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No band color effects on male courtship rate or body mass in the zebra finch: four experiments and a meta-analysis.

Seguin A, Forstmeier W - PLoS ONE (2012)

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: Max Planck Institute for Ornithology, Seewiesen, Germany.

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.

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Related in: MedlinePlus

Mean ± SE of courtship rate (square-root transformed seconds of song) recorded after manipulating males with color bands during the juvenile period.All males were housed in groups of four males with four females during this period, and within each experimental group the four males were either all wearing the same color bands (uni-color; i.e. all green or all red) or there were two males of each color (mixed color). Symbol colors represent the color assigned during the experiment. (A) shows the data for the wild-type and (B) for the domesticated population. The asterisk denotes a significant treatment effect.
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pone-0037785-g001: Mean ± SE of courtship rate (square-root transformed seconds of song) recorded after manipulating males with color bands during the juvenile period.All males were housed in groups of four males with four females during this period, and within each experimental group the four males were either all wearing the same color bands (uni-color; i.e. all green or all red) or there were two males of each color (mixed color). Symbol colors represent the color assigned during the experiment. (A) shows the data for the wild-type and (B) for the domesticated population. The asterisk denotes a significant treatment effect.

Mentions: We also found four studies reporting color band effects on male body mass. Zann [16] presents body mass of red- and green-banded males in the wild at the start and at the end of the breeding season, and we entered these as two estimates despite their non-independence. Cuthill et al. [23] report different effects of color bands on body mass depending on the time of day (dusk versus dawn), so we also include these as two estimates. From the latter study we extracted the data from Figure 1a (using Engauge Digitizer), and averaged the values (means and SEs) for red and green-banded males across the 20 days of the study period. For both these studies our analyses are cross-sectional (like for all the above studies on courtship rate). For two studies on body mass we were able to use longitudinal data, namely Pariser et al. [25] and Schuett and Dall [7]; in the latter case we obtained the raw data from the Authors.


No band color effects on male courtship rate or body mass in the zebra finch: four experiments and a meta-analysis.

Seguin A, Forstmeier W - PLoS ONE (2012)

Mean ± SE of courtship rate (square-root transformed seconds of song) recorded after manipulating males with color bands during the juvenile period.All males were housed in groups of four males with four females during this period, and within each experimental group the four males were either all wearing the same color bands (uni-color; i.e. all green or all red) or there were two males of each color (mixed color). Symbol colors represent the color assigned during the experiment. (A) shows the data for the wild-type and (B) for the domesticated population. The asterisk denotes a significant treatment effect.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3369886&req=5

pone-0037785-g001: Mean ± SE of courtship rate (square-root transformed seconds of song) recorded after manipulating males with color bands during the juvenile period.All males were housed in groups of four males with four females during this period, and within each experimental group the four males were either all wearing the same color bands (uni-color; i.e. all green or all red) or there were two males of each color (mixed color). Symbol colors represent the color assigned during the experiment. (A) shows the data for the wild-type and (B) for the domesticated population. The asterisk denotes a significant treatment effect.
Mentions: We also found four studies reporting color band effects on male body mass. Zann [16] presents body mass of red- and green-banded males in the wild at the start and at the end of the breeding season, and we entered these as two estimates despite their non-independence. Cuthill et al. [23] report different effects of color bands on body mass depending on the time of day (dusk versus dawn), so we also include these as two estimates. From the latter study we extracted the data from Figure 1a (using Engauge Digitizer), and averaged the values (means and SEs) for red and green-banded males across the 20 days of the study period. For both these studies our analyses are cross-sectional (like for all the above studies on courtship rate). For two studies on body mass we were able to use longitudinal data, namely Pariser et al. [25] and Schuett and Dall [7]; in the latter case we obtained the raw data from the Authors.

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: Max Planck Institute for Ornithology, Seewiesen, Germany.

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.

Show MeSH
Related in: MedlinePlus