Occupancy

About: Occupancy is a research topic. Over the lifetime, 2757 publications have been published within this topic receiving 68288 citations.

Use of multispecies occupancy models to evaluate the response of bird communities to forest degradation associated with logging.

Abstract: Forest degradation is arguably the greatest threat to biodiversity, ecosystem services, and rural livelihoods. Therefore, increasing understanding of how organisms respond to degradation is essential for management and conservation planning. We were motivated by the need for rapid and practical analytical tools to assess the influence of management and degradation on biodiversity and system state in areas subject to rapid environmental change. We compared bird community composition and size in managed (ejido, i.e., communally owned lands) and unmanaged (national park) forests in the Sierra Tarahumara region, Mexico, using multispecies occupancy models and data from a 2-year breeding bird survey. Unmanaged sites had on average higher species occupancy and richness than managed sites. Most species were present in low numbers as indicated by lower values of detection and occupancy associated with logging-induced degradation. Less than 10% of species had occupancy probabilities >0.5, and degradation had no positive effects on occupancy. The estimated metacommunity size of 125 exceeded previous estimates for the region, and sites with mature trees and uneven-aged forest stand characteristics contained the highest species richness. Higher estimation uncertainty and decreases in richness and occupancy for all species, including habitat generalists, were associated with degraded young, even-aged stands. Our findings show that multispecies occupancy methods provide tractable measures of biodiversity and system state and valuable decision support for landholders and managers. These techniques can be used to rapidly address gaps in biodiversity information, threats to biodiversity, and vulnerabilities of species of interest on a landscape level, even in degraded or fast-changing environments. Moreover, such tools may be particularly relevant in the assessment of species richness and distribution in a wide array of habitats. Uso de Modelos de Ocupacion para Multiples Especies para Evaluar la Respuesta de las Comunidades de Aves a la Degradacion de Bosques Asociada con la Tala

Avian occupancy response to oak woodland and savanna restoration

Abstract: Oak (Quercus spp.) woodlands and savannas throughout the Mid-South, USA have become closed-canopy forests through succession in the absence of fire, contributing to declines in disturbance-dependent avian species. Restoration could ameliorate these trends, but effects of such management practices on avian communities of the Mid-South are poorly understood. We implemented an experiment on the Cumberland Plateau, Tennessee with treatments involving fall (Oct) or spring (Mar) fire with woodland (14 m2/ha) or savanna (7 m2/ha) residual basal area and unmanaged control stands (20 ha each). We conducted fixed-radius point counts 3 times annually (2010–2012) and analyzed trends in naive occupancy for 41 species. For 20 species with adequate data (10 early-, 10 late-successional), we performed multiple-season, robust-design occupancy modeling and accounted for detection bias. We then used mixed-model polynomial regression to define relationships between occupancy and measures of live and dead basal area, midstory density, and herbaceous groundcover. Restoration substantially altered forest structural characteristics but did not affect the occupancy of most late-successional species. In contrast, the presence of early-successional species increased as live basal area decreased and herbaceous groundcover increased. Only 3 of 41 species (hooded warbler [Setophaga citrina], ovenbird [Seiurus aurocapilla], and worm-eating warbler [Helmitheros vermivorum]) exhibited reduced occupancy as woodland and savanna conditions were approached. The presence of all other species, including 13 regionally and 2 continentally declining, remained constant or increased as restoration progressed. Woodland conditions of 10 m2/ha live basal area and 20% herbaceous groundcover maximized occupancy of early-successional species with little consequences for late-successional species. Proceeding further toward savanna conditions negatively affected species associated with lower strata of mature-forests but further increased the presence of some early-successional species. Midstory density and dead basal area were poor predictors of occupancy and thus may be necessary but not sufficient in promoting early-successional species. Our results suggest implementing oak woodland and savanna management in the Mid-South could benefit disturbance-dependent birds of high conservation priority with minimal negative impacts on the presence of late-successional species. © 2016 The Wildlife Society.

Forest habitats in a mixed urban-agriculture mosaic landscape: patterns of mammal occupancy

Abstract: Conservation planning for biodiversity within anthropogenic landscapes is crucial given the rate of habitat conversion and human population growth. Investigating anthropogenic impacts on the persistence of biodiversity is key to management decision-making. We investigated the influence of protected areas (PAs), agriculture and urbanisation on the occupancy of mammal communities in an anthropogenic matrix containing indigenous forest fragments of the Coastal Belt of southern KwaZulu-Natal, South Africa. We integrated camera-trap mammal data, land-use and human population density within occupancy models, and compared occupancy of individual species across the land-use mosaic. We modelled occupancy of seven mammal species with sufficient naive occupancy (> 0.20, range 0.25–0.87). The occupancy of Philantomba monticola was positively influenced by human population size and was higher within urban areas compared with PAs. Although human population size positively affected Hystrix africaeaustralis occupancy, it along with Atilax paludinosus had a lower occupancy within urban areas. Tragelaphus scriptus and Potamochoerus larvatus overall had higher and Sylvicapra grimmia had lower occupancies within PAs. Species were variable in their response to the anthropogenic changes in the landscape. For example, occupancy of P. monticola was low within PAs but high in areas where change in land ownership and loss of habitat are threats. For other species, it appeared that the density of infrastructure of the urban landscape, rather than human population density, affected them negatively. However, seasonal differences within different management regimes also provided context-specific influences on occupancy and detectability. We emphasize the importance of natural vegetation patches within anthropogenic landscapes for maintaining native fauna, whilst stressing the value of temporally replicated, multi-species, regional-scale studies when making conservation decisions.

Habitat Associations of Secretive Marsh Birds in Iowa

Abstract: Drastic losses of wetland habitats across North America over the past century have resulted in population declines of many marsh birds therefore emphasizing the need for proper management of remaining wetlands for the conservation of marsh birds. Our objective was to evaluate the probability of site occupancy of secretive marsh birds in Iowa in response to habitat variables at multiple scales. We conducted call-broadcast surveys for eight species of marsh birds at wetlands in Iowa from 16 May–15 July 2009 and from 20 April–10 July 2010. We utilized occupancy models in Program MARK to estimate site occupancy probability based on habitat covariates for four species with the most detections (Pied-billed Grebe [Podilymbus podiceps], Least Bittern [Ixobrychus exilis], Virginia Rail [Rallus limicola], and Sora [Porzana carolina]). Wetland size had a positive effect on site occupancy for Least Bitterns, water depth positively affected site occupancy for Pied-billed Grebes and Least Bitterns, and percent cover of cattail positively affected site occupancy for Virginia Rails. Knowing habitat associations of secretive marsh birds in Iowa will allow us to provide guidance on wetland restoration and management decisions that will aid the conservation of these birds.