Prebreeding populations and the importance of life history for conserving imperiled seabirds

Seabird conservation often focuses on nestlings and breeding adults. Yet imperiled seabird populations also contain prebreeders, including juveniles and subadults, that wait several years before breeding at colonies. We use previously-published data on reproductive and survival rates for 90 species to quantify the conservation relevance of prebreeding seabirds. We find, first, that prebreeders average about half of seabird populations (median 48.1%, range 7.6–70.0%). Second, while seabird population growth is much more sensitive to adult survival than prebreeder survival, human-driven changes may shift the importance of prebreeders for future population stability. Third, lowering the breeding age is a potentially useful, but underexplored, route to increasing population growth. Managing prebreeders could thus play a key role in protecting seabirds. This task may require answering fundamental questions about the behavior of young birds. Broadly, we suggest that life history traits (e.g.,..., Compilation, synthesis, and curation of previous-published demographic data., , # Data from: Prebreeding populations and the importance of life history for conserving imperiled seabirds

[https://doi.org/10.5061/dryad.dfn2z35cm](https://doi.org/10.5061/dryad.dfn2z35cm)

## Files

All data for this study are available in data.csv

Values are compiled from previously-published reports, which are directly cited within the file. We also explain the derivation of specific demographic values wherever needed.

All code for this study are available in analysis.r (Zenodo - Software)

Running this R script will replicate all results, figures, and output reports. First, install the necessary R packages (tidyverse, patchwork). Second, move the data.csv file to a Data/ directory. Third, create an Output/ directory. Then, simply run the script.

### Data variables (data.csv)

**Description:** Each row is a seabird species, with taxonomic information, summarized demographic values, and the sources and explanations of those values. All taxonomic information follows the 2025 AviLi..., ,