As people encroach increasingly on natural areas, one question is how this affects avian biodiversity. The answer to this is partly scale-dependent. At broad scales, human populations and biodiversity concentrate in the same areas and are positively associated, but at local scales people and biodiversity are negatively associated with biodiversity. We investigated whether there is also a systematic temporal trend in the relationship between bird biodiversity and housing development. We used linear regression to examine associations between forest bird species richness and housing growth in the conterminous United States over 30 years. Our data sources were the North American Breeding Bird Survey and the 2000 decennial U.S. Census. In the 9 largest forested ecoregions, housing density increased continually over time. Across the conterminous United States, the association between bird species richness and housing density was positive for virtually all guilds except ground nesting birds. We found a systematic trajectory of declining bird species richness as housing increased through time. In more recently developed ecoregions, where housing density was still low, the association with bird species richness was neutral or positive. In ecoregions that were developed earlier and where housing density was highest, the association of housing density with bird species richness for most guilds was negative and grew stronger with advancing decades. We propose that in general the relationship between human settlement and biodiversity over time unfolds as a 2-phase process. The first phase is apparently innocuous; associations are positive due to coincidence of low-density housing with high biodiversity. The second phase is highly detrimental to biodiversity, and increases in housing density are associated with biodiversity losses. The long-term effect on biodiversity depends on the final housing density. This general pattern can help unify our understanding of the relationship of human encroachment and biodiversity response.
File: Pidgeon_etal_ConsBio_2014_0.pdf
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Applications of remote sensing for biodiversity conservation typically rely on image classifications that do not capture variability within coarse land cover classes. Here, we compare two measures derived from unclassified remotely sensed data, a measure of habitat heterogeneity and a measure of habitat composition, for explaining bird species richness and the spatial distribution of 10 species in a semi-arid landscape of New Mexico.We surveyed bird abundance from 1996 to 1998 at 42 plots located in the McGregor Range of Fort Bliss Army Reserve. Normalized Difference Vegetation Index values of two May 1997 Landsat scenes were the basis for among-pixel habitat heterogeneity (image texture), and we used the raw imagery to decompose each pixel into different habitat components (spectral mixture analysis). We used model averaging to relate measures of avian biodiversity to measures of image texture and spectral mixture analysis fractions. Measures of habitat heterogeneity, particularly angular second moment and standard deviation, provide higher explanatory power for bird species richness and the abundance of most species than measures of habitat composition. Using image texture, alone or in combination with other classified imagery-based approaches, for monitoring statuses and trends in biological diversity can greatly improve conservation efforts and habitat management.
File: StLouis_etal_PhilTrns_2014_0.pdf
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Protected areas are a cornerstone for biodiversity conservation, but they also provide amenities that attract housing development on inholdings and adjacent private lands. We explored how this development affects biodiversity within and near protected areas among six ecological regions throughout the United States. We quantified the effect of housing density within, at the boundary, and outside protected areas, and natural land cover within protected areas, on the proportional abundance and proportional richness of three avian guilds within protected areas. We developed three guilds from the North American Breeding Bird Survey, which included Species of Greatest Conservation Need, land cover affiliates (e.g., forest breeders), and synanthropic species associated with urban environments. We gathered housing density data for the year 2000 from the U.S. Census Bureau, and centered the bird data on this year. We obtained land cover data from the 2001 National Land Cover Database, and we used single- and multiple-variable analyses to address our research question. In all regions, housing density within protected areas was positively associated with the proportional abundance or proportional richness of synanthropes, and negatively associated with the proportional abundance or proportional richness of Species of Greatest Conservation Need. These relationships were strongest in the eastern forested regions and the central grasslands, where more than 70% and 45%, respectively, of the variation in the proportional abundance of synanthropes and Species of Greatest Conservation Need were explained by housing within protected areas. Furthermore, in most regions, housing density outside protected areas was positively associated with the proportional abundance or proportional richness of synanthropes and negatively associated with the proportional abundance of land cover affiliates and Species of Greatest Conservation Need within protected areas. However, these effects were weaker than housing within protected areas. Natural land cover was high with little variability within protected areas, and consequently, was less influential than housing density within or outside protected areas explaining the proportional abundance or proportional richness of the avian guilds. Our results indicate that housing development within, at the boundary, and outside protected areas impacts avian community structure within protected areas throughout the United States.
