Several different selective pressures have been suggested to explain an intense competition for early return to breeding grounds in birds. In this study we hypothesized that shortening day length during summer months may constitute additional selective force acting towards early breeding in avian species with long parental care. To test this hypothesis, we studied time budget and foraging activities of early-nesting and late-nesting white storks Ciconia ciconia from the Central-European population. We found that duration and distance of foraging trips increased significantly over the course of the reproductive season. The relative frequency of foraging trips increased at the expense of other activities, such as resting, plumage maintenance, and nest maintenance. Mean daily foraging duration increased with increasing day length in the early part of the season, with 0.68 h of foraging per individual per 13.16 h of day length in mid-April increasing to 7.42 h of foraging per individual during solstice (16.61 h of day length). Afterwards, mean foraging duration continued increasing in spite of decreasing day length, reaching 11.63 h of foraging per individual per 14.92 h of day length at the end of the season in mid-August, when storks were forced to continue foraging after sunset in order to meet energy requirements of fledglings. The results suggest that shortening day length during summer months may constitute a serious time constraint on food delivery rates to offspring for late-breeding pairs of white stork.Keywords Ciconia ciconia Á Foraging Á Photoperiod Á Timing of breeding Á White stork Zusammenfassung Kü rzere Tage sind ein bisher unbekannter Selektionsdruck fü r frü hen Brutbeginn in einer Vogelart mit langer elterlicher Fü rsorge Verschiedene Selektionsfaktoren wurden bisher herangezogen zu erklären, warum Vögel so intensiv konkurrieren möglichst früh im Brutgebiet anzukommen. In dieser Studie untersuchten wir die Hypothese, dass kürzere Tage während der Sommermonate in Arten mit langer Elternfürsorge einen weiteren Selektionsfaktor darstellen, der frühen Brutbeginn begünstigt. Um diese Hypothese zu testen verglichen wir die Zeiteinteilung und Dauer der Nahrungssuche bei früh und spät nistenden Weißstörchen Ciconia ciconia in einer zentraleuropäischen Population. Die Dauer und Entfernung von Nahrungsflügen nahm im Laufe der Brutsaison signifikant zu. Die relative Häufigkeit von Nahrungsflügen stieg ebenfalls an, was auf Kosten anderer Aktivitäten wie Rast, Gefiederpflege und Nestpflege geschah.