BEHAVIORAL ECOLOGY - ORIGINAL RESEARCH Maternal effects in the highly communal sociable weaver may exacerbate brood reduction and prepare offspring for a competitive social environment Rene ´ E. van Dijk • Corine M. Eising • Richard M. Merrill • Filiz Karadas • Ben Hatchwell • Claire N. Spottiswoode Received: 11 August 2011 / Accepted: 14 August 2012 Ó Springer-Verlag 2012 Abstract Maternal effects can influence offspring phe- notype with short- and long-term consequences. Yet, how the social environment may influence egg composition is not well understood. Here, we investigate how laying order and social environment predict maternal effects in the sociable weaver, Philetairus socius, a species that lives in massive communal nests which may be occupied by only a few to 100? individuals in a single nest. This range of social environments is associated with variation in a number of phenotypic and life-history traits. We investi- gate whether maternal effects are adjusted accordingly. We found no evidence for the prediction that females might benefit from modifying brood hierarchies through an increased deposition of androgens with laying order. Instead, females appear to exacerbate brood reduction by decreasing the costly production of yolk mass and antiox- idants with laying order. Additionally, we found that this effect did not depend on colony size. Finally, in accordance with an expected increased intensity of environmental stress with increasing colony size, we found that yolk androgen concentration increased with colony size. This result suggests that females may enhance the competitive ability of offspring raised in larger colonies, possibly pre- paring the offspring for a competitive social environment. Keywords Breeding density  Competition  Egg composition  Hatching asynchrony  Maternal investment Introduction The social environment in which animals live has impor- tant implications for their life-histories (Stearns 2000; Hau et al. 2010; Sze ´kely et al. 2010). Breeding density, for instance, is likely to influence the level of competition for resources (Kokko et al. 2004; Alonzo and Sheldon 2010), and parents may be able to improve their fitness by adjusting their offspring’s phenotype to the environment in which they live. One mechanism for parents to achieve this is through maternal effects (Mousseau and Fox 1998), which may be manifested in egg size, egg composition, laying date and parental care (Price 1998). Deposition of hormones (such as androgens) and carotenoids of maternal origin in avian egg yolk has been shown to depend on the position of the egg in the laying sequence (Schwabl 1993; Kozlowski and Ricklefs 2010), Communicated by Indrikis Krams. R. E. van Dijk (&)  B. Hatchwell Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Sheffield S10 2TN, UK e-mail: R.van.Dijk@sheffield.ac.uk C. M. Eising  C. N. Spottiswoode DST/NRF Centre of Excellence at the Percy FitzPatrick Institute of African Ornithology, University of Cape Town, Rondebosch 7701, South Africa C. M. Eising Behavioural Biology Research Group, University of Groningen, Nijenborg 7, 9747 AG Groningen, The Netherlands C. M. Eising Centre for Ecological and Evolutionary Studies, University of Groningen, 9700 CC Groningen, The Netherlands R. M. Merrill  C. N. Spottiswoode Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK F. Karadas Department of Animal Science, Faculty of Agriculture, University of Yuzuncu Yil, 65080 Van, Turkey 123 Oecologia DOI 10.1007/s00442-012-2439-0