Kinship and genetic mating system of the Grayish Baywing (Agelaioides badius), a cooperatively breeding Neotropical blackbird

Cynthia A. Ursino, María Cecilia De Mársico, Juan Carlos Reboreda, Christina Pauline Riehl

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


Kin selection theory predicts that extrapair mating should be rare in cooperatively breeding birds. However, most cooperative breeders are not genetically monogamous and the relationship between promiscuity and cooperative breeding remains unclear. This relationship is further complicated by a lack of data. The majority of cooperatively breeding birds live in the tropics, and their genetic mating systems are little known. Here we studied the genetic mating system of the Grayish Baywing (Agelaioides badius), a socially monogamous Neotropical blackbird in which most nesting pairs are assisted by helpers, previously assumed to be offspring of the breeding pair. Grayish Baywings are the primary host of the parasitic Screaming Cowbird (Molothrus rufoaxillaris), and previous studies have found a positive association between brood parasitism and helper recruitment in the last part of the nestling period. We used microsatellite markers to analyze the kinship of 192 individuals in 47 breeding groups, finding that 13% of 153 nestlings (in 38% of 47 nests) resulted from extrapair mating. We also documented 2 instances of conspecific brood parasitism and 1 instance of quasiparasitism (the nestling was sired by the social father, but was unrelated to the social mother). Of 8 helpers that were genotyped, 4 (all males) were offspring of the breeding pair and 4 (2 males, 2 females) were unrelated to both members of the breeding pair. None of the helpers produced offspring within the clutch. These results suggest that, although cooperative breeding is frequent, genetic relatedness between Grayish Baywing helpers and the offspring that they raise is highly variable. Future studies are needed to determine why unrelated helpers assist at Grayish Baywing nests, and to understand the role that brood parasitism may have played in the evolution of cooperative breeding in this species.

Original languageEnglish (US)
Pages (from-to)410-420
Number of pages11
Issue number2
StatePublished - Apr 1 2017

All Science Journal Classification (ASJC) codes

  • Ecology, Evolution, Behavior and Systematics
  • Animal Science and Zoology


  • Agelaioides badius
  • cooperative breeding
  • extrapair mating
  • mating system
  • microsatellite markers
  • parentage analysis


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