Evaluation of factors influencing grit use by birds

Abstract

Appendix 1. Sources of information on grit use by wild birds Appendix 2. Scientific names of avian spedes/subspedes whose common names appear in text, tables or Appendix 1 CHAPTER Vin. GENERAL CONCLUSIONS ACKNOWLEDGMENTS

Evaluation of factors affecting avian risk from granular pesticides

“…It is therefore important to understand the grit characteristics that influence natural grit use by birds, and the influence that diet, body size, and season have on grit consumption. Investigations of grit use by free-ranging birds have shown several patterns regarding the frequency and amounts of grit consumed, the types of particles selected (size, shape, surface texture, composition, and color), and grit retention and turnover in the gizzard (see [24] for a discussion).…”

“…Grit found in the gizzards of free-ranging birds consisted mainly of quartz particles (e.g., [34,37]), which may indicate a preference for quartz. On the other hand, quartz is often readily available, and it may tend to stay in the gizzard longer than other particles because of its hardness and insolubility [24]. Feldspar has also been found in birds' gizzards (e.g., 37,38]) and is also hard and insoluble, but it is not found as frequently as quartz.…”

“…Such variations can affect whether or not a bird will intentionally ingest a pesticide granule (Best and Gionfriddo, 1994a,b). Granule ingestion by birds also can be affected by granule size and color (Gionfriddo and. Further, other factors such as pesticide load per granule, soil color and texture, weather conditions, the number of pesticide applications per season, application methods, bird foraging behaviors, etc.…”