DOI: 10.5061/dryad.rfj6q57jq
title: Data from: Diversity and dominance in bird assemblages across habitats in the Ñeembucú Wetlands Complex

description: Understanding how diversity responds to habitat heterogeneity in a
 landscape is a central issue for implementing effective conservation
 plans. In this study, we analyzed how the composition and abundance of
 neotropical bird assemblages vary among habitats in the Ñeembucú Wetlands
 Complex, the largest wetland system in Paraguay. Bird surveys were
 conducted during one year within dominant habitats in the landscape:
 riparian forests, natural grasslands, savannas, and anthropized sites. The
 Ñeembucú Wetlands Complex showed a high bird richness (209 species) that
 contrasted with a pattern of dominance by a small set of 16 species that
 comprised half of the abundance. This set of oligarchic species consists
 of generalist species that exploited a wide variety of habitats and were
 well adapted to human disturbance, contributing to an important overlap in
 the composition of assemblages.  However, despite this overall
 similarity, there is still significant differentiation in bird
 assemblages, especially between habitats with the most contrasting
 vegetation physiognomy. Riparian forests and savannas showed higher
 diversity values than the more structurally homogeneous grasslands. Also,
 all natural habitats showed, in general, higher diversity values than
 anthropized sites. Oligarchic species had higher importance in anthropized
 environments, which also had the most uneven distribution of abundance
 between species, indicating the dominance by a smaller number of species
 and the loss of ecological diversity as farmland and urban development
 increase.
description: <strong>Study area</strong> The
 study areas are located in the Humid Chaco ecoregion, in the Ñeembucú
 Department (southern Paraguay), and belong to the Ñeembucú Wetlands
 Complex. The regional climate is tropical humid with a marked seasonality:
 the mean annual precipitation averages 1400-1500 mm but with a dry season
 in winter. The average temperatures are around 16-17°C in winter
 (May-August) and 25-26°C in the warmer season (December-March). The
 altitude of the study area ranges between 50 and 124 m above sea level
 (a.s.l.). Four dominant habitat types were considered
 in the landscape: riparian forests, natural grasslands, savannas, and
 anthropized habitats. Riparian forests are directly or indirectly
 associated with water, as they are subject to periodic flooding during the
 summer; they can be found along the edges of rivers, streams, and lakes or
 forming forest islands surrounded by wetlands and floodplains. Primary
 forest patches have a main canopy that is up to 25 m high, dominated
 by <em>Enterolobium contortisiliquun</em>, <em>Syagrus
 romanzoffiana</em>, <em>Aspidosperma
 quebracho-blanco</em>, <em>Libidibia
 paraguariensis</em>, <em>Microlobius foetidus,</em> and
 <em>Guazuma ulmifolia</em>.  Savannas are also subject to
 periodic flooding and are found on soils with high clay and salt content.
 The dominant species is the palm <em>Copernicia alba</em>,
 with a sparse or absent shrub layer, and an herbaceous cover dominated by
 <em>Hyptis</em> <em>lappacea</em>,
 <em>Pluchea sagittalis</em>, and <em>Chromolaena
 christiaeana.</em> In the paleobasins of the Paraná River, where
 soils are sandy, the landscape is dominated by grasslands of
 <em>Andropogon</em> spp., <em>Coleataenia
 prionitis</em>, <em>Elionurus muticus</em>,
 <em>Sorghastrum pellitum</em>, and
 <em>Schizachyrium</em> spp., and sometimes with the presence
 of scattered woody species such as <em>Cecropia
 pachystachya</em> and <em>E. contortisiliquum</em>. The
 selected anthropized count points included modified sites with a clear
 human influence that were mainly located on ranches and the periphery of
 small townships and villages. They generally comprised individual houses
 with yards, barns, orchards, small pastures, and unpaved roads.
 <strong>Field sampling and data
 collection</strong> In the terrestrial habitats
 identified in the study area, bird surveys were carried out during 158
 point counts between October 2020 and July 2021. Forty-three points were
 selected in riparian forests, 30 in natural grasslands, 50 in
 <em>Copernicia</em> savannas, and 35 in anthropized sites. 
