Habitat selection across scales by the threatened Bearded Tachuri ( Polystictus pectoralis )

Despite the widespread loss of Neotropical grasslands and wetlands, some specialist bird species persist in agroecosystems that retain seminatural or natural grassland patches. The Bearded Tachuri (Polystictus pectoralis, Tyrannidae) is a migratory tall-grassland specialist primarily threatened by habitat loss due to agricultural expansion, yet the structure and composition of its breeding areas remain poorly characterized. We modeled Bearded Tachuri’s probability of occurrence and mapped critical breeding habitats by associating presence-absence data with environmental characteristics at local and landscape scales, recorded across a gradient of land uses (from agroecosystems to pristine grassland relicts) in central eastern Argentina. Our results indicate that the number of vegetation strata, along with the cover of shrubland and Sporobolus grasslands, are key environmental factors shaping Bearded Tachuri’s habitat selection. The species showed a clear preference for areas where these factors spatially converge and preferred pristine relicts over agroecosystems. In conclusion, the Bearded Tachuri is strongly associated with spatial heterogeneity in grassland and wetland communities, selectively using vegetation types and landscape types based on structure and composition, respectively. Given its specific habitat preferences and sensitivity to vegetation structure, the Bearded Tachuri could serve as an umbrella species, with the conservation of its habitat benefiting other co-occurring grassland specialists.