An Evaluation of Condition Indices for Birds

Authors

Douglas H. Johnson, USGS Northern Prairie Wildlife Research CenterFollow
Gary L. Krapu, USGS Northern Prairie Wildlife Research CenterFollow
Kenneth J. Reinecke, USGS Northern Prairie Wildlife Research Center
Dennis G. Jorde, USGS Northern Prairie Wildlife Research Center

Date of this Version

1985

Comments

Published in the Journal of Wildlife Management . 49(3):569-575.

Abstract

A Lipid Index, the ratio of fat to fat-free dry weight, is proposed as a measure of fat stores in birds. The estimation of the index from field measurements of live birds is illustrated with data on the sandhill crane (Grus canadensis) and greater white-fronted goose (Anser albifrons). Of the various methods of assessing fat stores, lipid extraction is the most accurate but also the most involved. Water extraction is a simpler laboratory method that provides a good index to fat and can be calibrated to serve as an estimator. Body weight itself is often inadequate as a condition index, but scaling by morphological measurements can markedly improve its value.