Breaking bonds: maternal and offspring state shape constraint-based brood adoption in a seaduck

The adaptiveness of adoption for donors, recipients, and offspring remains unsettled despite long-standing interest. Using decade-long data on individually marked female and duckling common eiders (Somateria mollissima), displaying frequent alloparenting, we examined factors influencing the likelihood of females donating young and ducklings being adopted. We explored how donor traits, including maternal body condition, relative head size (a proxy of relative brain size), and relative hatching date, and offspring characteristics such as body condition relative to siblings, affect these processes. At least one offspring was permanently adopted in 34.7% of brood observations. Females in better body condition and larger relative head size were less likely to donate offspring, while the likelihood of offspring transfer was higher in larger natal broods. The odds of offspring donation peaked just before the population’s hatching peak, suggesting that recipient availability influences adoption..., , # Breaking bonds: maternal and offspring state shape constraint-based brood adoption in a seaduck

Dryad DOI: https://doi.org/10.5061/dryad.d51c5b0hb

**Article title:** Breaking bonds: maternal and offspring states relate to constraint-based brood donation in a seaduck\
**Journal:** Behavioral Ecology\
**Manuscript ID:** BEHECO-2025-0052.R2\
**Authors:** Markus Öst; Benjamin Steele; Kim Jaatinen\
**Corresponding author:** Markus Öst ([[e-mail]](mailto:[e-mail]))

## Dataset overview

This repository contains the raw data underlying two logistic regression analyses reported in the manuscript:

1. **Female-level analysis** — factors associated with whether a female was a *donor* (lost at least one duckling to another brood) vs. a *reference* (no permanent loss).\
**File:** `Data1_BEHECO-2025-0052_clean.csv` (cleaned, standardized variable names)
2. **Duckling-level analysis** — factors associated with whether an individual duckling was *adopted* into another brood vs...,