Many fields of science currently experience a heated debate about the extent of publication bias against null-findings. Here, we show a case where putatively well-established text-book knowledge cannot be confirmed. Across four decades, zebra finch (Taeniopygia guttata) studies have reported effects of bands of certain colors on male or female attractiveness and further on behavior, physiology, life-history and fitness. Only 8 out of 39 publications presented exclusively null-findings. Here, we analyze the results of eight experiments in which we quantified the fitness of 730 color-banded individuals from four captive populations (two domesticated and two recently wild-derived). This sample size exceeds the combined sample size of all 23 publications that clearly support the “color-band effect” hypothesis. In our populations, band color explained no variance in fitness and there were no context- or population-specific band color effects. Analysis of unpublished data from three other laboratories strengthens our null finding. Finally, a meta-analysis of previously published results is indicative of selective reporting and suggests that the effect size approaches zero when sample size is large. We argue that our field would benefit from more effective means to counter confirmation bias and publication bias.