Time spent in sleep-wakefulness states and mean bout durations correlate with PCSK2 expression in feather follicles. Time spent in (a) wakefulness, (b) non-REM sleep, and (c) REM sleep, mean bout durations for (d) wakefulness, (e) non-REM sleep, and (f) REM sleep and (g) mean REM sleep latency (n = 61). The following correlations with PCSK2 expression were statistically significant: time spent in non-REM sleep (Pearson’s correlation: r = 0.30, p = 0.019) and duration of bouts of non-REM sleep (r = 0.29, p = 0.023; see also analysis in Table 1 where this relationship is only a trend), time spent in REM sleep (r = -0.36, p = 0.005), and duration of bouts of REM sleep (r = -0.35, p = 0.006). None of the other variables correlated significantly with PCSK2 expression (p-values > 0.23). Similar results were obtained when we calculated mean values for each nest.