Related Experiment Video
Updated: Jun 1, 2026
08:14
Who is Who? Non-invasive Methods to Individually Sex and Mark Altricial Chicks
Published on: May 24, 2014
Digit ratios have poor indicator value in a wild bird population
Behavioral Ecology and Sociobiology
|June 1, 2011
Summary
Digit ratios do not reliably indicate early androgen exposure in pied flycatchers. These measurements showed no link to reproductive traits or behavior, questioning their evolutionary significance.
Area of Science:
- Evolutionary biology
- Animal behavior
- Endocrinology
Background:
- Early androgen exposure influences phenotype, behavior, and fitness.
- Digit ratios are proposed indicators of prenatal steroid levels, but evidence is limited.
- Experimental studies in wild populations are scarce.
Purpose of the Study:
- To investigate the association between yolk androgens and digit ratios (2D:4D, 2D:3D, 3D:4D) in pied flycatchers.
- To assess the indicator value of digit ratios for reproductive traits, secondary sexual traits, and exploratory behavior in an evolutionary context.
Main Methods:
- Correlative analysis of maternal yolk androgens and digit ratios.
- Experimental elevation of yolk androgens in pied flycatchers (Ficedula hypoleuca).
- Measurement of reproductive traits, secondary sexual traits, and exploratory behavior.
Main Results:
- No significant association found between digit ratios and yolk androgen levels (correlative or experimental).
- Digit ratios were not correlated with reproductive traits, secondary sexual traits, or exploratory behavior.
- A sex difference in 2D:3D and 3D:4D emerged in adults, not juveniles, suggesting later development.
Conclusions:
- Digit ratios are not reliable markers of yolk androgen exposure in pied flycatchers.
- Digit ratios have limited relevance as correlates of adaptive traits in this species.
- Observed adult sex differences in digit ratios may develop during sexual maturation.
Related Concept Videos
01:21Testing a Claim about Mean: Unknown Population SD
A complete procedure of testing a hypothesis about a population mean when the population standard deviation is unknown is explained here.
Estimating a population mean requires the samples to be approximately normally distributed. The data should be collected from the randomly selected samples having no sampling bias. There is no specific requirement for sample size. But if the sample size is less than 30, and we don't know the population standard deviation, a different approach is used; instead...
Estimating a population mean requires the samples to be approximately normally distributed. The data should be collected from the randomly selected samples having no sampling bias. There is no specific requirement for sample size. But if the sample size is less than 30, and we don't know the population standard deviation, a different approach is used; instead...
02:07Conservation of Declining Populations
Conservation of declining population focuses on ways of detecting, diagnosing, and halting a population decline. The approach uses methods to prevent populations from going extinct.
01:17Wald-Wolfowitz Runs Test II
The Wald-Wolfowitz runs test, commonly referred to as the runs test, is a nonparametric test used to assess the randomness of ordered data. The test evaluates the number of runs, which are consecutive sequences of similar elements within the data. If the number of runs is significantly higher or lower than expected, the data is considered non-random, indicating a detectable pattern or structure.
For binary data, runs are identified using symbols such as + and −, or equivalently, 1s and 0s. In...
For binary data, runs are identified using symbols such as + and −, or equivalently, 1s and 0s. In...
02:45The Ratio of X Chromosome to Autosomes
In most organisms, sex is determined by the ratio of X and Y chromosomes. However, in some organisms, such as Drosophila and C.elegans, sex is determined by the ratio of the number of X chromosomes to the number of sets of autosomes. The Y chromosome in Drosophila is active but does not determine sex. It contains genes responsible for the production of sperms in adult flies.
Normal male Drosophila has a ratio of one X chromosome to two sets of autosomes. In contrast, normal female Drosophila...
Normal male Drosophila has a ratio of one X chromosome to two sets of autosomes. In contrast, normal female Drosophila...
01:17Sign Test for Matched Pairs
The sign test for matched pairs offers a robust method for comparing two paired samples, often for the effects of an intervention in one of them. This method is very useful in situations where the underlying distribution of the data is unknown. The test compares two related samples—often pre- and post-treatment measurements on the same subjects—to determine if there are significant differences in their median values.
To conduct the sign test, we first calculate the differences in value between...
To conduct the sign test, we first calculate the differences in value between...
01:12Sign Test for Nominal Data
The sign test is a nonparametric method used to evaluate hypotheses about the median of a single sample or to compare the medians of two related samples. The sign test is particularly useful when dealing with nominal data, which includes distinct categories without an inherent order, such as names, labels, and preferences. Nominal data restricts statistical analysis to evaluating population proportions rather than mean or median values that require continuous data.
For example, consider a...
For example, consider a...