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Few details of Red Knots (Calidris canutus) breeding biology are known because of birds of this species have secretive behaviour on their breeding ground. Results obtained from recordings of light-level geolocators applied to three Red Knot males (C. c. rogersi subspecies) in southern Chukotka, Far Eastern Russia, have revealed a possibility of getting important information not only about bird migration, but also about some details of birds behaviour and schedule on their breeding grounds. Daily dark period (= nightshade) lasts for about 4 hours at this latitude (N 62,5 deg) in summer, but both typical incubation and off-duty bouts last for 6-12 hours in Red Knots, thus making it possible to increase sample sizes for measurements of these parameters if their start or termination does not fall into a nightshade period. Incubation of a bird on its nest as indicated by its geolocator has been confirmed by direct observations on one nest. It turned out that geolocator signal daily median is the best matching indicator for incubation period estimation. However, this incubation period differs from a traditional one by presumable inclusion of at lest a day of incomplete clutch incubation and half a day of hatched chicks warming in the nest. Involvement of females in incubation seems to be shorter, but such information is missing. Other parameters deriving from geolocators data are arrival and departure dates, and post-nesting periods that birds spend on their breeding grounds. The latter turned to be longer in the population under study as compared to C. c. rufa from high-Arctic Canada. Complete absence of geolocators contact with salt water while birds stay on the breeding grounds is surprising.