Crustal Geophysics and Geochemistry Science Center

Integrated Methods Development Project

Bioaccessibility of Metals in Sediment to Tree Swallows near Montezuma, Colorado

Subtask Objectives

Contaminants associated with mining can impact biota at many levels within an ecosystem. Christine and Thomas Custer have been using tree swallows as indicators of environmental contamination in areas across the United States (Custer and Custer, 2003; Custer and others, 2003). Tree swallows feed on emergent aquatic insects near their nests (near being within a few hundred meters diameter) and offer the ability to assess bioavailability of metals from contaminated sediments into aquatic insects, and into higher trophic levels. Hence, elemental residues within the tissues and organs of nestling swallows reflect bioavailability of these elements in local sediments.

Several leaching and extraction techniques have been developed to assess potential bioavailability or bioaccessibility of metals from soils and sediments. In this study, we will subject composite samples of sediments or soils collected in close proximity to tree-swallow nests to various leaching methods. Leachates will be analyzed and results compared with analyses of tree swallow livers, fecal material, and food sources. Leaching methods will be evaluated as to their ability to determine the potential bioaccessibility of elements within the sediments.

The objectives of this work are to (1) determine the bioavailability of metals to tree swallows from sediments and soils in areas of different geological characteristics, and (2) evaluate the usefulness of various leaching techniques to estimate bioavailability of metals from sediments and soils.


Custer, C.M., and Custer, T.W., 2003, Tree swallows: a nationwide sentinel species for assessing and monitoring aquatic contamination: U.S. Geological Survey Upper Midwest Environmental Sciences Center Fact Sheet 2003.3. (Can be accessed online at

Custer, C.M., Custer, T.W., Archuleta, A.S., Coppock, L.C., Swartz, C.D., and Bickham, J.W., 2003, A mining impacted stream: exposure and effects of lead and other trace elements on tree swallows (Tachycineta bicolor) nesting in the Upper Arkansas River Basin, Colorado, in D.J. Hoffman, B.A. Rattner, G.A. Burton, Jr., and J. Cairns, Jr., eds., Handbook of Ecotoxicology, 2nd Ed.: Boca Raton, Florida, Lewis Publishers, pp. 787-812.



  • Custer, C.M., Yang, C., Crock, J.G., Shearn- Bochsler, V., Smith, K.S., and Hageman, P.L., 2009, Exposure of insects and insectivorous birds to metals and other elements from abandoned mine tailings in three Summit County drainages, Colorado: Environmental Monitoring and Assessment, 153 (1-4), pp. 161-177, doi: 10.1007/s10661-008-0346-y.
  • Smith, K.S., 2007, Strategies to predict metal mobility in surficial mining environments, Chapter 3, in DeGraff, J.V., ed., Reviews in Engineering Geology, v. 17, Understanding and Responding to Hazardous Substances at Mine Sites in the Western United States: Geological Society of America, pp. 25-45.

Contact Information

Kathleen Smith
Box 25046 MS 964D Denver Federal Center
Denver, CO 80225-0046
Phone: 303-236-5788
Email: Kathleen Smith

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