Offspring thermal demands and parental brooding efficiency differ for precocial birds living in contrasting climates

BackgroundChicks of precocial birds hatch well-developed and can search actively for food but their homeothermy develops gradually during growth. This makes them dependent on heat provided by parents (brooding), which is then traded off against other activities, mainly foraging. Although brooding has been documented in many precocial birds, little is known about the differences in the amount and efficiency of brooding care, brooding diel rhythmicity, and impact on the chick's growth, particularly between species living in different climatic conditions.ResultsWe used multisensory dataloggers to evaluate brooding patterns in two congeneric species inhabiting contrasting climate zones: temperate Northern lapwing (Vanellus vanellus) and desert Red-wattled lapwing (Vanellus indicus). In accordance with our expectation, the adult desert lapwings brooded the chicks slightly less compared to the adult temperate lapwings. However, the desert lapwings brooded their chicks in higher ambient temperatures and less efficiently (i.e. they could not reach the same brooding temperature as the temperate lapwings), which are new and hitherto unknown brooding patterns in precocial birds. In both species, night brooding prevailed even during warm nights, suggesting a general brooding rule among birds. Although the high rates of brooding can reduce the time spent by foraging, we found no negative effect of the high brooding rate on the growth rate in either species.ConclusionsOur data suggest that the chicks of species breeding in colder climates may reduce their thermal demands, while their parents may increase the efficiency of parental brooding care. More research is however needed to confirm this as a rule across species.

Automated summary

Two congeneric species, the Northern lapwing and the Red-wattled lapwing, which inhabit different climate zones, exhibit differences in brooding patterns and efficiency. Higher brooding rates do not have a negative effect on the growth rate of the chicks.