This study examined possible associations between
allozymic variation in metabolic enzymes and social
dominance or survival in a large free-living population
of wintering White-throated Sparrows (Zonotrichia
albicollis). Electrophoresis of 15 enzymes
resolved from muscle biopsies from 173 sparrows revealed
nine enzymes with some variation. Two of these
(PGM and 6-PGD) showed substantial variation, with the
frequency of the common allele below 0.9. During
two seasons dominance interactions among the biopsied
birds were observed at three feeding stations.
There was no association between social dominance (percentage of
opponents dominated) and genotype at the two most variable loci
or overall proportion of heterozygotes at either the two most
variable loci or the seven most consistently scored loci.
Older birds were more likely than expected to be
heterozygous at both the PGM and 6-PGD loci, but heterozygotes
did not return more frequently than homozygotes in subsequent
years. Although we cannot exclude a weak association of
dominance and isozyme variability, we can conclude that social
dominance during winter lacks any strong relationship with
variation at loci for metabolic enzymes.