Female animals transfer a variety of immune compounds (eg, antibodies, antimicrobials) to their embryos that impose maternal effects on offspring growth, protection, and immune trajectories (Bernardo 1996, Grindstaff, Brodie & Ketterson 2003). Henceforth, we will refer to these transgenerational effects as immune-based maternal effects. Species that undergo at least some development within the womb have a prolonged window for transmission of maternal compounds, which may be further extended through lactation (Grindstaff, Brodie & Ketterson 2003). Oviparous females, on the other hand, must deposit their entire contribution into one package, the egg. Studies of both domestic and wild birds have documented significant immunebased maternal effects on hatchling health through passive immunity (eg, Heller et al. 1990, Mondal & Naqi 2001, Sahin et al. 2001, Rahman et al. 2002, Ahmed & Akhter 2003) and growth promotion (eg, Heeb et al. 1998, Grindstaff 2008, Lozano & Ydenberg 2002), as well as long-term effects on life-time immune function (eg, Gasparini et al. 2006, Reid et al. 2006). With the prospect of such transgenerational benefits, it is likely that maternal egg provisioning is subject to significant positive selection (Grindstaff et al. 2003). However, many immune compounds must be synthesized by females prior to egg laying and, therefore, require the maintenance or