Abstract
BackgroundIn high latitude grassland habitats, altricial nestlings hatching in open-cup nests early in the breeding season must cope with cold temperature challenges. Thyroid hormones (triiodothyronine, T3 and thyroxine, T4) and corticosterone play a crucial role in avian thermoregulation response to cold. Investigating the endocrine response of altricial nestlings to temperature variation is important for understanding the adaptive mechanisms of individual variation in the timing of breeding in birds.MethodsWe compared nest temperature, ambient temperature, body temperature, plasma T3, T4 and corticosterone levels in Asian Short-toed Lark (Alaudala cheleensis) nestlings hatching in the early-, middle-, and late-stages of the breeding season in Hulunbuir grassland, northeast China.ResultsMean nest temperature in the early-, middle- and late-stage groups was − 1.85, 3.81 and 10.23 °C, respectively, for the 3-day-old nestlings, and 6.83, 10.41 and 11.81 °C, respectively, for the 6-day-old nestlings. The nest temperature significantly correlated with body temperature, plasma T3, T4 and corticosterone concentrations of nestlings. Body temperature of 3-day-old nestlings in the early and middle groups was significantly lower than that of the late group, but there was no significant difference between the nestlings in the early and middle groups. The T4 and T3 concentrations and the ratio of T3/T4 of both 3- and 6-day-old nestlings in the early-stage group were significantly higher compared to the middle and late groups. The corticosterone levels of 3-day-old nestlings were significantly higher in the early-stage group compared to the middle- and late-stage groups.ConclusionNestlings hatching early responded to cold temperature by increasing thyroid hormones and corticosterone levels even in the early days of post hatching development when the endothermy has not been established. These hormones may play a physiological role in neonatal nestlings coping with cold temperature challenges.
Highlights
In high latitude grassland habitats, altricial nestlings hatching in open-cup nests early in the breeding season must cope with cold temperature challenges
Nest temperature and ambient temperature The nest temperature for 3- and 6-day-old nestlings was significantly different between hatch groups (3-day-old: one-way ANOVA, F2,38 = 23.06, P < 0.001; 6-day-old: oneway ANOVA, F2,45 = 5.47, P < 0.01)
Body temperature of nestlings The Linear mixed model result for body temperature indicated that nest temperature, age, hatch stage, and the interactions between these factors, significantly influenced the body temperature of nestlings (Table 1)
Summary
In high latitude grassland habitats, altricial nestlings hatching in open-cup nests early in the breeding season must cope with cold temperature challenges. Thyroid hormones (triiodothyronine, T3 and thyroxine, T4) and corticosterone play a crucial role in avian thermoregulation response to cold. Investigating the endocrine response of altricial nestlings to temperature variation is important for understanding the adaptive mechanisms of individual variation in the timing of breeding in birds. Shang et al Avian Res (2021) 12:55 of breeding early is that nestlings must deal with cold temperatures (Rotics et al 2018) This is the case for altricial nestlings raised in open-cup nests in exposed high latitude locations (MacDonald et al 2013). Understanding the adaptive mechanisms of individual variation in the breeding time of birds inhabiting highly seasonal environments requires determining how nestlings respond to cold ambient temperatures in early spring. Recent studies in Blue Tits (Cyanistes caeruleus) suggest there may be an association between baseline corticosterone, peripheral body temperature, and gradual changes in temperature over winter and summer (Jerem et al 2018)
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