Parque das Aves, Foz do Iguaçu, Paraná, Brazil.
Fundação Neotrópica do Brasil, Bonito, Mato Grosso do Sul, Brazil.
PLoS One. 2022 Jun 1;17(6):e0267355. doi: 10.1371/journal.pone.0267355. eCollection 2022.
The Blue-fronted Amazon (Amazona aestiva) is a Neotropical parrot with a large distribution in South America, including areas in Brazil, Bolivia, Argentina and Paraguay. A substantial part of the population of this parrot is concentrated in the Pantanal, a large wetland located in the center of South America. There, the clearing of forest and savannas has occurred through the years to accommodate beef-cattle pasture, and crops. Our objective was to understand the direct and indirect effects of time, availability of forest and savannas, and rainfall over the number of nestlings and fledged young of Blue-fronted Amazons inhabiting the southern Pantanal. We surveyed their nests from 1997 to 2018 and counted the number of nestlings produced and the number of fledglings capable to leave the nest in each year. Additionally, we used available data on the area covered by arboreal vegetation, and rainfall data collected at a Meteorological Station located in a central area of the study, as predictors of the numbers of nestlings and fledglings produced every year. Then, we applied structural equation modeling to examine both the direct and indirect effects of time, arboreal habitat availability, and annual cumulative rainfall on the number of nestlings and fledgling per nest. Finally, we estimated the long-term trend of the number of fledglings per nest as a surrogate to the populational trend of Blue-fronted Amazon. We found that none of the variables in our model explained the number of nestlings in nests, but the number of nestlings and the arboreal habitat availability directly and positively affected the number of fledglings. Time indirectly and negatively affected the number of fledglings per nest, whereas rainfall affected it indirectly positively. Additionally, we detected a concerning decrease of about 30% of the fledglings during the 22-years study, which could lead to a change in the species conservational status.
蓝帽亚马逊鹦鹉（Amazona aestiva）是一种分布于南美洲的热带鹦鹉，包括巴西、玻利维亚、阿根廷和巴拉圭等地区。该鹦鹉的大量种群集中在潘塔纳尔湿地，这是一个位于南美洲中心的大型湿地。多年来，为了容纳肉牛牧场和农作物，该地区的森林和草原不断被开垦。我们的目的是了解时间、森林和草原的可利用性以及降雨量对栖息在南潘塔纳尔的蓝帽亚马逊鹦鹉雏鸟和离巢幼鸟数量的直接和间接影响。我们在 1997 年至 2018 年期间对它们的巢穴进行了调查，并统计了每年产生的雏鸟和离巢幼鸟的数量。此外，我们还利用了有关树木植被覆盖面积的可用数据以及位于研究中心的气象站收集的降雨量数据，作为每年产生的雏鸟和离巢幼鸟数量的预测因子。然后，我们应用结构方程模型来检查时间、树木生境的可利用性和年累积降雨量对每个巢穴的雏鸟和离巢幼鸟数量的直接和间接影响。最后，我们估算了每个巢穴离巢幼鸟数量的长期趋势，作为蓝帽亚马逊鹦鹉种群趋势的替代指标。我们发现，我们的模型中的变量都无法解释巢穴中的雏鸟数量，但雏鸟数量和树木生境的可利用性直接且积极地影响离巢幼鸟的数量。时间间接地对每个巢穴的离巢幼鸟数量产生负面影响，而降雨量则间接地对其产生积极影响。此外，我们发现，在 22 年的研究期间，离巢幼鸟数量下降了约 30%，这可能导致该物种保护状况的改变。
