PATERNITY AND PATERNITY ASSURANCE BEHAVIOR IN THE BLUETHROAT, LUSCINIA-S SVECICA

Genetic parentage was examined in the territorial and predominantly mo nogamous bluethroat, by means of multilocus DNA fingerprinting. Thirty -five per cent (11/31) of nests contained one or more offspring sired by extra-pair males, in total 20% (30/150) of all offspring. The frequ ency of extra-pair paternity was similar in the two study years. All o ffspring were genetically related to their putative mother, thus no ev idence for intraspecific brood parasitism was found. Extra-pair offspr ing were not randomly distributed, but were clustered in certain brood s, in which on average 54% of the young were sired by extra-pair males . Ten copulations were seen, one of which was an extra-pair copulation . Males guarded their mate intensely around the start of egg laying, s taying within 1 m of her for more than 60% of the time. The male typic ally followed the female, and not vice versa. Henck, mate guarding was not a cooperative behaviour of the two sexes. Male singing activity d eclined gradually during the breeding season without reaching a peak d uring the females' fertile period. Male bluethroats thus apparently us e mate guarding and not song as their primary paternity guard. For a s ubset of pairs (N=8) the observed behaviour could be related to patern ity. These data indicated that, during the fertile period, there were more intrusions in territories with extra-pair offspring than in terri tories with only legitimate offspring. There was also a non-significan t tendency for males with full paternity in their nest to mate guard m ore intensely than males with reduced paternity. (C) 1996 The Associat ion for the Study of Animal Behaviour