Bird response to grit and pesticide granule characteristics: Implications for risk assessment and risk reduction

Abstract

Granular pesticides (insecticides and nematicides) pose a hazard for birds because of the potential for birds to ingest the granules. Avian risk from granular pesticides is currently assessed by using a U.S. Environmental Protection Agency risk index based on the acute toxicity of the pesticide, the pesticide concentration on the granules, and the number of granules available on the soil surface after application (LD50/ft2). Recent evaluations have demonstrated that avian response to pesticide granules as a source of grit also can influence exposure to pesticide granules; such information should be included in the risk assessment process. Herein we review the limitations of the current risk assessment process and summarize the extant information regarding bird response to grit and granule characteristics (i.e., granule carrier type, color, size, shape, and surface texture) and pesticide load per granule. Suggestions are made for assessing and reducing avian risk from granular pesticides by testing granular formulations against standards for various granule characteristics and by using frequency distributions of avian responses to granules. Granule characteristics selected as standards should be similar to grit used by free‐ranging birds (e.g., silica particles, earth‐tone hues). Comparisons of granular formulations against the standards would demonstrate the potential for birds to consume pesticide granules as grit, relative to naturally occurring particles. Frequency distributions constructed for grit sizes used by birds and gizzard grit counts can be used to estimate the effect of granule size and pesticide load per granule, respectively, on avian risk. Because bird response to pesticide granules is highly variable, we recommend using probabilistic approaches when assessing avian risk from pesticide granules to account for the ranges of response.

Risk assessment for Birds and Mammals

“…The grit retention time of 0.24 days represents one of the shortest reported retention times in the literature. In Stafford and Best (1999), however, the conversion of 4.2 was already questioned for the following reasons: (i) it was based on a single species and the granules were intermixed with dog food and thus the birds consumed them unintentionally; (ii) the administration of granules mixed with canned dog food limited the bird requirement for grit since the diet was considered atypically soft.…”

Plant-Parasitic Nematodes Attacking Olive Trees and their Management

“…NFNs can be applied postplanting either by chemigation with emulsifiable concentrates, or by mixing granular formulations into the soil. The opportunity for using the latter mode must be checked in each particular country, because the use of granular pesticides is being progressively prohibited by many regulatory agencies due to avian risk (90). There is a scarcity of data concerning postplanting treatment with NFNs in olive orchards.…”

Factors affecting intentional bird poisoning on bean farms in Taiwan: seeding methods and the presence of adjoining duck farms matter

“…Granular carbofuran was another option to reduce bird damage that was promoted in early agricultural articles in Taiwan (Hong et al 2018). There is much evidence that carbofuran granules are ingested by birds with lethal consequences (Balcomb 1983, Stafford and Best 1999, Mineau et al 2011. It is currently controversial whether such killing of pest birds is illegal given that the Taiwanese Wildlife Conservation Act gives farmers the right to protect their crops.…”