Population of the Paraná AntwrenFormicivora acutirostrisreassessed as being 64% smaller: Revision of its conservation status and assessment of its Green Status, with management proposals

Abstract

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 acutirostrisis a bird from coastal marshes and related habitats of Brazil’s 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.

Short-term extinction predicted by population viability analysis for a Neotropical salt marsh endemic bird

“…The species is distributed across the subtropical coastal marshes of southern Brazil between 25º16'-29º23'S and 48º27'-49º55'W (Bornschein et al 2023). The climate is humid subtropical, with hot summers (Cfa), according to the Köppen classi cation (Alvares et al 2014).…”

“…Annual rainfall and average temperature decrease from north to south, ranging from 2,550-1,300 mm and from 22-18°C, respectively (Alvares et al 2014). There are 10 isolated F. acutirostris populations, totaling an estimated 4,102 ha of area of occupancy and 6,284 mature individuals (Bornschein et al 2023; Table 2). The birds' subtropical salt marsh habitats are inundated daily by mixed semi-diurnal tides (Lee and Chang 2019).…”

“…These environments include transition zones toward arboreal forest formations upstream and mangroves downstream (Reinert et al 2007). The species also occur marginally in marshes close to these but without tidal in uence (Reinert et al 2007;Bornschein et al 2023). All the species' habitats are transitory and transition into forests as sediment accumulation increases elevation and reduces ooding (Reinert et al 2007;Bornschein et al 2023; see Veloso et al 1991).…”

“…Subpopulations meeting the rst criterion were then called "emigrant" due to the possible loss of individuals to subpopulations of the second ("immigrant") type (see Section 2.5.4). Finally, we assessed the areas of occupancy by habitat type for each subpopulation and multiplied the value by the corresponding density of individuals for that habitat type, according to Bornschein et al (2023), to estimate the population sizes of territorial F. acutirostris adult individuals in 2023, by subpopulation.…”

“…We treated species population size estimated by Bornschein et al (2023) as the current carrying capacity.…”