Trophic Relations of the Red-Necked Grebe on Lakes in the Western Boreal Forest: A Stable-Isotope Analysis.

• Author(s) / Creator(s)

  • Tonn, W. M.
  • Klatt, P. H.
  • Paszkowski, C. A.
  • Gingras, B. A.
  • Wilcox, K.

• We compared trophic ecology of grebes inferred from stable-isotope analysis to that from gut contents, and compared isotopic ratios of Red-necked Grebes (Podiceps grisegena) from lakes differing in their food webs. Analyses of different grebe tissues (egg yolk and albumen, pectoral and leg muscle, breast and primary feathers) also allowed us to assess the effectiveness of these tissues at representing grebe trophic relations. Isotopic ratios from pectoral and leg muscles were similar, based on comparisons within individual birds. Enriched values of d15N and d13C suggested that breast and primary feathers were molted over winter, and therefore reflected a marine food web. Albumen and yolk of grebe eggs and muscle tissues from downy chicks, however, matched isotopic characteristics of the local food web, indicating that female Red-necked Grebes use nutrients from the breeding lake for egg formation. Eggs, therefore, can provide excellent material for isotopic analysis aimed at assessing trophic relations of Red-necked Grebes on breeding lakes. Gut contents and stable isotopes both indicated that grebes from lakes with fish consumed a mixed diet of fish and macroinvertebrates and occupied the highest trophic level, at or above the level of piscivorous fishes. In contrast, grebes from lakes lacking fish occupied a lower trophic position.

• Date created

  2004

• Subjects / Keywords

  • Food web
  • Egg
  • Stable-carbon isotope ratios
  • Diet
  • Podiceps grisegenga
  • Stable-nitrogen isotope ratios
  • Red-necked Grebe

• Type of Item

  Article (Published)

• DOI

  https://doi.org/10.7939/R3J960M65

• License

  © The Cooper Ornithological Society 2004