 The number of points per habitat was based on their importance within the
 landscape, but not directly proportional due to accessibility constraints
 and security issues. The sampling points were distributed along three
 transects in the districts of Alberdi, Guazú-Cuá, San Juan Bautista, and
 Tacuarás Villa Franca and were separated by a minimum distance of 500-600
 m to avoid counting the same individuals twice. Although it was initially
 planned to sample each point count three times, for security reasons 41%
 of the points (11 of 43 points in riparian forest, 14 of 30 in natural
 grasslands, 23 of 50 in savannas and 17 of 35 in anthropized sites) could
 only be sampled twice; the rest were sampled three times. At each point
 count, all birds seen or heard within a radius of 50 m from the center of
 each site within 5 min of arriving at the sample point were counted. Bird
 sampling began at dawn, from 6:00 to 10:00 a.m., and during the afternoon,
 from 4:00 to 7:00 p.m. Of the total of 408 inventories, 143 were carried
 out in the dry season (May-September), and 265 in the wet season
 (October-April). Adverse weather conditions (heavy rains) were avoided,
 and all bird sampling was carried out by the same person (Fátima
 Ortíz).
description: # Bird Abundance Data in the Ñeembucú Wetlands Complex
 [https://doi.org/10.5061/dryad.rfj6q57jq](https://doi.org/10.5061/dryad.rfj6q57jq) ## Description of the data and file structure Ñeembucu_database.xlsx contains the following information: Transect (green column): sampling points were distributed along three transects 8-10 km long (T1, T2, T3) with sampling points being separated by a minimum distance of 500-600 m Habitat (purple column): sampling points were assigned to one of the four dominant habitat types considered in the landscape: riparian forests, natural grasslands, savannas, and anthropized habitats Sampling point (yellow column): ID of the samplin point Period of sampling (blue column): month and year of the sampled inventory Bird abundances (white columns): from Accipiter_bicolor onwards data are the total abundance of birds (number of individuals per species) per inventory. At each inventory, all birds seen or heard within a radius of 50 m from the center of each site within 5 min of arriving were counted. **This dataset contains the data for the article:** Fátima Ortiz, Patricia Salinas, Medes Mendoza, Griselda Zárate, Fátima Piris da Motta, Alberto Esquivel, Karina Núñez, Fernando Silla. 2024. "Diversity and dominance in bird assemblages across habitats in the Ñeembucú Wetlands Complex" to be published in Biotropica. This work was funded by the “Consejo Nacional de Ciencia y Tecnología” (CONACYT) and the “Fondo para la Excelencia de la Educación y la Investigación” (FEEI): Project PINV18-162 "Valoración de los servicios ecosistémicos de la Ecorregión Ñeembucú a través del análisis de la diversidad funcional y taxonómica de las comunidades de fitoplancton, plantas, anfibios y aves". Please, contact authors for reuse of these data. Authors: Fátima Ortiz. Escuela de Biología, Facultad de Ciencias Exactas y Naturales (FACEN), Universidad Nacional de Asunción, Paraguay. [fatimanortiz@gmail.com](mailto:fatimanortiz@gmail.com) Patricia Salinas. Escuela de Biología, Facultad de Ciencias Exactas y Naturales (FACEN), Universidad Nacional de Asunción, Paraguay. [patrisali93@gmail.com](mailto:patrisali93@gmail.com) Medes Mendoza. Escuela de Biología, Facultad de Ciencias Exactas y Naturales (FACEN), Universidad Nacional de Asunción, Paraguay. [medesamg@gmail.com](mailto:medesamg@gmail.com) Griselda Zárate. Escuela de Biología, Facultad de Ciencias Exactas y Naturales (FACEN), Universidad Nacional de Asunción, Paraguay. [grisel.zb@gmail.com](mailto:grisel.zb@gmail.com) Fátima Piris da Motta. Escuela de Biología, Facultad de Ciencias Exactas y Naturales (FACEN), Universidad Nacional de Asunción, Paraguay. fatimapiris92@ gmail.com Alberto Esquivel. Wildlife Paraguay, Benito Juárez, Luque, Paraguay. [alberto.esquivel@wildlife.com.py](mailto:alberto.esquivel@wildlife.com.py) Karina Núñez. Escuela de Biología, Facultad de Ciencias Exactas y Naturales (FACEN), Universidad Nacional de Asunción, Paraguay. [ranitapy@gmail.com](mailto:ranitapy@gmail.com) Fernando Silla. Área de Ecología, Facultad de Biología, Universidad de Salamanca, Spain. [fsilla@usal.es](mailto:fsilla@usal.es)