Habitat selection of endemic birds in temperate forests in a biodiversity "Hotspot (original) (raw)
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Biological Conservation, 2005
We show how Chilean forest bird species richness, abundance and guild structure changes as a function of structural properties of forest stands. We surveyed bird assemblages in two old-growth (>200 years), two mid-successional (30–60 years), and two early-successional forest stands (4–20 years), from November 1999 to September 2000, on Chiloé Island, southern Chile (42°S). Birds were grouped into four habitat-use guilds: large-tree users, vertical-profile generalists, understory species, and shrub-users that occasionally use forests. We recorded a total of 24 bird species: 21 in old-growth, 14 in mid-successional and 16 in early-successional stands. Large-tree users and understory birds were most abundant in old-growth stands, vertical-profile generalists were common in both old-growth and mid-successional stands, and shrub-users were only common in early-successional stands. For nine bird species we found significant relationships between their local abundance and forest structural elements. Higher bird densities in old-growth forests were associated with greater availability of canopy emergent trees, snags, logs and understory bamboo cover in this habitat. Accordingly, bird species diversity in forest stands can be predicted by the presence of these structural elements, and forests should be managed to conserve structural elements that create favorable habitat for bird species in order to prevent future species losses due to logging practices.
Community Ecology
Biodiversity conservation requires knowledge about the factors that influence the structure and function of biotic assemblages. In southern Patagonian Nothofagus forests, birds are the most abundant and diverse vertebrates and are known to have different requirements for nesting, breeding and feeding. Therefore, we chose this group to analyze key drivers of avian community dynamics; for conservation purposes, this information is requisite to manage Nothofagus forest landscapes and their associated biota. We first characterized forest structure and understory floristic composition in open and closed canopy broadleaved forests of mixed deciduous (MD) and mixed deciduous-evergreen (MDE) species on the southern coast of Tierra del Fuego National Park, Argentina. For each habitat, bird assemblages were assessed using point counts, checklists and mist-netting. We used ANOVAs and multivariate methods to analyze changes in bird species richness, density, and biomass as a function of habitat and seasonal characteristics. Forest structure and understory plant communities influenced avian assemblage and density; MDE forests had significantly greater species richness, but lower density than MD. Plus, particular species were associated with specific understory conditions, such as Anairetes parulus and Zonotrichia capensis whose presence was related to shrubs. Additionally, variations observed between seasons apparently were related to differential uses of each habitat type during certain times of year. Finally, it was not possible to define a single forest type with greater conservation value for birds; each had a specific bird species assemblage. Consequently, our results suggest the importance of a full representation of habitats to preserve the region’s bird diversity, which also has been described for forest invertebrates and understory plants.
Montane birds are sensitive to a wide variety of human activities, among which climate change is of special concern. Among the most diverse and specialized montane bird communities is that of Polylepis forests in the High Andes (> 3,500 m). Unfortunately, the ecology of birds associated with Polylepis forest, especially endemic and threatened species, remains poorly known. This gap in knowledge is worrisome given that climate models project that future conditions will be warmer and drier, which could negatively impact many of the species in this ecosystem. This research investigated patterns of species richness and bird-habitat relationships across along an elevational gradient (~3,300 – 4,700 m) and across wet-dry seasons in five valleys of Huascaran National Park within the Cordillera Blanca range of Peru. In 2014-2015, birds and habitat characteristics were surveyed at 130 point count locations and systematically observed between points during wet and dry seasons. I calculated observed and expected (Abundance-Coverage Estimator) species richness for valleys, seasons, and within 100-m elevational bands. Estimates of species richness exceed those of previous studies in Polylepis forest along the Andes. There was a consistent pattern of greater species richness in