For successful breeding, good timing is of the utmost importance for birds inhabiting seasonal environments. Seasonal declines in reproductive success have been well documented in birds (e.g. Perrins 1970; Verhulst et al. 1995) and shown to be causally related to the timing of breeding (e.g. Verhulst et al. 1995; Brinkhof and Cave 1997). For arctic breeders the window in which breeding can take place is even narrower. Therefore, the capacity of migratory birds to fit both their breeding season and preparations for return migration to southern latitudes into the short arctic summer has provided a long-standing riddle. Because of this constraint and the apparent lack of feeding opportunity on the breeding grounds upon arrival, many researchers have deemed the importance of postmigratory residual body stores for successful breeding (e.g. Ryder 1970; Ankney and MacInnes 1978; Drent and Daan 1980; Ebbinge et al. 1982; Davidson and Evans 1988; Sandberg and Moore 1996). The residual stores potentially enable a rapid initiation of egglaying, thereby shortening the breeding season. In 1980, Drent and Daan wrote a classic paper in which they introduced the concepts of “capital” and “income” breeding; The Prudent Parents of the Arctic probably bringing along stores (capital) from the wintering grounds or flyways to the breeding destination, as contrasted by income breeders, which produce eggs from nutrients obtained directly from their local diet on the breeding grounds.