61
3.2.1 Cultivation Practices May Influence Likelihood
of Exposure
Probability of exposure to pesticides in birds is directly linked with the agricultural
practices, like timing of pest control in a particular area for a seasonal crop (Narváez
et al. 2016; Santos et al. 2016). A study by Osten et al. (2005) with black-bellied
whistling duck (Dendrocygna autumnalis) reported the direct correlation during the
period between pesticide application for specific agronomic purposes and significant
inhibition of ChE activity due to exposure to anticholinesterase agents (organophosphate and carbamates). Further, secondary poisoning (like mortality of raptors due to
consumption of contaminated songbird) is also evident due to pesticide application
(Mineau et al. 1999). Therefore, coordinating time with pesticide applications and
bird’s annual cycle is necessary to avoid secondary poisoning. Though most of the
second-generation pesticides are biodegradable, some of them may persist for a few
months in the environment, water-logged fields, etc. making them available for exposure to birds (Mineau et al. 1999). Pesticide exposure rate to birds also depends upon
its applications in croplands in different seasons. As for example, in Switzerland
granular carbofuran was applied for seed protection in every spring which was linked
to the declining of raptor population in spring (Dietrich et al. 1995). Similar findings
have been reported by Mineau et al. (2005) in North American canola fields, where
insecticides were applied from mid-May to early-June when migratory songbirds
and geese were residing in the canola fields resulting in population reversal in those
bird species. In some cropland, exposure risk reduces during growth period of the
crops, because some birds prefer to spend time during seedling period of the crop
rather than budding stages (Corson et al. 1998).
3.2.2 Types of Pest That Increase Risks of Pesticide
Intoxication to Birds
Exposure of pesticides to birds depends upon the insect species they feed on, as
pesticides are linked to pest control; therefore, birds feeding on insect pests of
agriculture fields are more likely to be exposed to chemicals. Some insect species
constitute a large fraction of a bird’s aliment, which may be the target of particular
pesticides. Rapid re-emergence of a pest or relative abundance in a crop field also
prompts heavy pesticide applications (Cutler 2012; Qu et al. 2017). Pest resurgence may occur due to the application of less degradable and wide-ranging pesticides that terminate the native predators to a particular pest, or due to eradication
of a primary pest that helps to flourish the secondary pests to emerge and become
the major pest (Dhaliwal et al. 2006; Gill and Garg 2014). Pest outbreaks allure
avian species and thereby unravel the strong possibility of vulnerability of birds to
pesticides. Reports revealed the reappearance of bed bug (Cimex lectularius)
(Davies et al. 2012), cotton bollworm (Helicoverpa armigera) (Mironidis et al.
3 Toxic Effects of Pesticides on Avian Fauna
3.2.1 Cultivation Practices May Influence Likelihood
of Exposure
Probability of exposure to pesticides in birds is directly linked with the agricultural
practices, like timing of pest control in a particular area for a seasonal crop (Narváez
et al. 2016; Santos et al. 2016). A study by Osten et al. (2005) with black-bellied
whistling duck (Dendrocygna autumnalis) reported the direct correlation during the
period between pesticide application for specific agronomic purposes and significant
inhibition of ChE activity due to exposure to anticholinesterase agents (organophosphate and carbamates). Further, secondary poisoning (like mortality of raptors due to
consumption of contaminated songbird) is also evident due to pesticide application
(Mineau et al. 1999). Therefore, coordinating time with pesticide applications and
bird’s annual cycle is necessary to avoid secondary poisoning. Though most of the
second-generation pesticides are biodegradable, some of them may persist for a few
months in the environment, water-logged fields, etc. making them available for exposure to birds (Mineau et al. 1999). Pesticide exposure rate to birds also depends upon
its applications in croplands in different seasons. As for example, in Switzerland
granular carbofuran was applied for seed protection in every spring which was linked
to the declining of raptor population in spring (Dietrich et al. 1995). Similar findings
have been reported by Mineau et al. (2005) in North American canola fields, where
insecticides were applied from mid-May to early-June when migratory songbirds
and geese were residing in the canola fields resulting in population reversal in those
bird species. In some cropland, exposure risk reduces during growth period of the
crops, because some birds prefer to spend time during seedling period of the crop
rather than budding stages (Corson et al. 1998).
3.2.2 Types of Pest That Increase Risks of Pesticide
Intoxication to Birds
Exposure of pesticides to birds depends upon the insect species they feed on, as
pesticides are linked to pest control; therefore, birds feeding on insect pests of
agriculture fields are more likely to be exposed to chemicals. Some insect species
constitute a large fraction of a bird’s aliment, which may be the target of particular
pesticides. Rapid re-emergence of a pest or relative abundance in a crop field also
prompts heavy pesticide applications (Cutler 2012; Qu et al. 2017). Pest resurgence may occur due to the application of less degradable and wide-ranging pesticides that terminate the native predators to a particular pest, or due to eradication
of a primary pest that helps to flourish the secondary pests to emerge and become
the major pest (Dhaliwal et al. 2006; Gill and Garg 2014). Pest outbreaks allure
avian species and thereby unravel the strong possibility of vulnerability of birds to
pesticides. Reports revealed the reappearance of bed bug (Cimex lectularius)
(Davies et al. 2012), cotton bollworm (Helicoverpa armigera) (Mironidis et al.
3 Toxic Effects of Pesticides on Avian Fauna