Do Short-tailed Shearwaters shrink once dead? Comparing study skins with live specimens

Stephen Totterman (Empire Vale, New South Wales, Australia) writes on-line in the open-access journal Marine Ornithology on differences in measuring Short-tailed Shearwaters Puffinus tenuirostris as study skins or live specimens

The paper’s summary follows:

“External biometrics have many applications in ornithology, and study skins are a major source of these measurements. However, measurements can be imprecise, and skins tend to shrink when they dry — two problems rarely investigated for petrels (family: Procellariidae). This study examined measurement error and shrinkage for 15 biometrics, using Short-tailed Shearwater Puffinus tenuirostris as the subject species. Random measurement error, defined as the variability of repeated measurements of a particular character taken on the same individual relative to its variability among individuals in a particular group, ranged from 0.3% for head plus bill length in dry specimens to 36% for tarsus width in freshly dead birds. Shrinkage of skin specimens stabilised within 2–5 months after preparation. Average fresh-dry shrinkage ranged from 0.2% for head plus bill to 12% for tarsus height. A new method was used to estimate shrinkage variability among individuals. “Shrinkage variation,” defined as the proportion of unexplained variance (1 – r2) in the correlation between paired fresh and dry measurements of a particular character after correcting for measurement error, ranged from 0% for wing chord to 33% for bill base width. More robust biometrics from this study were measurements of large, inflexible characters with well-defined measurement “landmarks.”

Short-tailed Shearwater, photograph by Mark Carey

Reference:

Totterman, S.L. 2016. Random measurement error and specimen shrinkage in Short-tailed Shearwaters Puffinus tenuirostris. Marine Ornithology 44: 11-20.

John Cooper, ACAP Information Officer, 08 March 2016

The Agreement on the
Conservation of Albatrosses and Petrels

ACAP is a multilateral agreement which seeks to conserve listed albatrosses, petrels and shearwaters by coordinating international activity to mitigate known threats to their populations.

About ACAP

ACAP Secretariat

119 Macquarie St
Hobart TAS 7000
Australia

Email: secretariat@acap.aq
Tel: +61 3 6165 6674