Data from: Age-dependent trajectories differ between within-pair and extra-pair paternity success

Reproductive success is associated with age in many taxa, increasing in
early life followed by reproductive senescence. In socially monogamous,
but genetically polygamous species, this generates the interesting
possibility of differential trajectories of within-pair and extra-pair
siring success with age in males. We investigate these relationships
simultaneously using within-individual analyses with 13 years of data from
an insular house sparrow (Passer domesticus) population. As expected, we
found that both within- and extra-pair paternity success increased with
age, followed by a senescence-like decline. However, the age trajectories
of within- and extra-pair paternity successes differed significantly, with
the extra-pair paternity success increasing faster, albeit
non-significantly so, in early life, and showing a delayed decline by 1.5
years on average later in life compared to within-pair paternity success.
These different trajectories indicate that the two alternative mating
tactics should have age-dependent payoffs. Males may partition their
reproductive effort between within- and extra-pair matings depending on
their current age in order to reap the maximal combined benefit from both
strategies. The interplay between these mating strategies and age-specific
mortality may explain the variation in rates of extra-pair paternity
observed within and between-species.