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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.

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.

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.

This dataset contains ecological and behavioral data from 12 recording sessions of Eastern Bluebird (Sialia sialis) young from a wild population in Virginia, USA. Data were collected on an ad libitum basis from May to July 2025. The begging durations and rates in the presence and absence of parents of given nests are recorded, as are the average acoustic parameters for each type of begging in each trial. Environmental and ecological data, such as weather, number of nestlings, etc. are recorded as well. The dataset supports analyses of patterns in parent-absent begging, structural differences between parent-absent and parent-present begging, the consequences of parent-absent begging, and more.

This dataset contains ecological and behavioral data from 12 recording sessions of Eastern Bluebird (Sialia sialis) young from a wild population in Virginia, USA. Data were collected on an ad libitum basis from May to July 2025. The begging durations and rates in the presence and absence of parents of given nests are recorded, as are the average acoustic parameters for each type of begging in each trial. Environmental and ecological data, such as weather, number of nestlings, etc. are recorded as well. The dataset supports analyses of patterns in parent-absent begging, structural differences between parent-absent and parent-present begging, the consequences of parent-absent begging, and more.