HUI, C.A.*; BEYER, W.N.: Sediment Ingestion of Two Sympatric Shorebird Species

Ingestion of sediment during feeding is normal among many wildlife species. The consumption of contaminants from this source may be greater than that from the rest of the diet. For example, the principal source of health-impairing amounts of lead in Wood Ducks (Aix sponsa) at one site is sediment even though sediment ingestion is only about 1% of the total diet. Earlier reports show that birds commonly ingest much more than 1% sediment in their diet. Our study compared sediment ingestion by two species of shorebirds that are common in California coastal and wetland areas: Black-bellied Plovers (Pluvialis squatarola) and Willets (Catoptrophorus semipalmatus). We sought to relate sediment ingestion to bill length and to feeding behavior with hopes of discerning some predictable parameters. Predictability would enable estimates of the potential threat to individual species by direct ingestion of contaminated soils. Black-bellied Plovers have short bills and peck while foraging, whereas Willets have long bills and probe with bills open in sediments. We anticipated that Willets would ingest more sediment than the plovers. Intestinal digesta were collected from these birds while over-wintering at the same beach. We used four different techniques: acid-insoluble ash and elemental markers of Al, Fe, and Ti in digesta. Results were similar. Plover digesta contained 29% sediment, and Willet digesta contained only 3% sediment. These results are contrary to expectations. Sediment ingestion may be species specific and not linked to bill length or to probing behaviors.