The relationship between phenological traits and brood size of the white stork Ciconia ciconia in western Poland

Changes in the spring arrival dates of migrant birds have been reported from a range of locations and many authors have focused on long-term trends and their relationship to temperature and other climatic events. However, there may be consequences (costs) for changes in arrival dates which long-lived birds may have to repay in the future. In this paper we take the opportunity provided by a detailed monitoring scheme to examine several features of the timing of arrival in relation to chick production of white storks Ciconia ciconia in Poland during the period 1983–2003. Longer occupied nests were associated with greater productivity than shorter occupied ones. Early arriving pairs were more productive than later ones. Individual birds and the whole population could achieve greater productivity by earlier arrival. However, high chick production in one year tended to be followed by a slightly lower productivity and delayed arrival in the following year. Hence, the cost of early arrival at breeding sites may have to be paid for in the following, rather than in the current, year.