File: Wood_etal_2014_EcoApps.pdf
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Numerous measures of human influence on the environment exist, but one that is of particular importance is houses as they can impact the environment from species through the landscape level. Furthermore, because the addition of houses represents an important component of landscape change, housing information could be used to assess ecological responses (e.g., decline in wildlife habitat) to that change. Recently developed housing density data represents a potential source of information to assess landscape and habitat change over long periods of time and at broad spatial extents, which is critically needed for conservation and management. Considering the potential value of housing data, our goal was to demonstrate how changes in the number of houses leads to changes in the amount of habitat across the landscape, and in-turn, how these habitat changes are likely to influence the distribution and abundance for a species of conservation concern, the Ovenbird (Seiurus aurocapillus). Using a relationship between Ovenbird abundance and housing density, we predict suitable habitat in the forests of Massachusetts (USA) from 1970 to 2030. Over this 60-year period, the number of houses was projected to increase from 1.84 to 3.32 million. This magnitude of housing growth translates into a 57 % decline in Ovenbird habitat (6,002 km2 to 2,616 km2), a minimum decline of ~850,000 (48 %) Ovenbirds, and an increase in the number of subpopulations across the landscape. Overall, housing data provide important information to robustly measure landscape and habitat change, and hence predict population change of a species. We suggest that time series of housing data linked to ecological responses (e.g., Ovenbird abundance) offers a novel and underutilized approach to estimating long-term and spatially broad predictions of ecosystem response to landscape change, which in turn can inform conservation and management.
File: Lepczyk-et-al-2013-HousingDynamics.pdf
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A major challenge for biodiversity conservation is to mitigate the effects of future environmental change, such as land use, in important areas for biodiversity conservation. In the United States, recent conservation efforts by The Nature Conservancy and partners have identified and mapped the nation's Areas of Biodiversity Significance (ABS), representing the best remaining habitats for the full diversity of native species and ecosystems, and thus the most important and suitable areas for the conservation of native biodiversity. Our goal was to understand the potential consequences of future land use changes on the nation's ABS, and identify regions where ABS are likely to be threatened due to future land use expansion. For this, we used an econometric-based model to forecast land use changes between 2001 and 2051 across the conterminous U.S. under alternative scenarios of future land use change. Our model predicted a total of 100,000 to 160,000 km2 of natural habitats within ABS replaced by urban, crop and pasture expansion depending on the scenario (5% to 8% habitat loss across the conterminous U.S.), with some regions experiencing up to 30% habitat loss. The majority of the most threatened ABS were located in the Eastern half of the country. Results for our different scenarios were generally fairly consistent, but some regions exhibited notable difference from the baseline under specific policies and changes in commodity prices. Overall, our study suggests that key areas for conserving United States' biodiversity are likely threatened by future land use change, and efforts trying to preserve the ecological and conservation values of ABS will need to address the potential intensification of human land uses.
File: Martinuzzi_Ecosphere_2013.pdf
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Most of our knowledge of reproduction of wild parrots in the Neotropics comes from studies of tropical lowland species, with few studies addressing species of high-altitude forests. We studied the reproductive biology of Tucuman Parrots (Amazona tucumana) in north-western Argentina between 2004 and 2009. We obtained data on reproductive output for 86 nests and on causes of mortality for 94 nests. Mean clutch-size per nesting attempt was 3.6 eggs 1.0 (s.d.). Hatching success (proportion of eggs laid that hatch) was 0.77 0.17. Fledging success (proportion of nestlings that fledge) was 0.83 0.13. The overall breeding success (mean number of fledglings per laying female per year) was 2.3 0.8. Overall finite nesting success (daily survival rate to the power of the nesting length) was 0.53 0.27, and chick finite nesting success rate was 0.74 0.22. We did not find differences in reproductive rate between Tucuman Parrots and other species of Amazona parrot from lowland habitats. Productivity and nesting success of Tucuman Parrots had high values in some years and low values in others. This was probably related to fruiting events of Podocarpus parlatorei - a critical food item. The main causes of nesting failure were predation (16%) and abandonment (12%). Our results suggest that for several species of Amazona in lowland habitats, predation and poaching may be the main limiting factors whereas climatic factors and food availability may contribute most to nesting failure at higher altitudes.
File: Rivera_etal_2013_Emu.pdf
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California oak savanna is a habitat of sparse tree canopy that extends from northern Baja California to southern British Columbia and is under threat from land-use pressures such as conversion to agriculture, overgrazing, urban development, and fire suppression. Bird-conservation plans have been drafted for the region's oak woodlands. Yet it is unclear whether birds use California oak savanna at different frequencies than they do neighboring oak habitats. In the foothills of the central and northern Sierra Nevada, California, we explored patterns of avian community structure and habitat occupancy in four habitats: blue oak (Quercus douglasii) savanna with a well-developed grass and forb layer, blue oak savanna with a well-developed shrub layer, and two habitats with a denser canopy, blue oak woodland, and montane hardwood. Additionally, we assessed the effect of habitat characteristics on avian community structure and occupancy. Avian communities were uniquely grouped among the four habitats. Five species of management and conservation concern-the Western Kingbird (Tyrannus verticalis), Western Bluebird (Sialia mexicana), Lark Sparrow (Chondestes grammacus), Western Meadowlark (Sturnella neglecta), and Bullock's Oriole (Icterus bullockii)-were predicted to occupy oak savanna habitats at frequencies higher than in oak woodland or montane hardwood. Shrub cover was the most influential habitat characteristic shaping the avian community and was negatively associated with occupancy of the five savanna-affiliated birds. The distinctive structure and occupancy patterns observed for species of concern in California oak savanna suggest that birds perceive this as unique habitat, highlighting the need for its conservation.
