A Latin American perspective: the environmental impact of farming wheat and rice treated with carbofuran and Rhodamine B on Brazilian wild birds - Carbofuran and Wildlife Poisoning: Global Perspectives and Forensic Approaches - page 201

Table 7.4 Rate of dead birds recovered per day during the experiments with carbofuran,
carbosulfan and methiocarb

Number of the Experiment Seed Treatment Number of Dead Birds Mean and StDev

4 Carbofuran 109 13.6 ± 7

4 Carbosulfan 40 5 ± 5.5

6 Carbofuran 82 32 ± 19.42

6 Carbosulfan 21 6 ± 5.7

6 Methiocarb 62 20 ± 13.01

Given these points, we must consider that: i) poisoned birds may leave the test plot); ii) carbosul-
fan does not act as a secondary repellent which interrupts consumption; iii) birds poisoned with car-
bosulfan may have a greater tendency to reach the adjacent forest, where they may be preyed upon
by forest species, some of whom have a higher 'conservation value'; iv) birds affected by carbo-
sulfan may seek refuge in denser vegetation, and may therefore be hidden from farmers, researchers
and hence, public opinion.
These points raise questions regarding the principle that carbosulfan (which is 20 times less
potent) could be used as a substitute for carbofuran. The fi ndings reported here suggest that carbo-
sulfan is probably not an effective alternative to carbofuran. Although carbosulfan is (on paper, for a
limited number of species tested) less toxic, birds that ingest only a few seeds treated with carbosul-
fan may still not survive. For example, only six or seven rice seeds were enough to kill several eared
doves (n 4). The capacity for a bird to recover from nominal ingestion of a few carbosulfan-treated
seeds is also unknown.
The possible repellent effects of methiocarb and carbosulfan, as tested in experiment 6, were not
statistically proven (Table 7.4). In the treatment with methiocarb, 62 birds died (and an average of 20
individuals died per day); while similar results were obtained using carbofuran, where 82 birds died
at a rate averaging 32 per day. Although fewer birds died when carbosulfan was used (21 individu-
als at 6 deaths per day), as in the previous experiment, many birds visibly affected by carbosulfan
escaped the test plot, making an accurate estimation of mortality diffi cult.
Although certain authors have indicated that methiocarb may act as a secondary repellent in birds
(Nelms and Avery 1997; Avery, Tillman and Laukert 2001; Avery 2002), its use in association with
carbofuran was limited. Carbofuran is an extremely toxic pesticide, and only one treated seed is
needed to kill a small or medium sized bird. Thus, the toxicity of carbofuran simply over-rides any
potential benefi ts that could be gained from adding methiocarb. Moreover, no warning communica-
tion between birds was observed, nor any signs of aversion due to the ingestion of carbosulfan or
methiocarb, which would have reduced seed consumption.

7.3.2 Avian mortality and some aspects that infl uence this estimate

The following farming practices and factors may infl uence the accurate estimation of mortality rate,
and must be taken into consideration when determining how to mitigate mortality:

i) movements of machinery and other farming activities

ii) regulation of sowing machinery

iii) presence of roots, plant debris (litter), and surface depressions of the soil which impede the
burial of seeds