Abstract:

We characterized the reproductive effort of great tits (Parus major) feeding their nestlings by a food allocation index and analised its within- and between-individual, day to day variations with automated weighing of their nests under natural conditions (Tóth et al. 1991). We selected eight nests by random sampling from the nests weighted automatically over the feeding period at the nestbox site of the Biological Station of the Eötvös University within 1993-2003. The broods differ in a great extent in the profiles of the visit rate, mean prey mass and nestling provisioning. However, neither the average visit number per day nor the mean prey mass of the broods changes significantly while the daily amount of food per nestling slightly and significantly increases with the age of the nestlings. The allocation index does not differ significantly between the observed periods. The parent birds eat 29% of the collected food at least and give 71 % to the nestlings while the amount of the collected food varies in a wide range. In agreement with the model of (van Noordwijk & de Jong 1986) this leads to positive relation between the amount of food eaten by parents and given to the nestlings.