Behaviour 150 (2013) 1641–1663 brill.com/beh Mating strategies, parental investment and mutual ornamentation in Iberian Rock Sparrows (Petronia petronia) Vicente García-Navas a,∗ , Amanda García del Rincón b , Esperanza S. Ferrer a,b and Hicham Fathi b a Grupo de Investigación de la Biodiversidad Genética y Cultural, Instituto de Investigación en Recursos Cinegéticos CSIC-UCLM-JCCM, Ronda de Toledo, s/n 13071, Ciudad Real, Spain b Departamento de Ciencias Ambientales, Facultad de Ciencias Ambientales y Bioquímica, Universidad de Castilla-La Mancha, Avenida Carlos III, s/n 45071, Toledo, Spain * Corresponding author’s e-mail addresses: vicente.garcianavas@uclm.es, vicente.garcianavas@gmail.com Accepted 25 June 2013 Abstract Relatively few bird species show complex social mating systems whose preponderance in a pop- ulation is likely to affect the patterns of parental care observed there. In turn, parental investment is likely to be related to the expression of certain ornaments, which may reveal information on the bearer’s individual quality. Here we address both issues in a species characterised by several forms of parental care (both biparental and uniparental care) and in which both sexes possess a yellow breast patch, the rock sparrow (Petronia petronia). In our population, males contributed more to the care of the young in comparison with other populations. Social monogamy was the most frequent mating pattern and the percentage of cases of female (or male) brood desertion was lower with respect to that reported in previous studies, suggesting a flexible behaviour of this species to deal with different social environments. Birds did not pair assortatively with respect to the size of the yellow breast patch and we found no significant relationship between this trait and the frequency with which parents provisioned their chicks. However, we observed a positive relationship between male yellow patch size and nestling tarsus length, which suggests that more ornamented males are better parents. Males, but not females, differentially allocated parental investment in response to female ornamentation, although the benefits that males may gain from choosing more attractive females remain unidentified. Our results on paternal care investment along with previous studies on this species, reinforcing the view that the rock sparrow constitutes a good model to study sexual conflict over parental care under different social environments.  2013 Koninklijke Brill NV, Leiden DOI:10.1163/1568539X-00003112