Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols Used xiii 1. The Importance of Islands 3 2. Area and Number of Speicies 8 3. Further Explanations of the Area-Diversity Pattern 19 4. The Strategy of Colonization 68 5. Invasibility and the Variable Niche 94 6. Stepping Stones and Biotic Exchange 123 7. Evolutionary Changes Following Colonization 145 8. Prospect 181 Glossary 185 References 193 Index 201

The Theory of Island Biogeography

Precision agriculture (PA) is the application of geospatial techniques and sensors (e.g., geographic information systems, remote sensing, GPS) to identify variations in the field and to deal with them using alternative strategies. In particular, high-resolution satellite imagery is now more commonly used to study these variations for crop and soil conditions. However, the availability and the often prohibitive costs of such imagery would suggest an alternative product for this particular application in PA. Specifically, images taken by low altitude remote sensing platforms, or small unmanned aerial systems (UAS), are shown to be a potential alternative given their low cost of operation in environmental monitoring, high spatial and temporal resolution, and their high flexibility in image acquisition programming. Not surprisingly, there have been several recent studies in the application of UAS imagery for PA. The results of these studies would indicate that, to provide a reliable end product to farmers, advances in platform design, production, standardization of image georeferencing and mosaicing, and information extraction workflow are required. Moreover, it is suggested that such endeavors should involve the farmer, particularly in the process of field design, image acquisition, image interpretation and analysis.

The application of small unmanned aerial systems for precision agriculture: a review

Migratory bird needs must be met during four phases of the year: breeding season, fall migration, wintering, and spring migration; thus, management may be needed during all four phases. The bulk of research and management has focused on the breeding season, although several issues remain unsettled, including the spatial extent of habitat influences on fitness and the importance of habitat on the breeding grounds used after breeding. Although detailed investigations have shed light on the ecology and population dynamics of a few avian species, knowledge is sketchy for most species. Replication of comprehensive studies is needed for multiple species across a range of areas, Information deficiencies are even greater during the wintering season, when birds require sites that provide security and food resources needed for survival and developing nutrient reserves for spring migration and, possibly, reproduction. Research is needed on many species simply to identify geographic distributions, wintering sites, habitat use, and basic ecology. Studies are complicated, however, by the mobility of birds and by sexual segregation during winter. Stable-isotope methodology has offered an opportunity to identify linkages between breeding and wintering sites, which facilitates understanding the complete annual cycle of birds. The twice-annual migrations are the poorest-understood events in a bird's life. Migration has always been a risky undertaking, with such anthropogenic features as tall buildings, towers, and wind generators adding to the risk. Species such as woodland specialists migrating through eastern North America have numerous options for pausing during migration to replenish nutrients, but some species depend on limited stopover locations. Research needs for migration include identifying pathways and timetables of migration, quality and distribution of habitats, threats posed by towers and other tall structures, and any bottlenecks for migration. Issues such as human population growth, acid deposition, climate change, and exotic diseases are global concerns with uncertain consequences to migratory birds and even less-certain remedies. Despite enormous gaps in our understanding of these birds, research, much of it occurring in the past 30 years, has provided sufficient information to make intelligent conservation efforts but needs to expand to handle future challenges.

/pdf/conserving-migratory-land-birds-in-the-new-world-do-we-know-2adovih86l.pdf

Conserving migratory land birds in the new world: do we know enough?

Detailed empirical models predicting both species occurrence and fitness across a landscape are necessary to understand processes related to population persistence Failure to consider both occurrence and fitness may result in incorrect assessments of habitat importance leading to inappropriate management strategies We took a two-stage approach to identifying critical nesting and brood-rearing habitat for the endangered Greater Sage-Grouse (Centrocercus urophasianus) in Alberta at a landscape scale First, we used logistic regression to develop spatial models predicting the relative probability of use (occurrence) for Sage-Grouse nests and broods Secondly, we used Cox proportional hazards survival models to identify the most risky habitats across the landscape We combined these two approaches to identify Sage-Grouse habitats that pose minimal risk of failure (source habitats) and attractive sink habitats that pose increased risk (ecological traps) Our models showed that Sage-Grouse select for heterogeneous patches of moderate sagebrush cover (quadratic relationship) and avoid anthropogenic edge habitat for nesting Nests were more successful in heterogeneous habitats, but nest success was independent of anthropogenic features Similarly, broods selected heterogeneous high-productivity habitats with sagebrush while avoiding human developments, cultivated cropland, and high densities of oil wells Chick mortalities tended to occur in proximity to oil and gas developments and along riparian habitats For nests and broods, respectively, approximately 10% and 5% of the study area was considered source habitat, whereas 19% and 15% of habitat was attractive sink habitat Limited source habitats appear to be the main reason for poor nest success (39%) and low chick survival (12%) Our habitat models identify areas of protection priority and areas that require immediate management attention to enhance recruitment to secure the viability of this population This novel approach to habitat-based population viability modeling has merit for many species of concern

/pdf/linking-occurrence-and-fitness-to-persistence-habitat-based-3d74a8b5cn.pdf

Linking occurrence and fitness to persistence: habitat-based approach for endangered greater sage-grouse.

