PARENTAL AGE AND REPRODUCTION IN THE MARSH TIT PARUS-PALUSTRIS

In the Marsh Tit Parus palustris, breeding performance improved with t he age of both the male and the female parent-older birds produced lar ger clutches earlier in the season. The effect of male age, however, w as mainly due to a positive association with the age of the female. Wh en the effect of laying date was accounted for, there was no additiona l effect of female age on clutch-size. However, pairs with previous br eeding experience laid larger clutches than newly formed pairs of the same age. There was some evidence that young females that laid late in the season were less likely to survive to breed again, leading to an age effect on reproductive performance. There was no evidence that ind ividual birds laid earlier or produced larger clutches when they becam e older.