Population of the Parana Antwren Formicivora acutirostris reassessed as being 64% smaller: Revision of its conservation status and assessment of its Green Status, with management proposals

Assessing the conservation status of a species is important for designing effective conservation measures. Consequently, it is often vital to review it to update biodiversity management. Formicivora acutirostris is a bird from coastal marshes and related habitats of Brazils southern flood plains. It is considered endangered in Brazil but near threatened globally. In 2007, its area of occupancy (AOO) and population size were estimated based on assessment of aerial photographs from 1978 and 1980. Since the species is threatened and occupies a small area scattered across a coastal pressured region, we aimed to reassess its conservation status and assess its Green Status. We compiled new records, conducted new density estimates, and compared the previous mapping with orbital imagery to estimate the current AOO, habitat loss, population size, and review its conservation status based on the International Union for Conservation of Nature criteria. The species is distributed across 10 populations, including two new populations from the southern coast of Santa Catarina to the northern coast of Rio Grande do Sul. We estimated the AOO at 4,102 ha and the population as 6,284 mature territorial individuals. The previously mapped AOO has decreased by 1,535 ha due to ecological succession. The loss of habitat due to invasion by exotic grasses is the main anthropogenic impact. We recommend that the species be considered vulnerable. The Green Status indicates that the Conservation Legacy of actions taken thus far and the Conservation Dependence of ongoing actions are null, but it highlights the importance of future actions for species conservation. We propose the establishment of exotic-free zones as small geographic areas with a significant amount of minimally invaded environments, which we suggest as priority areas for the conservation of the species due to their cost-effective management potential. We also propose assisted colonization to enhance its long-term conservation.