Dissociation of circadian activity and singing behavior from gene expression rhythms in the hypothalamus, song control nuclei and cerebellum in diurnal zebra finches

Nocturnal singing by diurnal birds in Afrotropical highlands

“…Some bird species adapt their daily rhythm to these conditions and are continuously active or demonstrate 'free-running', individually specific activity cycles (Steiger et al 2013). Experimental studies on zebra finches also confirmed that periodicity in light-dark conditions induces rhythmic cycles of singing (singing during 12 h in the light, no singing during 12 h in the dark), while conditions of continuous light cause a decline in daily patterns, even resulting in completely arrhythmic singing activity (e.g., singing scattered across the 24-h period) (Prabhat et al 2019). Thus, tropical birds' habit of staying quiet at night and singing by day is likely to be a response to their rhythmic and stable light-dark conditions, while the more-arrhythmic singing activity in some bird species in temperate zones may suggest that these species adapt their circadian clock to seasonal changes in day and night.…”

“…Close to the equator, day and night are almost equal in duration and stable throughout the year. Such strongly periodical light-dark conditions should induce rhythmic daily patterns of physiological and behavioural processes (Yamada et al 1988), including singing activity (Prabhat et al 2019). In temperate zones, even over the length of a short breeding season (2-4 months), the duration of day increases noticeably, with day-time much longer than night, and in the case of the far north or south, no night at all.…”

Effects of Night Illumination on Behavior, Body Mass and Learning in Male Zebra Finches

“…The significance of the cosinor regression was calculated by using the number of samples, R 2 values and numbers of predictors (https://www.danielsoper.com/statcalc/calculator.aspx?id=15; Soper 2013, 29 August 2021). An extra sum of squares F-test also determined significant differences in the rhythm waveform parameters (i.e., mesor, amplitude and acrophase) of daily behaviors between light conditions, as reported in several publications [13,20]. The alpha was set at 0.05 for statistical significance.…”

“…Pearson and Spearman correlation coefficient was calculated to show correlation between two variables (colour learning and sleep). We tested 24 h rhythmicity in the daily behaviors by unimodal non-linear cosinor regression analysis (y = A + [B.cos (2π (x − C)/24)]), where A, B, and C denote the mesor (mean 24 h behavioral values), amplitude (maximum change in behavior levels relative to the mesor) and acrophase (the estimated time of peak of behavior) of 24 h rhythm, respectively (Prabhat et al, 2019) [20]. The significance of the cosinor regression was calculated by using the number of samples, R 2 values and numbers of predictors (https://www.danielsoper.com/statcalc/calculator.aspx?id=15; Soper 2013, 29 August 2021).…”

“…Specifically, increased light at night disrupted daily rhythm with loss of nocturnal peak in melatonin secretion in the Indian weaver bird (Ploceus philippinus; [15]), great tits (Parus major; [8][9][10][11][12][13][14]16]), Indian house crows (Corvus splendens; [14]) and female zebra finches (Taeniopygia guttata; [17,18]). Bright light at night (constant light) and removal of pineal gland exposure decayed daily rhythms in singing and activity behaviors in zebra finches [13,[19][20][21] and alters the perception of day length and affects the underlying physiology in Indian Weaver bird [22]. The light at night induces "eating at a wrong time" in both mammals and birds.…”