PATERNAL INVESTMENT INVERSELY RELATED TO DEGREE OF EXTRA-PAIR PATERNITY IN THE REED BUNTING

EXTRA-PAIR copulations, in which a female copulates with a male other than her mate, are known to occur in many bird species(1). Here we stu dy a wild population of reed buntings, Emberiza schoeniclus, using sin gle-locus DNA fingerprinting(2,3) and find an exceptionally high propo rtion of extra-pair paternity that accounts for 55% (118/216) of young and 86% (50/58) of nests. Twelve pairs each raised two broods in a si ngle season in which the proportion of extra-pair young differed betwe en the two broods. A highly significant relationship between a male's parental investment and his degree of paternity was revealed by a comp arison between the first and second brood of each pair, with more pate rnal care usually being provided at the nest that contained a lower pr oportion of extra-pair young. We propose that males can assess their l ikelihood of paternity and adjust their nestling provisioning rates ac cordingly.