No Band Color Effects on Male Courtship Rate or Body Mass in the Zebra Finch: Four Experiments and a Meta-Analysis

Abstract

Replication of experiments is essential for distinguishing real effects from type 1 errors and idiosyncrasies. One of the most replicated experiments in behavioral ecology is the presumed manipulation of male attractiveness in zebra finches by adding red or green color bands. Red-banded males were found to have higher fitness than green-banded males, and most empirical evidence suggests that this effect is mediated by female mating preferences rather than by male-male competition. A recent study, however, reported that color bands affected male courtship rate and body mass independently of female behavior. If this effect was real, some earlier findings of female preferences and maternal effects on offspring traits could potentially be reinterpreted as being mediated indirectly via effects on male behavior. This new perspective seems appealing also in light of a growing interest in bi-directional feedback mechanisms between endocrinology and ornamentation. However, here we report four independent failures to replicate this effect of color bands on courtship rate and body mass. Combining this new experimental data with all the published evidence in a meta-analysis shows that color bands seem to affect neither male courtship rate (average effect size d = 0.02) nor male body mass (d = −0.07). The present case is a reminder that replication of experiments lies at the heart of distinguishing between real effects and false positive findings.

Detecting and avoiding likely false‐positive findings – a practical guide

“…For instance, when reporting a result, we may calculate a 95% confidence interval around our estimate, and then highlight that our study shows an effect that is significantly smaller than this or that quantity. We can calculate a weighted average of the two results, and as we accumulate more independent replications, we gain confidence in our average, and if this average approximates zero, we become more confident that the hypothesis in question is wrong, or at least of extremely narrow applicability (Seguin & Forstmeier, 2012;Nakagawa & Parker, 2015).…”

Personality in captivity: More exploratory males reproduce better in an aviary population

“…Individuals wore one of 15 randomly-allocated band colours with the PIT-tag attached from the aviary foraging test onwards, (the PIT-tag and its glue obscured most of the band so little colour was showing), and also one of 45 different colour bands in the aviary experiment for identification. Although the issue of colour bands influencing attractiveness has been overstated in previous research (Seguin and Forstmeier, 2012), we reduced any potential effect in this experiment by having no birds wear a red band and only one wear a green band (the two colours for which some effect has been shown). In only one case (where a male was not recorded to visit the nest) were we unable to identify a social mother or father from either PIT-tag or observational data.…”

Colour Cues That Are Not Directly Attached to the Body of Males Do Not Influence the Mate Choice of Zebra Finches

“…These authors added colour bands (red/green) to zebra finches and failed to replicate earlier results with regard to courtship rates and body mass; furthermore, they showed in a meta-analysis that overall support from the literature associated with colour bands attached to males in this context is limited [25]. Here, I found similar patterns, but in a new context, where artificial ornaments were not attached to the male body.…”

“…Mate choice paradigms appear to be complex with regard to the cues subjects can rely on, and the repeatability of colour ring effects can be problematic, as demonstrated by another study [25]. These authors added colour bands (red/green) to zebra finches and failed to replicate earlier results with regard to courtship rates and body mass; furthermore, they showed in a meta-analysis that overall support from the literature associated with colour bands attached to males in this context is limited [25].…”

“…However, other studies again failed to confirm these effects [21]. In addition, in some studies, red rings have been observed to increase the male courtship rate [24], whereas other studies failed to support this finding [25]. Common preference tests, e.g., choice chambers, also support the positive effects of red rings on mate attractiveness (e.g., [14,26,27]), but again another study failed to support these observations [28].…”