Fig. 4
From: Using skin temperature and activity profiles to assign chronotype in birds
Determination of onset and offset of diel change in skin temperature. Bird-specific onset (A) and offset (B) estimates are calculated by four methods (different colours) for eight Great Tits (female (F) and male (M)) kept in outdoor aviaries during winter. Mean (± SEM) chronotype estimates (in numeric daytime hours) and information on colour coding are given for each method in the inlay. Each panel represents skin temperatures of one Great Tit with mean (black dots) ± standard errors (grey bars) per 10-min bin, the fitted sinusoidal curve (blue, based on 3-harmonic smoothing), and the skin temperature chronotype estimates as vertical lines. Daylight phases are indicated in yellow (sunrise–sunset)