Ardea
Official journal of the Netherlands Ornithologists' Union

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Sasvari L. & Hegyi Z. (2001) Condition-dependent parental effort and reproductive performance in the White Stork Ciconia ciconia. ARDEA 89 (2): 281-291
Relationships between the parental quality and reproductive performance have been studied in many birds, but not in Ciconiiformes so far. We hypothesised that parental condition of White Storks Ciconia ciconia affects both parental care and breeding success. To examine our hypothesis we assessed body mass of White Stork parents and their offspring and recorded breeding performance and parental activity in Hungary during 1992-97. Sex-related differences in parental care were found: females incubated longer than males, males compensated for reduced incubation by females, males delivered more food than females. Condition-related differences in parental effort were found, with heavier females laying more eggs and incubating longer than lighter females. Heavy males and females delivered more food to their offspring than light males and females. Parental condition was positively correlated to clutch size and provisioning rate (and therefore the survival of last hatched chicks to fledge), but hatching success was not related. Light parents raised small broods, but with chicks of relatively high body mass while heavy parents raised large broods of lighter chicks. In years with many cold days during the breeding period, White Storks produced fewer but heavier offspring than in mild years. Body mass of parents increased during the period of chick provisioning, suggesting that parents favour their own future survival in that period


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