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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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Mean ± SE of male courtship rate (transformed) before and after manipulating males by adding color bands during adulthood.Filled symbols indicate the color of the band that males were allocated and empty symbols refer to the measurement before color bands were added. (A) Males from the wild-type population (W ad), maintained in one large group containing 10 red-banded males (red symbols), 10 green-banded males (green) and 11 un-banded control males (grey); (B) males from the domesticated population (D ad), maintained in groups of two (one red-banded, one green-banded); (C) males from the domesticated population (D ad), changing from the group size of two (“before” shows the same data as the “after” in (B) but with different grouping of individuals) to groups of 10 or 11 males (with about equal numbers of red-banded and green-banded males).
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pone-0037785-g003: Mean ± SE of male courtship rate (transformed) before and after manipulating males by adding color bands during adulthood.Filled symbols indicate the color of the band that males were allocated and empty symbols refer to the measurement before color bands were added. (A) Males from the wild-type population (W ad), maintained in one large group containing 10 red-banded males (red symbols), 10 green-banded males (green) and 11 un-banded control males (grey); (B) males from the domesticated population (D ad), maintained in groups of two (one red-banded, one green-banded); (C) males from the domesticated population (D ad), changing from the group size of two (“before” shows the same data as the “after” in (B) but with different grouping of individuals) to groups of 10 or 11 males (with about equal numbers of red-banded and green-banded males).

Mentions: Red-banded males of the Wad group did not differ significantly in their change of courtship rate (after minus before treatment) from green-banded males or from un-banded males (red: mean±SD  =  +0.82±0.81, n = 10; green: mean±SD  =  +0.88±1.70, n = 10; un-banded: mean±SD  =  +1.68±1.54, n = 11; LMM: F2,11 = 1.22, p = 0.33, Fig. 3a; effect size red vs. green d = −0.05). However, it may be noteworthy that 25 out of 31 males increased their courtship rate (paired t-test: t30 = 4.48, p = 0.0001). Treatment groups did also not differ in their body mass changes during this experiment (red: mean±SD  =  +0.01±0.60, n = 10; green: mean±SD  =  +0.21±0.37, n = 10; un-banded: mean±SD  =  +0.18±0.57, n = 11; LMM: F2,11 = 0.35, p = 0.71, Fig. 4a; effect size red vs. green d = −0.41).


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 male courtship rate (transformed) before and after manipulating males by adding color bands during adulthood.Filled symbols indicate the color of the band that males were allocated and empty symbols refer to the measurement before color bands were added. (A) Males from the wild-type population (W ad), maintained in one large group containing 10 red-banded males (red symbols), 10 green-banded males (green) and 11 un-banded control males (grey); (B) males from the domesticated population (D ad), maintained in groups of two (one red-banded, one green-banded); (C) males from the domesticated population (D ad), changing from the group size of two (“before” shows the same data as the “after” in (B) but with different grouping of individuals) to groups of 10 or 11 males (with about equal numbers of red-banded and green-banded males).
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3369886&req=5

pone-0037785-g003: Mean ± SE of male courtship rate (transformed) before and after manipulating males by adding color bands during adulthood.Filled symbols indicate the color of the band that males were allocated and empty symbols refer to the measurement before color bands were added. (A) Males from the wild-type population (W ad), maintained in one large group containing 10 red-banded males (red symbols), 10 green-banded males (green) and 11 un-banded control males (grey); (B) males from the domesticated population (D ad), maintained in groups of two (one red-banded, one green-banded); (C) males from the domesticated population (D ad), changing from the group size of two (“before” shows the same data as the “after” in (B) but with different grouping of individuals) to groups of 10 or 11 males (with about equal numbers of red-banded and green-banded males).
Mentions: Red-banded males of the Wad group did not differ significantly in their change of courtship rate (after minus before treatment) from green-banded males or from un-banded males (red: mean±SD  =  +0.82±0.81, n = 10; green: mean±SD  =  +0.88±1.70, n = 10; un-banded: mean±SD  =  +1.68±1.54, n = 11; LMM: F2,11 = 1.22, p = 0.33, Fig. 3a; effect size red vs. green d = −0.05). However, it may be noteworthy that 25 out of 31 males increased their courtship rate (paired t-test: t30 = 4.48, p = 0.0001). Treatment groups did also not differ in their body mass changes during this experiment (red: mean±SD  =  +0.01±0.60, n = 10; green: mean±SD  =  +0.21±0.37, n = 10; un-banded: mean±SD  =  +0.18±0.57, n = 11; LMM: F2,11 = 0.35, p = 0.71, Fig. 4a; effect size red vs. green d = −0.41).

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