Day–night cycle influences the division of incubation in the Hooded Dotterel (Thinornis cucullatus)

Abstract

In species with biparental care, diel patterns in male and female incubation arise due to the differential costs and benefits of incubation. This pattern should be less obvious or absent in species where both sexes stand to benefit significantly from investing in incubation (i.e. in monogamous species with high paternity certainty), in temperate climates and in sexually monomorphic species where sexes probably experience similar physiological costs and risks of detection by predators. Despite no obvious size or colour differences between male and female Hooded Dotterel Thinornis cucullatus, males incubated significantly more at night (59% of the time), and less during the day (43% of the time). We show that despite Hooded Dotterel being sexually monomorphic, long‐lived with probably high paternity certainty, incubation is not shared equitably, with a bias towards male nocturnal incubation.

The causes and implications of sex role diversity in shorebird breeding systems

“…For example, incubation by brighter male Rufous-chested Dotterels Charadrius modestus is biased towards the day, whereas the duller females incubate at night (St Clair et al 2010). Similarly, male and female Hooded Dotterels Thinornis cucullatus are monomorphic, but males still incubate more at night (Ryeland et al 2022). Such differences indicate that other sex differences in the costs and benefits of care may shape diel sex roles in incubation, such as sex differences in the need to forage at the most efficient time of day (St Clair et al 2010, Bulla et al 2014.…”

“…Similarly, male and female Hooded Dotterels Thinornis cucullatus are monomorphic, but males still incubate more at night (Ryeland et al . 2022). Such differences indicate that other sex differences in the costs and benefits of care may shape diel sex roles in incubation, such as sex differences in the need to forage at the most efficient time of day (St Clair et al .…”