| Summary: | In birds, incubation by both parents is a common form of care for eggs. Although the involvement ofthe two parents may vary dramatically between and within pairs, as well as over the course of the dayand breeding season, detailed descriptions of this variation are rare, especially in species with variablemale contributions to care. Here, we continuously video-monitored 113 nests of Northern Lapwings Vanellus vanellus to reveal the diversity of incubation rhythms and parental involvement, as well as their daily and seasonal variation. We found great between-nest variation in the overall nest attendance (68–94%; median = 87%) and in how much males attended their nests (0–37%; median = 13%).Notably, the less the males attended their nests, the lower was the overall nest attendance, eventhough females partially compensated for the males’ decrease. Also, despite seasonal environmentaltrends (e.g. increasing temperature), incubation rhythms changed little over the season and 27-dayincubation period. However, as nights shortened with the progressing breeding season, the longestnight incubation bout of females shortened too. Importantly, within the 24h-day, nest attendance washighest, incubation bouts longest, exchange gaps shortest and male involvement lowest during thenight. Moreover, just after sunrise and before sunset males attended the nest the most. To conclude,we confirm substantial between nest differences in Lapwing male nest attendance, reveal how suchdifferences relates to variation in incubation rhythms, and describe strong circadian incubation rhythmsmodulated by sunrise and sunset.
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