File: Wood_etal_Condor2013.pdf
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For decades, ecologists have measured habitat attributes in the field to understand and predict patterns of animal distribution and abundance. However, the scale of inference possible from field measured data is typically limited because large-scale data collection is rarely feasible. This is problematic given that conservation and management typical require data that are fine grained yet broad in extent. Recent advances in remote sensing methodology offer alternative tools for efficiently characterizing wildlife habitat across broad areas. We explored the use of remotely sensed image texture, which is a surrogate for vegetation structure, calculated from both an air photo and from a Landsat TM satellite image, compared with field-measured vegetation structure, characterized by foliage-height diversity and horizontal vegetation structure, to predict avian density and species richness within grassland, savanna, and woodland habitats at Fort McCoy Military Installation, Wisconsin, USA. Image texture calculated from the air photo best predicted density of a grassland associated species, grasshopper sparrow (Ammodramus savannarum), within grassland habitat (R2 = 0.52, p-value ,0.001), and avian species richness among habitats (R2 = 0.54, p-value ,0.001). Density of field sparrow (Spizella pusilla), a savanna associated species, was not particularly well captured by either field-measured or remotely sensed vegetation structure variables, but was best predicted by air photo image texture (R2 = 0.13, p-value = 0.002). Density of ovenbird (Seiurus aurocapillus), a woodland associated species, was best predicted by pixel-level satellite data (mean NDVI, R2 = 0.54, p-value ,0.001). Surprisingly and interestingly, remotely sensed vegetation structure measures (i.e., image texture) were often better predictors of avian density and species richness than field-measured vegetation structure, and thus show promise as a valuable tool for mapping habitat quality and characterizing biodiversity across broad areas.
File: Wood-2013-PLOS-One.pdf
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With limited resources for habitat conservation, the accurate identification of high-value avian habitat is crucial. Habitat structure affects avian biodiversity but is difficult to quantify over broad extents. Our goal was to identify which measures of vertical and horizontal habitat structure are most strongly related to patterns of avian biodiversity across the conterminous United States and to determine whether new measures of vertical structure are complementary to existing, primarily horizontal, measures. For 2,546 North American Breeding Bird Survey routes across the conterminous United States, we calculated canopy height and biomass from the National Biomass and Carbon Dataset (NBCD) as measures of vertical habitat structure and used land-cover composition and configuration metrics from the 2001 National Land Cover Database (NLCD) as measures of horizontal habitat structure. Avian species richness was calculated for each route for all birds and three habitat guilds. Avian species richness was significantly related to measures derived from both the NBCD and NLCD. The combination of horizontal and vertical habitat structure measures was most powerful, yielding high R2 values for nationwide models of forest (0.70) and grassland (0.48) bird species richness. New measures of vertical structure proved complementary to measures of horizontal structure. These data allow the efficient quantification of habitat structure over broad scales, thus informing better land management and bird conservation. Received 10 January 2013, accepted 30 September 2013.
File: culbert-etal-Auk-2013.pdf
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Land use is driven by socio-economic factors that must be understood in order to mitigate habitat loss. Econometric land-use models describe how land use is affected by socio-economic factors, such as financial returns to different uses of land, and they can be linked to biological models to provide new insight for conservation. Our goal was to evaluate the effects of future land use change on the habitat of forest breeding bird species in northern Wisconsin. Specifically, we estimated the effects of land use change on the amount of habitat available and compared the effects of economic policy scenarios on bird habitat. To do this, we coupled a spatially-explicit econometric model of land use change on private lands with models of northern Wisconsin forest bird potential habitat, comparing a 50-yr baseline projection with a scenario providing incentives for forest growth and a high urban growth scenario. The baseline scenario suggests an average of 438,705 ha of forest lost (10%), with 1.9% of that saved under the Forest Incentive scenario, and a 1.6% greater loss for the Urban Growth scenario. Under baseline projections boreal birds experienced the least amount of habitat loss (2-3%), and deciduous forest birds the most (6-8%). For some species, the projected loss of habitat exacerbates ongoing long-term declining population trend. Coupled economic-ecological models can be used to evaluate alternative incentive programs and to explore the complex interactions between policy, land use change, and broad spatial scale ecological processes that are highly relevant to conservation.
File: Beaudry-etal-ConsBio-2013_0.pdf
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