Kentish plovers Anarhynchus alexandrinus increase parental cooperation in variable environments

Environmental variability significantly influences parental care, likely because parental care can buffer nest survival against environmental variations, enabling those receiving greater parental care to tolerate a wider range of conditions. Under harsh conditions (e.g., high temperatures), this buffering effect may be reinforced through increased parental cooperation. Here, using data from a coastal and an inland site, we examined the effects of high ambient temperature (T_a) and wind, and their variability, on nest attendance and behavioural thermoregulation in Kentish plovers (Anarynchus alexandrinus). To quantify plover activity at their nests in relation to T_a, low-cost dataloggers were fully customised. A system was designed around a single board computer, connected to a webcam, a temperature sensor, and a clock module to synchronise timestamps when comparing results from dataloggers. In the Kentish plover, males typically incubate at night, whereas females incubate during the day; however, at elevated T_a, males also contribute to diurnal incubation. We found that at higher T_a, the plovers increased the frequency of heat-dissipating behaviours and switched incubation bouts between pair members more frequently. Wind speed additionally influenced the thermoregulatory behaviour of plovers, likely through convective cooling, thereby allowing longer periods of uniparental incubation. Furthermore, we show that at the same temperature, males exhibited higher nest attendance at the more variable inland site. Because this involvement exceeded that observed at the coastal site under equivalent temperatures, it may provide a safety margin against environmental variability. These findings support the hypothesis that environmental variability contributes to variations in parental cooperation during incubation.