Bustard
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Aim With the exception of South Africa there are no systematic, long-term, large-scale bird monitoring programmes in Africa, and for much of the continent the most comprehensive available data for most species are incidental occurrence... more
Aim With the exception of South Africa there are no systematic, long-term, large-scale bird monitoring programmes in Africa, and for much of the continent the most comprehensive available data for most species are incidental occurrence records. Can such data be used to assess range-wide conservation status of widespread low-density species? We examine this using Kori Bustard Ardeotis kori, a large, easily identifiable species with an extensive African range. Location Southern and East Africa, 14 countries. Methods A comprehensive and systematic review of published and unpublished sources provided 1948 unique locality records spanning the years 1863– 2009; these included 410 non-atlas records and 97 historical (pre-1970) records. Range-size changes were examined by comparing minimum convex polygons to quantify Extent of Occurrence pre-and post-1970, and by testing whether more historical records fell outside the recent (post-1970) 95% probability kernel than expected by chance. Additionally, qualitative evidence of changes in abundance was obtained from historical published accounts and contemporary assessments by in-country experts. Results Since the late 19th century, range-size (measured as Extent of Occurrence) has contracted, by 21% in East Africa and 8% in southern Africa. There is strong qualitative evidence of considerable pre-and post-1970 population declines in all range states, except Zambia (slight increase) and Angola (trend unclear). In some countries, declines occurred from the early 1900s. Thus, while relatively modest change in range-size has occurred in over 100 years, numbers have greatly reduced throughout the species' range. Main conclusions Our methodology allowed objective appraisal of continent-wide Kori status. Despite lacking quantitative population estimates and trends, and poor understanding of the species' autecology, common issues for many African species, incidental occurrence records can be used to assess range-wide changes in status. We recommend that this or similar approaches be applied to other widespread low-density species that probably also have rapidly declining populations despite apparently stable range extents.
This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with... more
This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/authorsrights a b s t r a c t We examined whether pastoralism affected the distribution of Asian Houbara Bustard Chlamydotis macqueenii (IUCN Vulnerable) or modified its habitat across 14,500 km 2 of the Kyzylkum Desert, Uzbekistan. In this landscape, sheep grazing is constrained by access to water, allowing effects to be examined independent of topography and vegetation community. Across a gradient of sheep density (0e10 to 30e80 individuals km À2) we achieved n ¼ 140 10-km driven transects (total driven 3500 km). On all transects Houbara and sheep were surveyed at least once, and 96 were driven three times with vegetation sampled on four 50 m-long transects along each of these (measuring 7493 shrubs). Houbara distribution and abundance was also recorded at 147 point counts. In Generalised Linear Models that controlled for plant community, neither interpolated sheep density (within 1 km buffers) nor topographic variation affected houbara incidence on transects, or incidence and abundance at point counts. Although subtle effects were found for some palatable shrubs, sheep did not strongly modify shrub composition or structure at landscape scales. At landscape-scales, livestock browsing has not widely degraded these rangelands, which appear sustainably managed or even under-utilised. Pastoralism and houbara conservation may therefore be compatible, although impacts on nesting females require investigation.
Predictive models can help clarify the distribution of poorly known species but should display strong transferability when applied to independent data. Nevertheless, model transferability for threatened tropical species is poorly studied.... more
Predictive models can help clarify the distribution of poorly known species but should display strong transferability when applied to independent data. Nevertheless, model transferability for threatened tropical species is poorly studied. We built models predicting the incidence of the critically endangered Bengal Florican (Houbaropsis bengalensis) within the Tonle Sap (TLS) floodplain, Cambodia. Separate models were constructed with soil, land-use, and landscape data and species incidence sampled over the entire floodplain (12,000 km 2) and from the Kompong Thom (KT) province (4000 km 2). In each case, the probability of Bengal Florican presence within randomly selected 1 × 1 km squares was modeled by binary logistic regression with multimodel inference. We assessed the transferability of the KT model by comparing predictions with observed incidence elsewhere in the floodplain. In terms of standard model-validation statistics, the KT model showed good spatial transferability. Nevertheless, it overpredicted florican presence outside the KT calibration region, classifying 491 km 2 as suitable habitat compared with 237 km 2 predicted as suitable by the TLS model. This resulted from higher species incidence within the calibration region, probably owing to a program of conservation education and enforcement that has reduced persecution there. Because both research and conservation activity frequently focus on areas with higher density, such effects could be widespread, reducing transferability of predictive distribution models. Generalidad de los Modelos que Predicen la Distribución de Especies: Actividades de Conservación y Reducción de la Transferibilidad del Modelo para una Avutarda Amenazada Resumen: Los modelos predictivos pueden ayudar a clarificar la distribución de especies poco conocidas, pero deben mostrar fuerte transferibilidad cuando se aplican a datos independientes. Sin embargo, la trans-feribilidad del modelo para especies tropicales amenazadas está poco estudiada. Construimos modelos para predecir la incidencia de Houbaropsis bengalensis, críticamente en peligro en la llanura aluvial Tonle Sap, Camboya. Construimos modelos separados con datos de suelo, uso de suelo y del paisaje y de la incidencia de la especie obtenidos en toda la llanura aluvial (12,000 km 2) y de la provincia Kompong Thom (4000 km 2). En cada caso, se modeló la probabilidad de la presencia de H. bengalensis en cuadrantes de 1 × 1 km mediante regresión logística binaria con inferencia de modelos múltiples. Evaluamos la transferibilidad del modelo de † †Current address: WWF Greater Mekong, Cambodia Country Programme,