Nests are placed at varying heights, anywhere from one meter to 15 meters above the ground. Females construct a nest composed predominately of strands of yellow birch bark with a lining of animal hair, rootlets or lichens. After nest completion, females will lay an average of three to four eggs, which they begin incubating when the second to last egg is laid. Unlike many species of migratory birds which raise two successive sets of young, i.e., broods, during a single breeding season, redstarts call it quits after successfully raising a single brood. However, if the first nesting attempt fails, for example, if a predator eats the eggs or young, redstarts will continue trying to raise a successful brood, as long as environmental conditions remain favorable.
Male redstarts can be polygynous and polyterritorial.
That is to say, males can sometimes be paired with two females, but rather than having both females on the same territory they maintain two separate and disjunct territories. You might be wondering how one male can balance two females and two nests at once, especially considering that both parents feed the young. Well, the trick lies in the fact that the nests are not entirely synchronous. Males typically do not start advertising for a second female until the first and primary female has started incubating. That way if the male is successful in attracting a second female, he minimizes the overlap of parental care duties between the two nests and can fledge significantly more young.