wet compared to dry seasons, though the pattern declined in strength with elevation. Species richness peaked at mid-elevations (~4,000 m) for the overall bird community, while the greatest number of endemics and threatened birds were found at ~4,300 m Polylepis forest was a particularly important habitat that seemed to promote diversity and might provide an important refuge to species in the face of climate change. Species-habitat associations of 50 species of birds, including 13 of conservation priority, showed that birds were associated with four habitat types. Four species of conservation priority (Oreomanes fraseri, Poospiza alticola, Atlapetes rufigenis, and Cranioleuca baroni) were strongly associated with structural characteristics of large forest patches (~10 ha) dominated by P. sericea (<3,800 m), whereas another four (Anairetes alpinus, Leptasthenura yanacensis, Zaratornis stresemanii, and Scytalopus affinis) were associated with less disturbed forests of P. weberbaueri (> 4,200 m). Open Puna and shrubland habitats also maintained a high number of most common species. These results suggest that, although declines in species richness during dry seasons may negatively affect certain species under the projected warmer and drier conditions for this region, Polylepis forest fragments might provide important refuge or buffering against future changes in climate. Moreover, in addition to conserving and using large (>10 ha) P. sericea forests at lower elevations as the cornerstone for maintaining bird diversity, any high elevation (> 4,200 m) relicts of P. weberbaueri, irrespective of size, should be prioritized for conservation in order to protect key habitat of threatened avian species in Cordillera Blanca. Population studies of priority bird species, combined with coordinated monitoring will provide important insights into the response of bird population to human activities and climatic changes and help to inform conservation of High Andean biological diversity.
Biodiversity and Conservation, 2002
We characterize the bird assemblage of an isolated relict temperaterainforest (Santa Inés) in terms of its structure, composition anddynamics. The relict character and long-term isolation of this forest remnant,immersed in a matrix of semiarid scrub, provide a natural experiment to assessthe consequences of long-term isolation and forest area reduction for temperatebird species. Bird surveys were conducted in a forest fragment and thesurrounding scrub matrix between April 1999 (austral autumn) and October 2000(austral spring) on a seasonal basis. Within the forest fragment wedistinguished two microhabitat types: creeks and areas far from creeks (i.e.slopes). A total of 36 species were recorded in the study site, of which 21were inside the relict forest. Highest bird abundance and richness wererecorded during winter and spring, and these were always higher in creek plotsrather than slope plots. Comparisons between this assemblage and thosedistributed in the continuous temperate forest (located more than 900km southwards) indicate that this bird assemblage shares moresimilarities, with regard to bird species composition, to southern temperateforest localities and to other relict forests, than to nearer scrub habitats.However, there are eight species, endemic to temperate forests in southern SouthAmerica, missing from our system. In this regard, our analyses indicate thatthese eight endemic species should be of great conservation concern and willlikely be the ones that will go extinct first if the fragmentation of thetemperate forest continues.
Ecología Austral, 2020
The páramo ecosystem harbors a high concentration of restricted range and threatened bird species. However, human modifications to the high Andean landscape have generated habitat loss and fragmentation throughout this ecosystem. Therefore, protected areas in this region are a priority for biodiversity conservation. Buffer zones around protected areas aim to reduce perturbation within them. However, these areas are still not exempt from sources of stress. We used abundance and diversity of birds, recorded by walking transects, in order to compare the community composition occurring in protected areas and adjacent buffer zones in a hotspot of diversity and endemism: the Macizo del Cajas Biosphere Reserve, in the southern high-Andes of Ecuador. The bird community did not vary in its composition between protected areas and buffer zones. However, the habitat characteristics explained differences in the presence and abundance of trophic guilds. Particularly, increasingly heterogeneous páramo grassland with greater woody plant cover and less intervention explained a greater presence and abundance of more specialized trophic guilds such as nectarivores in shrubs and aerial insectivores