Fighter-pilot Parents Dataset

These data were collected to test parental investment theory's predictions that parents should defend offspring based on offspring survival and recruitment potential and that future reproductive opportunities should impact decisions about the costs and benefits of defending current offspring. We studied eastern bluebirds (Sialia sialis) and tree swallows (Tachycineta bicolor), two species with similar nest defense behaviors and breeding habitat preferences, that nevertheless differ in their within-season re-nesting potential. We collected data on three nest defense behaviors (diving, alarm calling, and beak clicking), as well as and offspring age, number, weight and size. We elicited defensive behavior via human visits to the nest box at all stages of nesting over five consecutive breeding seasons Nestling weight and size were also measured over three of these breeding seasons. All three defensive behaviors were strongly correlated with each other, so we focused our analysis on dives, as we were able to measure this behavior as a count rather than as presence or absence only as we did for beak clicks and alarm calls. Both species increased diving as nests aged. Tree swallows dived more than bluebirds in all stages in accordance with our prediction that the species with the lower re-nesting potential would invest more in their current nest. However, we found no association between parental defense and nestling quality or brood size.