Subtropical grasslands are highly susceptible to habitat conversion and number among South America’s most threatened ecosystems. The grasslands of northeastern Argentina have been identified as a priority conservation area for threatened capuchino seedeaters because they constitute the main breeding area of these migratory birds. The Iberá Seedeater (Sporophila iberaensis) is a newly described species in the Iberá Wetlands in Argentina whose biology is still poorly understood. The endangered species inhabits grasslands but has only been reported to breed in the Iberá Wetlands ecoregion of northeastern Argentina. To explore the species’ association with grassland vegetation, we studied the breeding biology (clutch size, hatching success, and fledgling production) of the Iberá Seedeater and the main parameters that influence nest survival and nest-site selection. We conducted nest searches and banded adults and nestlings in Iberá National Park during the breeding seasons of 2016–2018. The breeding season of the Iberá Seedeater was highly synchronous and the cumulative probability of nest survival was 0.16. The daily nest survival rate decreased as the breeding season advanced, survival was lower for nests supported by Rhynchospora corymbosa than Paspalum durifolium, the two main nest substrates, and the main causes of nest failure were nest predation and strong winds. Additionally, the population exhibited male-biased site fidelity and a low female return rate. In contrast to other capuchinos, whose breeding biology is associated with upland grasslands, the Iberá Seedeater nested exclusively in flooded lowland grasslands on marsh plants. Thus, effective lowland grassland management is key to maintain the vegetation structure required for reproduction in the Iberá Seedeater.

中文翻译：

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濒临灭绝的 Iberá Seedeater 在其唯一已知的繁殖地阿根廷伊比利亚湿地的繁殖成功率低

南美洲最受威胁的生态系统中，亚热带草原极易受到栖息地转换和数量的影响。阿根廷东北部的草原已被确定为受威胁的卷尾猴的优先保护区，因为它们构成了这些候鸟的主要繁殖区。Iberá Seedeater (Sporophila iberaensis) 是阿根廷伊比利亚湿地新发现的物种，其生物学仍然知之甚少。这种濒临灭绝的物种栖息在草原上，但仅据报道在阿根廷东北部的伊比利亚湿地生态区繁殖。为了探索该物种与草原植被的关联，我们研究了繁殖生物学（离合器大小、孵化成功率、和羽翼未丰的生产）的伊比利亚播种机和影响巢生存和巢址选择的主要参数。在 2016 年至 2018 年的繁殖季节，我们在伊比利亚国家公园进行了巢穴搜索和带状成虫和雏鸟。Iberá Seedeater 的繁殖季节高度同步，巢穴存活的累积概率为 0.16。随着繁殖季节的推进，日巢成活率下降，以伞房花为支撑的巢穴的成活率低于硬叶雀稗这两种主要的巢穴基质，巢穴失败的主要原因是巢穴捕食和强风。此外，该人群表现出偏向男性的网站保真度和较低的女性回归率。与其他繁殖生物学与高地草原有关的卷尾猴相比，Iberá Seedeater 只筑巢在沼泽植物上被淹的低地草原上。因此，有效的低地草原管理是维持 Iberá Seedeater 繁殖所需的植被结构的关键。