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

Abstract

Salt marshes pose challenges for the birds that inhabit them, including high rates of nest ooding, tipping, and predation. The impacts of rising sea levels and invasive species further exacerbate these challenges. To assess the urgency of conservation and adequacy of new actions, researchers and wildlife managers may use population viability analyses (PVAs) to identify population trends and major threats. We conducted PVA for Formicivora acutirostris, which is a threatened neotropical bird species endemic to salt marshes. We studied the species' demography in different sectors of an estuary in southern Brazil from 2006-2023 and estimated the sex ratio, longevity, productivity, rst-year survival, and mortality rates. For a 133-year period, starting in 1990, we modeled four scenarios: 1) pessimistic and 2) optimistic scenarios, including the worst and best values for the parameters; 3) a baseline scenario, with intermediate values; and 4) scenarios under conservation management, with increased recruitment and/or habitat preservation. Projections indicated population decline for all assessment scenarios, with a 100% probability of extinction within 34 years in the pessimistic scenario and no extinction in the optimistic scenario. The conservation scenarios indicated population stability with 16% improvement in productivity, 10% improvement in rst-year survival, and stable carrying capacity. The disjunct distribution of the species, with remnants concentrated in a broad interface with arboreal habitats, may seal the population decline by increasing nest predation. The species should be considered conservation dependent, and we recommend assisted colonization, predator control, habitat recovery, and ex situ conservation. et al. 2006). Subtropical salt marsh birds also lose nests due to ooding by high tides (Bornschein et al. 2022), but climatic conditions and the proximity of this environment to forests potentially exacerbate nest predation, which is a primary cause of reproductive failure in tropical birds (Oniki 1979;Winkler 2016).Additionally, salt marshes and other estuarine environments are generally vulnerable to sea-level increases, rising temperatures, changes in precipitation patterns, and alterations in river ows (Marengo 2006). Climate change models have predicted that sea levels will rise by up to 2 m by 2100 (IPCC 2013; Sweet et al. 2022), which could lead to drastic habitat reductions for estuarine species (Erwin et al. 2006; IPCC 2007). Some species are already responding to climate change (e.g., Møller et al. 2004Møller et al. , 2010Lemoine et al. 2007;Houston et al. 2020), while others are facing extinction (Pounds et al. 1999;Imberti and Casañas 2010). In addition to the effects of climate change, the emergence of infectious diseases, invasion by exotic species, and habitat loss due to human activities constitute growing threats to biodiversity (Brodie 2016;Doherty et al. 2016). To reduce data uncertainty and support decisions regarding conservation actions in complex ecological systems, researchers ...