Birds: the beauty of the plumage of males does not guarantee them reproductive success

The study, coordinated by the Doñana Biological Station (EBD-CSIC) and the Pyrenean Institute of Ecology (IPE-CSIC) of Spain and published in the Journal of Evolutionary Biology, suggested that male birds with physical attractiveness would be more likely to reproduce, than the most beautiful ones, since a better appearance could generate greater disputes with other males and, therefore, less time and energy to spend on the breeding of offspring.

The research indicated that a lower coloration of the plumage of birds could have a reproductive advantage, depending on the social context. CSIC researchers recalled that one of the main weapons of animals to ensure the transmission of their genes is the development of sexual characteristics, as ornaments, that highlight their quality, but that the development and maintenance of high-quality sex ornaments is no easy task for anyone.

In many animals, such as birds, the colorful visual cues indicating their level of attractiveness are costly to produce and maintain, for example male pied flycatchers, a small migratory bird that signals its sexual appeal, as well as its social status, by coloring the back.

This coloration can range from pale brown to irresistible black zaino of dominant males, the specialists of the Spanish center explained in a statement.

However, showing great appeal, with the effort it demands, may not always be beneficial in terms of descent, and this was explained by the study of the Spanish experts.

In a densely populated forest crowded with competitors, having irresistibly dark plumage that also emphasizes the dominant character, should be synonymous with success. However, the scientific study by the CSIC did not support this idea.

This paper analyzes annual data on breeding density and plumage color for about 2,000 males examined since 1984 and contrary to expectations, individuals with intermediate colorations proved to be the most beneficiaries in reproductive terms.

This apparent contradiction could be due to the high price to be paid for individuals who show a sign of high sexual and social status.

“The most attractive males enjoy better breeding grounds or better females, but they are at the same time the center of attention, including those of their competitors. Defending their possessions can lead to physical exhaustion that reduces the care of chickens and compromises their survival,” explains Nacho Morales-Mata, the first author of the work.

Higher defense spending could ultimately favor males with intermediate coloration who, despite not having the best physique, could spend less time on disputes and more time and energy to get more chickens forward.

The study used “an individual data set from a population of pied flycatchers (Ficedula hypoleuca)” that were “monitored for 24 years to analyze the effect of reproductive density on phenotypic selection in dorsal plumage coloration, a hereditary and sexually selected adornment in males of this type. species”.

“Most studies of phenotypic selection in nature have focused on morphological and life history traits and have considered abiotic (climatic) variation as the main driver of selection. Consequently, our knowledge of the effects of biotic environmental variation on the phenotypic selection of sexual traits is scarce,” they said when basing the characteristics of the work.

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