Abstract

The need for consistent and reliable methods for rating body condition in individual animals exists across the animal kingdom, for clinical health assessment of captive individuals as well as for research involving free-ranging populations. Body condition evaluation for avian species traditionally relies upon subjective palpation scores or post-mortem evaluation of muscle mass and fat stores.

A study set of 46 adult herring gulls resulting from a population management cull along the Outer Banks of North Carolina was evaluated by several external measures to compare with pectoral muscle wet weight as the gold standard of body condition. Body weights and external morphometric measurements were collected for all specimens post-mortem but prior to any dissection or manipulation. A goniometer was used to obtain an objective measure of the angle of the pectoral muscles off the bony keel, a technique that can easily be applied to a live specimen in hand. A technique previously described for measuring the depth of the pectoral musculature using ultrasound in other avian species was performed on each intact bird.¹ Muscle depth in the same site was also measured via ultrasound after the removal of the overlying skin to determine the level of variability introduced by feathers and trapped air as it would be in a live bird.

A cohort of 33 individual observers evaluated a subset of 21 birds across a range of condition using a 9-point subjective scoring system based upon palpation of the pectoral muscles adjacent to the keel. As expected, the subjective palpation scoring system demonstrated an extremely high level of inter-observer variability. Both goniometer angle and ultrasound pectoral muscle depth measurements demonstrated stronger correlation with the available post-mortem analysis of body condition, and may present viable options for subjective evaluation of body condition in live avian species.

Acknowledgements

The authors gratefully acknowledge the extensive technical contributions of Heather J. Broadhurst to this work.

* Presenting author
+ Student presenter

Literature Cited

1.  Dietz MW, Dekinga A, Piersma T, Verhulst S. 1999. Estimating organ size in small migrating shorebirds with ultrasonography: an intercalibration exercise. Physiol Biochem Zool 72(1): 28–37.