Environmental Engineering Reference
In-Depth Information
Exp.1
Exp.2
Exp.5
Exp. 7
700 m
Exp.3
10 km
Exp.4
T2
T1
Exp.6
T1
T2
T1
T1
T2
70 m
T2
T1
T3
70 m
T2
Figure 7.3
Field design of plots in all seven experiments (Exp.) for evaluating the impact of seeds
treated with carbofuran and Rhodamine B consumption on wild birds, where: T1 - red seeds treated
with carbofuran and Rhodamine B; T2 - red seeds treated with carbosulfan and Rhodamine B;
T3 - red seeds treated with carbofuran and methiocarb. Distances between plots of the same
experiments were 70 m, 700 m and 10 km
blackbird. All these species are common in rural areas, and sometimes cause damage to corn, wheat,
rice and soya crops in the Brazilian States of São Paulo, Paraná and Mato Grosso do Sul.
Details regarding the 13 species and 465 birds found dead in the experiment are given in
Table 7.3. Data includes partial carcasses and feather spot data, which represents birds that were par-
tially consumed or totally removed by predators. Granivorous birds represented 97% of the species
poisoned. The eared dove was most common, which accounted for as much as 89% of the total num-
ber of individuals found dead (see Figure 7.4). This species increased in numbers dramatically in the
1980s, especially in the State of São Paulo. As a result, large productive colonies supply nutritional
support for a range of predatory species, such as the southern crested caracara (
Caracara plancus
)
and the roadside hawk (
Rupornis magnirostris
). Such predators regulate these agricultural pests, and
can be very abundant as observed, for example, in large groups of crested caracaras.
Although only two roadside hawks were found dead (refer to Table 7.3), the behaviour of this
species and that of the southern crested caracara (seen attacking, removing and carrying poisoned
birds in fl ight, probably to their chicks), was documented in four experiments.
Numerous attacks by predators were also detected from the piles of feathers found (i.e., feather
spots), and it was possible to distinguish the actions of predatory mammals of the carnivorous order,
by identifying dental cuts on feather spines (the calamus). By dissecting the digestive system of one
of the roadside hawks, we revealed that it had eaten an eared dove. Parts of the dove were found in the
hawk's throat, its gizzard and its proventriculus. Feathers, various parts of the bird's digestive system,
and fi ve wheat seeds treated with carbofuran and Rhodamine B were also found. These observations
confi rmed that predators are victims of secondary poisoning, and indicated that birds and mammals
which attack dead or dying granivorous birds can be poisoned.
Predator poisoning can cause wide ranging environmental impacts and may harm the potential
for survival of various already fragmented populations. Likewise, the biological stability between
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