14Incubation by both parents is the most common form of care for eggs. Although the involvement of 15 the two parents may vary dramatically between and within pairs, as well as over the day and 16breeding season, detailed description of this variation (especially in species with variable male 17 contribution to incubation) is rare. Here, we continuously video-monitored 113 nests of Northern 18Lapwing Vanellus vanellus over the breeding season to reveal the diversity of incubation rhythms 19 and parental involvement. We found great between-nest variation in the overall nest attendance (68 20 -94%; median = 87%) and in how much males incubated (0 -37%; median = 13%). Notably, the less 21 the males incubated, the lower was the overall nest attendance, even though females partially 22 compensated for the males' decrease. Overall, incubation rhythms changed little over the season 23 and incubation period. However, as nights shorten with the progressing breeding season, the female 24 longest night incubation bout shortened too. Essentially, nest attendance was highest, incubation 25 bouts longest, exchange gaps shortest and male involvement lowest during the night. Also, males 26 tended to incubate the most after sunrise and before sunset. To conclude, we revealed strong 27 circadian rhythms and remarkable between nest differences in Northern Lapwing incubation 28 (especially in male involvement), yet despite seasonal environmental trends (e.g. increasing 29 temperature) Lapwing incubation rhythms remained relatively stable over the season and incubation 30 period. 31