Data for: General cognitive performance declines with female age and is negatively related to fledging success in a wild bird

Identifying the causes and fitness consequences of intraspecific variation
in cognitive performance is fundamental to understand how cognition
evolves. Selection may act on different cognitive traits separately or
jointly as part of the general cognitive performance of the individual. To
date, few studies have examined simultaneously whether individual
cognitive performance covaries across different cognitive tasks, the
relative importance of individual and social attributes in determining
cognitive variation, and its fitness consequences in the wild. Here, we
tested 38 wild southern pied babblers (Turdoides bicolor) on a cognitive
test battery targeting associative learning, reversal learning and
inhibitory control. We found that a single factor explained 59.5% of the
variation in individual cognitive performance across tasks, suggestive of
a general cognitive factor. General cognitive performance varied by age
and sex; declining with age in females but not males. Older females also
tended to produce a higher average number of fledglings per year compared
to younger females. Analysing over 10 years of breeding data, we found
that individuals with lower general cognitive performance produced more
fledglings per year. Collectively, our findings support the existence of a
trade-off between cognitive performance and reproductive success in a wild
bird.