Environmental Engineering Reference
In-Depth Information
Figure 7.4 Eared dove ( Zenaida auriculata ) was the species of bird that incurred the most deaths.
This photo shows one of the 365 eared doves that died after consuming wheat seeds treated with
carbofuran and Rhodamine B. Beside it (highlighted by the arrow) is one of the seeds that had not
been buried during the seeding process, remaining dangerously exposed to other granivorous birds.
Photo taken by Álvaro Fernando de Almeida
Eleven insectivorous birds (refer to Table 7.3) that died with symptoms of carbofuran poisoning
were unexpected victims, since no treated seed was found in their digestive tract. The possible mode of
poisoning in this case is not clear, but such data indicates a potential danger may exist to these species.
We also found several burrowing owls ( Athene cunicularia ) and a roadside hawk (see Figure 7.5)
dying with contracted pupils and compromised motor coordination. The roadside hawk was found
beside its regurgitated food, in which only arthropod remains were noted. The digestive systems of
the burrowing owls, American kestrel ( Falco sparverius ), great kiskadee ( Pitangus sulphuratus ),
white-eared puffbird ( Nystalus chacuru ) and the other insectivores were also empty. This may sug-
gest that these species regurgitated any food carrying the poison. Vomiting is in itself a sign of
carbofuran poisoning (see Chapter 2). It is possible that the powdered dye used to camoufl age seed
poisoned arthropods which were then consumed by insectivorous birds. During sowing with cam-
oufl aged seed, clouds of dust were often kicked up by the sowing machines (Almeida, Couto and
Almeida 2010a).
The capacity of certain birds to regurgitate poisoned seed may also contribute to a decrease
in their mortality (Pascual, Hart and Fryday 1999). The digestive systems of several other dead
granivorous birds (four individual Chopi blackbirds, house sparrow ( Passer domesticus ) and spotted
nothura ( Nothura maculosa )) were also found to be empty.
Some birds were found poisoned with a few carbofuran-treated seeds still in their crops,
which is used as a temporary pre-digestive food store and not for nutrient absorption. Seven
dead ruddy ground doves were found with one or two seeds, and 25 eared doves died with only
one seed in their crop (see Figures 7.4, 7.6 and 7.7). These observations indicate that carbo-
furan, even in extremely small amounts, can be absorbed via the avian crop, perhaps through
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