Comparison of geometric morphometric outline methods in the discrimination of age-related differences in feather shape

Table 1 Repeated measures variance under different measurement protocols using a single feather

Data acquisition	Data processing	Variance	95% confidence interval for variance
Automated	Bending energy	0.000594	0.000287 – 0.000780
Curve tracing	Bending energy	0.000213	0.000107 – 0.000295
Fan	Bending energy	0.000114	0.000057 – 0.000144
Automated	Perpendicular projection	0.000046	0.000027 – 0.000053
Curve tracing	Perpendicular projection	0.000011	0.000008 – 0.000011
Fan	Perpendicular projection	0.000009	0.000007 – 0.000009

Each protocol used 82 points around the periphery of the feather. A single feather was digitized 10 times. The confidence interval was determined using bootstrap resampling with replacement. The bending energy minimization always produced higher variance estimates than the perpendicular projection method.

ISSN: 1742-9994