Moonlight Duration and Intensity Favour Nocturnal Activity in a Diurnal Desert Bird

Animals that primarily use vision may benefit from moonlight to forage and communicate with conspecifics at night. In a previous study we found increased activity at full moon in a diurnal bird, the Canarian houbara bustard, Chlamydotis undulata fuertaventurae . Here, by analysing detailed records from loggers with an accelerometer (ACC), we investigate the timing and intensity of nocturnal display (vocalisations, visual display) and non‐display activity (foraging, preening) in both sexes and during the breeding and non‐breeding seasons, in relation to the time when the moon is visible at night and the extent of the illuminated lunar surface. Both sexes were much more active when the moon was visible (males spent, in 2018–2021, 7.68%–8.30% of their time foraging, 6.85%–7.03% preening and 4.48%–11.64% displaying; females spent 13.72% of their time foraging and 3.14% preening in 2021) than when the moon was hidden (males: 1.78%–2.73% foraging, 2.01%–3.23% preening and 0.91%–5.98% displaying; females: 5.75% foraging and 1.03% preening). Throughout the lunar cycle between new and full moon, the combined effects of a longer visible moon period and a larger illuminated lunar surface apparently contributed to an exponential increase in houbara activity. The increase remained even when controlling for moonlight duration, confirming a direct effect of moon illuminance. Running displays, the visual form of male display, were more frequent during full moon, when they always occurred during the visible moon period. At full moon, both display and non‐display activity rates were remarkably high, reaching about half of the values recorded during the daytime period of maximum activity (evening twilight for non‐display, morning twilight for display). Houbaras benefited from the moonlight just before morning twilight on waning moon to advance the onset of display that would normally occur during morning twilight. Similarly, they used moonlight just after evening twilight on waxing moon to prolong foraging activity until moonset. These results confirm that houbaras use moonlight to increase the time they can devote to feeding and reproductive activities.