Data from: No mutual mate choice for quality in zebra finches: time to question a widely-held assumption

Studies of mate choice typically assume that individuals will prefer high quality mates and select them based on condition-dependent indicator traits. In species with bi-parental care, mutual mate choice is expected to result in assortative mating for quality. When assortment is not perfect, the lower quality pair members are expected to compensate by increased parental investment in order to secure their partner (positive differential allocation). This framework has been assumed to hold for monogamous model species like the zebra finch (Taeniopygia guttata), but progress has been hampered by the difficulty of defining individual quality. By combining multiple measures of causes and consequences of variation in quality into a single principal component, we here show that quality variation can be quantified successfully, and it indeed predicts individual pairing success. Yet, despite high statistical power, we found no evidence for either assortative mating or for positive differential allocation. We suggest that zebra finch ornaments and displays are not sufficiently reliable for the benefits of choosiness to exceed the costs of competition for the putative best partner. To assess the generality of this we would require unbiased quantification of signal honesty and preference strength rather than selective reporting of significant results.