LOW-FREQUENCY OF EXTRA-PAIR FERTILIZATIONS IN THE GREAT TIT PARUS-MAJOR REVEALED BY DNA-FINGERPRINTING

Multilocus DNA fingerprinting was used to estimate the frequency of ex tra-pair fertilizations in a low density, island population of Great T its Parus major. A total of 69 pairs and 516 offspring from 82 breedin g attempts were examined. Only 18 offspring (3.5%) in seven different nests were not fathered by the attending male. The sample included one brood in which all nine chicks were fathered by an extra-pair male. O ne chick from a nest of eight was the result of intra-specific brood p arasitism. Three chicks from a brood of nine could be matched with the male but not with the female. Observations at this nestbox suggested that mate switching had occurred during the laying period. The percent age of extra-pair fertilizations did not differ between first clutches and (experimentally induced) replacement clutches. Females mated to s mall males were more likely to have extra-pair young in the nest. Beca use both extra-pair paternity and intraspecific brood parasitism are r are in this population, a reliable measure of reproductive success can be obtained by counting the number of offspring.