Effects of experience and a visual aid on ptilochronology.

Ptilochronology, the study of feather growth bars, has been used to assess nutritional condition, yet the implementation of this technique can be challenging. This study investigated how a magnification aid and level of experience with the technique affected the variability and accuracy of ptilochronology measurements. The average width of growth bars was significantly narrower when made with a magnifying visor as opposed to the unaided eye, suggesting that future ptilochronology studies should incorporate magnification. Measurements were also influenced by the measurer's level of experience, suggesting that a learning curve must be taken into account when analyzing ptilochronology results. [ABSTRACT FROM AUTHOR]