Typical habitats are dry vegetated and barren habitats in the Arctic, such as windswept ridges, slopes or plateaus. Nests are usually placed in a small patch of vegetation within about 500 m (1,640 ft) of a pond, wetland or waterbody. Both subspecies of knots lay three or four eggs in the last half of June and the chicks hatch in mid- July. Nests are extremely hard to find because knots are well camouflaged and do not leave the nest, even when approached.
To prepare for migration to their breeding grounds, Red Knots increase the size of the parts of their body used for flying (heart and flight muscles) and decrease the size of the parts not used for flight (digestive system). Once they arrive on their breeding grounds, their reproductive organs increase in size and their heart and flight muscles decrease to normal size.