Insectivorous birds

Rimmer C, McFarland K, Evers DC, Taylor T. 2005. Mercury levels in BicknelFs thrush and other insectivorous passerine birds in montane forests of northeastern United States. Ecotoxicology 14 223-240. 

Birds are comparatively resistant to diflubenzuron, as judged by the ability of the mallard (Anas platyrhynchos) to tolerate single oral doses up to 2000 mg/kg BW or dietary loadings up to 4640 mg/kg ration for 8 days (Table 17.6). Poisoning of insectivorous birds by diflubenzuron, after... 

Likewise, WoodwelPs prediction" of enhancement of the activity of insect pests and some disease agents (which has been demonstrated in the San Bernardino Mountains forest) could lead to an increase in vertebrate species that feed on invertebrates or utilize dead plants for cover. Birds would be the most likely to increase and, to a lesser extent, such small mammals as deer mice, which are partially insectivorous. 

Sometimes, different assessment scenarios are used, for example, to assess risk under contrasting environmental conditions in different geographical areas, or to assess risk to different receptors (e.g., insectivorous vs. herbivorous species of birds). However, it is rarely practical to use more than a small number of scenarios and it is very difficult to determine how well the chosen scenarios represent the full range of true scenarios, especially if the scenarios differ with respect to many variables. 

Consider the following purely hypothetical example assessment for the exposure of an insectivorous bird to a new agricultural insecticide. This insecticide degrades very quickly after application, so that its toxicity dissipates after 24 hours. It does not bioaccumulate, and nonlethal doses are metabolized with no long-term consequences for the bird. These features imply a fairly simple assessment, involving the following expression for computing exposure of a bird to the insecticide within 1 day of its field application... 

The insectivorous bird assessment can be compared to a more traditional probabilistic assessment based on precise distribution functions and particular dependence assumptions. For comparison purposes, we conducted such a simulation. The variable BW was modeled by the same normal distribution with mean 14.5 g and standard deviation 3 g. The variable FIR, on the other hand, was modeled by a log-normal distribution with mean 5.23 and variance 2.3 g per day. The choice of... 

FIGURE 6.15 Outputp -box for dose received by insectivorous birds. 

The insectivorous bird assessment might also require a back calculation seeking a characterization of concentrations that could ensme the doses of insecticide received by the birds are no larger than can be physiologically tolerated. Suppose the toxicologists have collected evidence that doses lethal for the birds occur above 100 pg g" day. Suppose also that regulators have concluded from this information that prudent environmental protection will require that all doses received by birds be less... 

The Carolina wren is primarily an insectivorous bird (94% of diet). It is nonmi-gratory and common in the cotton belt area of the southeastern United States. This species has been frequently observed foraging in or near cotton fields. Total daily intake of the hypothetical pesticide was estimated using the equation... 

For birds and mammals, estimated theoretical environmental concentrations (ETEs) are calculated for granivorous, herbivorous, and insectivorous organisms depending on their size and different groups of crops. Seed treatments are a special item. Based on a large survey of the relevant literature, food intake rates (FIR) and expected residues on feed items (RUD) for these different groups of organisms were collected and representative numbers were fixed in the relevant... 

As an example for the use of field data (in this case, a combination of a generic study, a field-effect study and a field residue study), the following case study is presented the agricultural scenario was a spray application of an organothio-phosphate insecticide in arable crops. Due to the inherent bird toxicity (e.g., LDjq 10 mg a.s./kg bw) estimated according to the EU Guidance Document SANCO/4145/2000, the acute TER is < 0.5 within a Tier 1 risk assessment [1]. Since the trigger value within the EU (> 10) is not met, a refined risk assessment is necessary. As a consequence, a field study was conducted to derive refined exposure parameters for small insectivorous birds in an arable crop. Furthermore, the effects of the product on the population were recorded. The field work of the... 

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