Data from: Prebreeding populations and the importance of life history for conserving the world’s imperiled seabirds
Abstract
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., breeding age) shape both obstacles to, and opportunities for, successful conservation.
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 AviList species list (https://www.avilist.org/checklist/v2025/)
Columns:
- Taxon: Scientific binomial
- Sequence: Numeric order (following phylogenetic conventions)
- Order: Taxonomic order
- Family: Taxonomic family
- Genus: Genus name only
- Species: Species name only
- English_Name_AviList: One common name in English
- IUCN_Red_List_Category: Species category from the International Union for Conservation of Nature (LC=Least Concern, NT=Near Threatened, VU=Vulnerable, EN=Endangered, CR=Critically endangered, NE=Not evaluated)
- AvibaseID: The Avibase code associated with this taxon concept
- Age_First_Breeding: The age, in years, when most individuals begin reproducing
- Breeding_Propensity: The probability that a female attempts to nest each year
- Missing values were calculated based on the arithmetic mean of other species in the same taxonomic family; these are labeled with a "(CALCULATED)" prefix.
- Reproductive_Success: The number of female fledglings per nesting attempt
- Juvenile_Survival: Survival rate from fledging to 12 months old
- Subadult_Survival: Annual survival rate from 12 months old to age at first breeding
- Adult_Survival: Annual survival rate from age at first breeding until death
- Source: Reference DOI (BOTW = Cornell's Birds of the World Encyclopedia, https://birdsoftheworld.org/)
- New_Assumptions: Key assumptions applied to underlying reported parameters (e.g., annualized a survival rate from a multi-year survivorship rate, separated a subadult and adult survival rate where they were estimated as one parameter in the original source)
- Notes: Explanation and justification of individual values
Compilation, synthesis, and curation of previous-published demographic data.