds at a very shallow depth. In either case, the fi elds are then harrowed and packed.
This kill is on the record because a fl ock of birds landed in a freshly seeded fi eld and, more impor-
tantly, the farmer saw the event and reported it. Even kills involving very large numbers of birds are
unlikely to be reported because the birds are cryptic, the fi elds isolated, and the farmers are unlikely
to return to the fi elds until the crop germinates. If growers do witness kills, they may be unaware
of the importance of reporting their observations to wildlife authorities. The incident was also note-
worthy in that it established the attractiveness of the Furadan CR-10 formulation to songbirds.
This incident pointed to a serious issue for Canada. Granular carbofuran was used in canola for
the prophylactic control of fl ea beetles (Chrysomelidae, Lamb and Turnock 1982) over extensive
areas of the northern prairies (between 0.37 and 0.54 million hectares yearly from 1981 to 1985;
Madder and Stemeroff 1986). The peak canola seeding period is in mid-May (Alberta Agriculture
1985), which coincides with the time when the largest fl ocks of migrants such as Lapland longspurs
traverse the prairies. Of particular concern are those species that migrate in very large fl ocks and use
open agricultural land for foraging (e.g., horned larks, Lapland longspurs, buntings ( Emberizidae )).
There are reports of Lapland longspur fl ocks covering entire quarter sections (64 hectares) of the
level open farmland in east-central Saskatchewan (Houston and Street 1959). Flocks of 10 000 or
more birds are common (Nero 1962; Lister 1964; Hatch 1966; Houston 1971, 1972; Renaud 1973;
Gollop 1986, 1987). Clearly, a few 'incidents' such as the one recorded in 1984 could have serious
consequences for the populations of some of these species. Although large fl ocks of migrants are our
main concern, there is also an ever-present risk to the locally breeding birds that frequent agricultural
fi elds. (For another example of the risk to migrants posed by carbofuran and of the possible repercus-
sions, the reader is referred back to Chapter 3).
A retrospective analysis by Mineau and colleagues (2005) investigated the relationship between
the abundance of 29 bird species through a breeding bird survey and a granular use index for the
Canadian Prairies. They found signifi cant negative correlations for several species, suggesting that
granular insecticides (primarily carbofuran but terbufos also) affected birds on a population level
despite being used on a relatively small proportion of the total agricultural area.