Breeding biology and parental care of the Unicolored Blackbird ( Agelasticus cyanopus )

The success of avian breeding is significantly influenced by habitat loss and fragmentation. As wetlands and their biodiversity are degraded, it is essential to understand avian life-history traits to develop effective conservation strategies. The Unicolored Blackbird (Agelasticus cyanopus) is a Neotropical icterid that nests in wetlands. Despite being common in these habitats, information on its breeding biology and parental care is limited. In this study, we examined 33 nests over four breeding seasons in a central Argentine wetland. The mean clutch size was 3.29 ± 0.64 eggs, with a breeding success of 54%. We identified this bird as an effective host of the Shiny Cowbird (Molothrus bonariensis). Nest failures were primarily due to abandonment (50%) and predation (33%). Females performed nest building, incubation, and brooding nestlings, while males were dedicated to nest vigilance, defense, and brooding nestlings. Our findings contribute to understanding the breeding biology of the Unicolored Blackbird and highlight the importance of conserving wetland habitats for the long-term breeding success of this as well as other native species.