Nest site choice: a potential pathway linking personality and reproductive success

• We study personality, nest site and reproductive success of chestnut thrushes.
• Boldness and activity are significantly repeatable across time.
• Bold females prefer to nest away from conspecific nests and human settlements.
• Nesting in low local breeding density produces more and lighter offspring.
• Nesting far away from human settlements and roads produces lighter offspring.

Animal personality has been linked to individual fitness across many taxa. However, the exact path by which personality translates into fitness is rarely identified. We tested whether nest site choice may serve as a potential pathway linking personality and reproductive success in a natural population of chestnut thrush, Turdus rubrocanus. Using path analysis, we found that human disturbance and choice of nest site with respect to nest density may both mediate the link between personality and reproductive success. Bolder females may choose nest sites with lower nest density, and the low nest density in turn may be responsible for a positive effect on nestling number, and have a negative effect on nestling mass. Bolder females may also prefer nest sites further from human settlements, resulting in a negative effect on nestling mass. Our findings provide rare exact mechanistic pathways by which boldness might be translated into reproductive success.