in trees and shrubs. We conclude that there are heterogeneous páramo habitats in buffer zones that should be considered in more formal conservation planning to maintain the diversity of specialized birds and therefore functionality of the páramo grassland ecosystem. [Keywords: páramo grassland, Macizo del Cajas Biosphere Reserve, elevation, trophic guilds, specialist birds] R������. La heterogeneidad del hábitat, en lugar de los límites de las áreas protegidas, influye en las comunidades de aves de una reserva de biosfera Andina. El ecosistema de páramo alberga una alta concentración de especies de aves de rango restringido y amenazadas. Sin embargo, las modificaciones humanas al paisaje altoandino han generado pérdida y fragmentación de hábitat en todo este ecosistema. Por lo tanto, las áreas protegidas en esta región son prioritarias para la conservación de la biodiversidad. Las zonas de amortiguamiento en los alrededores de las áreas protegidas tienen por objeto reducir las perturbaciones en éstas; sin embargo, no están exentas de fuentes de estrés. La abundancia y la diversidad de aves, registradas en transectas, se usó para comparar la composición de la comunidad entre áreas protegidas y zonas de amortiguamiento en un hotspot de diversidad y endemismo: la Reserva de la Biósfera del Macizo del Cajas, en los altos Andes del sur del Ecuador. La comunidad de aves no varió en su composición entre las áreas protegidas y las zonas de amortiguamiento. No obstante, las características del hábitat sí explicaron diferencias en la presencia y abundancia de grupos tróficos. En particular, el incremento en la heterogeneidad del páramo, con mayor cobertura de plantas leñosas y menos intervención, explicó una mayor presencia y abundancia de gremios tróficos especializados, tales como nectarívoros en arbustos e insectívoros aéreos en árboles y arbustos. En conclusión, hay hábitats heterogéneos de páramo, en zonas de amortiguamiento, que deben considerarse en una planificación de conservación más formal para mantener la diversidad de aves especialistas y, por lo tanto, la funcionalidad del ecosistema de páramo herbáceo. [Palabras clave: páramo herbáceo, Reserva de la Biósfera Macizo del Cajas, elevación, gremios tróficos, aves especialistas]
Does bird species diversity vary among forest types? A local-scale test in southern Chile
Naturwissenschaften, 2014
Birds are the most diverse vertebrate group in Chile, characterized by low species turnover at the country-size scale (high alpha but low beta diversities), resembling an island biota. We tested whether this low differentiation is valid at a local scale, among six forest habitat types. We detected 25 bird species; avifauna composition was significantly different among habitat types, with five species accounting for 60% of the dissimilarity. We found a higher level of bird assemblage differentiation across habitats at the local scale than has been found at the country-size scale. Such differentiation might be attributed to structural differences among habitats.
Ornithological Applications, 2023
The simplification of forest structural complexity, caused by anthropogenic land-use practices, is one of the main threats to understory specialist birds. We examined the association of both single structural attributes and structural complexity, with the density of 4 understory bird species in the Global Biodiversity Hotspot "Chilean Winter Rainfall-Valdivian Forests" of South America. Between 2011 and 2013, we surveyed habitat attributes and conducted bird point counts in 505 plots in Andean temperate ecosystems in Chile. In each habitat plot, we measured understory density, volume of coarse woody debris (CWD), number of snags, diameter at breast height (DBH) of trees, and leaf litter depth. With these attributes, we developed an index of stand structural complexity (ISC). On average, old-growth forests had higher values for understory density, CWD volume, DBH, and litter depth than secondary forests and open fields, and thus greater values of ISC. The density of understory birds was positively correlated with the ISC for the Rhinocryptidae Pteroptochos tarnii, Scelorchilus rubecula, and Scytalopus magellanicus. We also found a positive association between understory density and litter depth, with the density of the Furnariidae Sylviorthorhynchus desmursii. However, this latter species showed a negative association with the density of snags. Our results suggest the utility of using an index of structural complexity, rather than single or even additive habitat attributes, for determining the density of understory specialist birds. We recommend that management plans should promote the retention of habitat attributes that contribute to the structural complexity of temperate forests of South America and beyond.