Age and sex determination of Mallards Anas platyrhynchos in autumn

Authors

  • Stina Andersson Ottenby bird observatory
  • Daniel Bengtsson Centre for Ecology and Evolution in Microbial Model Systems, Linnaeus University
  • Magnus Hellström Ottenby bird observatory
  • Jonas Waldenström Centre for Ecology and Evolution in Microbial Model Systems, Linnaeus University

DOI:

https://doi.org/10.34080/os.v26.22530

Keywords:

ducks, waterfowl, bird ringing, bird banding, sexual dimorphism, Anatidae, moult

Abstract

Male and female mallards Anas platyrhynchos are easily told apart, whereas ageing is problematic, due to individual timing of moult and lack of easily defined age criteria. From examination and photographic documentation of mallards caught at Ottenby Bird Observatory (56°12′N, 16°24′E), we describe nine characters of plumage and bare parts to be used for ageing in autumn. The reliability of these characters was tested by letting experienced bird ringers determine putative age of birds from photos. Age determination from any single character proved to be uncertain, as correctly assigned mallard photos of each character was in the range of 51–85% for males and 48–89% for females. For both sexes, the lowest figure represented post-humerals and the highest represented tertials. Rectrices, tertial coverts, and greater coverts had high scores (71–85%). Using all characters, 91% of the males and 95% of the females were correctly aged. As young mallards, with the progress of pre-breeding moult (completed from October onwards), acquire tail and tertials identical to adults, untypical individuals are better not assigned to an age category.

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Published

2016-04-01

How to Cite

Andersson, S., Bengtsson, D., Hellström, M., & Waldenström, J. (2016). Age and sex determination of Mallards Anas platyrhynchos in autumn. Ornis Svecica, 26(2), 61–81. https://doi.org/10.34080/os.v26.22530

Issue

Section

Research Papers

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