(e) Statistics
Relative abundance ratios were calculated in Proteome Discoverer and the
data were both row and column (i.e., protein and sample) normalized to
an average value of 100. Data are shown as the mean ± SE. A studentt -test was used to find variation between feather
(δ2Hf), claw
(δ2Hc) hydrogen isotope ratios, and
physiological response variables (i.e., CPV, T, FS, and BM) measured in
two groups. We initially compared normalized abundances for each protein
between residents and migrants using standard two sample t -test,
followed by multiple correction test based on a sequential goodness of
fit (SGoF) metatest (Carvajal- Rodríguez, Uña-Álvarez, & Rolán-Álvarez,
2009). Because of small sample size, individual protein abundance
comparisons exhibit large sample variance, and small fold changes.
Stringent multiple testing correction methods to calculate false
discovery rate (FDR) for multiple repeated t -tests are often not
suitable for small sample size proteome experiments. In such condition a
liberal multiple testing correction methods SGoF metatest can be a
valuable approach for multitest adjustment. All statistical analyses
were conducted using R (version 3.2.0) or GraphPad Prism version 6, and
a p value <0.05 was considered significant.