The influence of year, laying date, egg fertility and incubation, individual hen, hen age and mass and clutch size on maternal immunoglobulin Y concentration in captive Steller's and spectacled eider egg yolk

• Maternal IgY transfer was investigated in captive Steller's and spectacled eiders.
• Factors that influenced IgY transfer were determined.
• Year and individual hen influenced yolk IgY concentration in both species.
• Laying date was negatively correlated with IgY levels in Steller's eider eggs.
• Laying order was positively correlated with spectacled eider IgY concentration.

Steller's eiders and spectacled eiders are sea duck species whose populations have declined significantly and infectious diseases could influence offspring survival. Therefore, the maternal transfer of immunoglobulin Y (IgY) into yolk was investigated in captive Steller's and spectacled eiders during the 2007–2013 breeding seasons. This project had two objectives: establish baseline IgY levels in Steller's and spectacled eider yolk under controlled captive conditions and evaluate the effect of year, laying date, egg fertility, egg incubation duration, individual hen, hen age and mass, and laying order to determine which variables influenced IgY levels. Average IgY concentrations were 0.03–0.48 mg ml−1 in Steller's eider yolk and 0.10–0.51 mg ml−1 in spectacled eider yolk. The year and individual hen influenced IgY concentration in Steller's and spectacled eider yolk. The laying date was negatively correlated with egg IgY levels for most Steller's eider hens, but laying order was positively correlated with egg IgY concentration for spectacled eiders.