Factors associated with leucism in the common blackbird Turdus merula
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AuthorIzquierdo, Lucía; Thomson, Robert L.; Aguirre, José I.; Díez Fernández, Alazne; Faivre, Bruno; Figuerola, Jordi; Ibáñez Álamo, Juan Diego
Avian colorationCitizen scienceUrbanization
Izquierdo, L., Thomson, R. L., Aguirre, J. I., Díez‐Fernández, A., Faivre, B., Figuerola, J., & Ibáñez‐Álamo, J. D. (2018). Factors associated with leucism in the common blackbird Turdus merula. Journal of avian biology, 49(9), e01778.
SponsorshipJDI was funded by a postdoctoral contract (TAHUB- 104) from the program ‘Andalucía Talent Hub’ (co-funded by the European’s Union Seventh Framework Program Marie Skłodowska- Curie actions – COFUND – and the regional Government of Andalucía). ADF was funded by a Severo Ochoa grant (SVP-2014- 068571) from MICINN (Spain).
Leucism is the total or partial lack of melanins in the skin and associate structures (i.e. hair or feathers). Little is known about the factors influencing this chromatic aberration although some local studies suggest that there is an effect of habitat, age and sex. To test these hypotheses and expand our knowledge on leucism, we carried out a large-scale study using common blackbirds Turdus merula as our model species. Given the poor information available on this topic and the variability of methodological approaches, we used three different methods to assess the effect of these variables in the presence of leucism: transects, bird captures and citizen science information (pictures from internet). We found an effect of habitat indicating that there are more leucistic blackbirds in cities than in non-urban areas. In addition, we found a positive association between presence of white feathers and age providing the first large-scale support for the progressive graying hypothesis in birds. This chromatic aberration was also influenced by sex, with males showing higher probability of leucism than females, although only for the capture data, indicating that the method used to study this phenomenon can partly influence our conclusions, and therefore suggesting caution when planning future studies in this topic.