Extreme bill dimorphism leads to different but overlapping isotopic niches and similar trophic positions in sexes of the charismatic extinct huia

Barbara M. Tomotani (Corresponding author), Rodrigo B. Salvador, Amandine J.M. Sabadel, Colin M. Miskelly, Julie C.S. Brown, Josette Delgado, Patrick Boussès, Yves Cherel, Susan M. Waugh, Sarah J. Bury

Research output: Contribution to journal/periodicalArticleScientificpeer-review

Abstract

The New Zealand huia (Heteralocha acutirostris) had the most extreme bill sexual dimorphism among modern birds. Given the quick extinction of the species, the cause of the dimorphism could only be hypothesised to reflect different trophic niches and reduce male/female competition. We tested that hypothesis by combining museum specimens, geometric morphometrics, and isotopic analyses. We used geometric morphometrics to describe bill shape; measured bulk (δ15Nbulk) and (δ13Cbulk) values from feather as proxies of the birds’ foraging habitat and diet; and compared compound-specific stable isotopes analyses (CSIA) of nitrogen in amino acids (δ15NAA) in male–female pairs to estimate their trophic position. Sexes had significantly different, but overlapping feather δ15Nbulk and δ13Cbulk values, but δ15NAA indicated identical trophic positions and δ15Nbulk was not related to bill shape. Trophic position was less variable among females, consistent with a specialised foraging behaviour and, thus, supporting a partial male/female foraging segregation.

Original languageEnglish
JournalOecologia
VolumeIn press
DOIs
Publication statusE-pub ahead of print - 2021

Keywords

  • Compound-specific stable isotopes
  • Feeding ecology
  • Heteralocha acutirostris
  • Natural history collections
  • New Zealand
  • Passeriformes
  • Plan_S-Compliant-OA
  • International

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