Limits...
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.

Show MeSH
Mean ± SE of body mass measured after manipulating males 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.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3369886&req=5

pone-0037785-g002: Mean ± SE of body mass measured after manipulating males 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.

Mentions: The total number of relevant published studies (N  = 7, see below) was too small to require a formal review protocol. They were identified by a Web of Knowledge (covering 1864–2011) search for “zebra finch* and (color* or colour*) and (band* or ring*)” which yielded 77 hits (on 29th Nov 2011). Twenty seven of those actually represented studies reporting effects of red and green bands in the zebra finch, and an additional four studies were identified via forward and backward search through citations, yielding a total of 31 relevant studies (see Table S1). Among those 31 studies we found four studies presenting data on male courtship rate. These are the previously mentioned experiment by Pariser et al. [25] (data extracted from their Fig. 2 using the software Engauge Digitizer V. 4.1, http://digitizer.sourceforge.net), two experiments (on separate sets of birds housed in different group sizes) reported by Gleeson [39], and two experiments (on the same set of birds but with colors swapped among males) reported by Ratcliffe and Boag [24] (data taken from their Table 1B). We further included the study by Burley et al. [14] who reported rates of extra-pair courtship behavior by red- and green-banded males. While Pariser et al. [25], Gleeson [39], and the present study focus on courtship rate of unpaired males in standardized tests, the study by Ratcliffe and Boag [24] reports courtship of a mix of paired and unpaired males in socially complex aviary conditions, and Burley et al. [14] report only extra-pair courtships in such aviary conditions. Although the latter two studies may not be fully comparable to the others, we include them for the sake of statistical conservatism (since they report higher courtship rates by red-banded males, and we prefer to have all positive evidence included). We did not include data about color band effects on the rate of undirected singing [24], [40] since courtship and undirected singing are two very distinct behaviors with different functions and different proximate control mechanisms [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 body mass measured after manipulating males 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.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0037785-g002: Mean ± SE of body mass measured after manipulating males 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.
Mentions: The total number of relevant published studies (N  = 7, see below) was too small to require a formal review protocol. They were identified by a Web of Knowledge (covering 1864–2011) search for “zebra finch* and (color* or colour*) and (band* or ring*)” which yielded 77 hits (on 29th Nov 2011). Twenty seven of those actually represented studies reporting effects of red and green bands in the zebra finch, and an additional four studies were identified via forward and backward search through citations, yielding a total of 31 relevant studies (see Table S1). Among those 31 studies we found four studies presenting data on male courtship rate. These are the previously mentioned experiment by Pariser et al. [25] (data extracted from their Fig. 2 using the software Engauge Digitizer V. 4.1, http://digitizer.sourceforge.net), two experiments (on separate sets of birds housed in different group sizes) reported by Gleeson [39], and two experiments (on the same set of birds but with colors swapped among males) reported by Ratcliffe and Boag [24] (data taken from their Table 1B). We further included the study by Burley et al. [14] who reported rates of extra-pair courtship behavior by red- and green-banded males. While Pariser et al. [25], Gleeson [39], and the present study focus on courtship rate of unpaired males in standardized tests, the study by Ratcliffe and Boag [24] reports courtship of a mix of paired and unpaired males in socially complex aviary conditions, and Burley et al. [14] report only extra-pair courtships in such aviary conditions. Although the latter two studies may not be fully comparable to the others, we include them for the sake of statistical conservatism (since they report higher courtship rates by red-banded males, and we prefer to have all positive evidence included). We did not include data about color band effects on the rate of undirected singing [24], [40] since courtship and undirected singing are two very distinct behaviors with different functions and different proximate control mechanisms [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