Conservation of Grassland Birds in North America: Understanding Ecological Processes in Different Regions, Report of the AOU Committee on Conservation

Grasslandfragmentation and habitat loss are hypothesized to be contributing to widespread grass- land bird declines in North America due to the adverse effects offragmentation on breeding bird abundance and reproductive success. To assess the effects offragmentation on the reproductive success of grassland birds, we measured rates of nest predation and brood parasitism for four species of birds (Grasshopper Sparrow (Ammodramus savannarum, Henslow's Sparrow/Ammodramus henslowiij, Eastern Meadowlark (Stumella magna), and Dickcissel (Spiza Americana)) in 39 prairie fragments ranging from 24 to >40,000 ha in size in five states in the mid-continental United States. Throughout the region, nest-predation rates were significantly in- fluenced by habitatfragmentation. Nest predation was highest in small ( 1000 ha) prairie fragments. Rates of brood parasitism by Brown-headed Cowbirds (Molothrus ater), how- ever, were not consistently related to fragment size and instead were more strongly related to regional cowbird abundance, being significantly higher in regions with high cowbird abundance. Differences in nest-predation rates between large fragments (54-68% of all nests lost to predators) and small fragments (78-84% lost to predators) suggest that fragmentation of prairie habitats may be contributing to regional declines of grass- land birds. Maintaining grassland bird populations, therefore, may require protection and restoration of large prairie areas.

/pdf/effects-of-prairie-fragmentation-on-the-nest-success-of-363mp3xagt.pdf

Effects of prairie fragmentation on the nest success of breeding birds in the midcontinental United States

https://www.fws.gov/southwest/es/documents/R2ES/LitCited/LPC_2012/With_et_al_2008.pdf

Remaining large grasslands may not be sufficient to prevent grassland bird declines

The northern bobwhite (Colinus virginianus) is an economically important gamebird that is currently undergoing widespread population declines. Despite considerable research on the population ecology of bobwhites, there have been few attempts to model population dynamics of bobwhites to determine the contributions of different demographic parameters to variance of the finite rate of population change (λ). We conducted a literature review and compiled 405 estimates of 9 demographic parameters from 49 field studies of bobwhites. To identify demographic parameters that might be important for management, we used life-stage simulation analyses (LSA) to examine sensitivity of λ to simulated variation in 9 demographic parameters for female bobwhites. In a baseline LSA based on uniform distributions bounded by the range of estimates for each demographic parameter, bobwhite populations were predicted to decline (λ = 0.56) and winter survival of adults made the greatest contribution to variance of λ (r2 = 0...

Demographic Sensitivity of Population Change in Northern Bobwhite

: Extensive habitat loss and changing agricultural practices have caused widespread declines in grassland birds throughout North America. The Flint Hills of Kansas and Oklahoma—the largest remaining tallgrass prairie—is important for grassland bird conservation despite supporting a major cattle industry. In 2004 and 2005, we assessed the community, population, and demographic responses of grassland birds to the predominant management practices (grazing, burning, and haying) of the region, including grasslands restored under the Conservation Reserve Program (CRP). We targeted 3 species at the core of this avian community: the Dickcissel (Spiza americana), Grasshopper Sparrow (Ammodramus savannarum), and Eastern Meadowlark (Sturnella magna). Bird diversity was higher in native prairie hayfields and grazed pastures than CRP fields, which were dominated by Dickcissels. Although Dickcissel density was highest in CRP, their nest success was highest and nest parasitism by Brown-headed Cowbirds (Moluthrus ater) lowest in unburned hayfields (in 2004). Conversely, Grasshopper Sparrow density was highest in grazed pastures, but their nest success was lowest in these pastures and highest in burned hayfields, where cowbird parasitism was also lowest (in 2004). Management did not influence density and nest survival of Eastern Meadowlarks, which were uniformly low across the region. Nest success was extremely low (5–12%) for all 3 species in 2005, perhaps because of a record spring drought. Although the CRP has benefited grassland birds in agricultural landscapes, these areas may have lower habitat value in the context of native prairie. Hayfields may provide beneficial habitat for some grassland birds in the Flint Hills because they are mowed later in the breeding season than elsewhere in the Midwest. Widespread grazing and annual burning have homogenized habitat—and thus grassland-bird responses—across the Flint Hills. Diversification of management practices could increase habitat heterogeneity and enhance the conservation potential of the Flint Hills for grassland birds.




Resumen: La perdida de habitat y el cambio de practicas agricolas han causado declinaciones generalizadas en las aves de pastizal en toda Norte America. Las Flint Hills en Kansas y Oklahoma—el remanente mas extenso de tallgrass prairie—son importantes para la conservacion de aves de pastizal no obstante que soporta una importante industria ganadera. En 2004 y 2005, evaluamos las respuestas de la comunidad, poblacion y demografia de aves de pastizal a las practicas de manejo predominantes (pastoreo, quema y almiar) en la region, incluyendo pastizales restaurados bajo el Programa de Conservacion de Reservas (PCR). Nos centramos en tres especies en el nucleo de esta comunidad de aves: Spiza americana, Ammodramus savannarum y Sturnella magna. La diversidad de aves fue mayor en las praderas nativas y en los pastizales pastoreados que en los campos del PCR, que fueron dominados por S. americana. Aunque la densidad de S. americana fue mayor en PCR, su exito de nidacion fue mayor y el parasitismo de nidos por Molothrus ater fue menor en las tierras no quemadas (en 2004). Por el contrario, la densidad de A. savannarum fue mayor en los pastizales pastoreados, pero su exito de nidacion fue menor en estos pastizales y mayor en los pastizales quemados, donde el parasitismo tambien fue menor (en 2004). El manejo no influyo en la densidad y supervivencia de nidos de S. magna, que fueron bajas en toda la region. El exito de nidacion fue extremadamente bajo (5–12%) en las tres especies en 2005, quizas debido a una sequia primaveral sin precedente. Aunque el PCR ha beneficiad a las aves en paisajes agricolas, estas areas pueden tener menor valor de habitat en el contexto de la pradera nativa. Los terrenos con almiar pueden proporcionar habitat benefico a algunas aves de pastizal las Flint Hill porque son segados al final de la epoca reproductiva. El pastoreo extensivo y las quemas anuales han homogeneizado el habitat—y por lo tanto las respuestas de las aves de pastizal—en las Flint Hills. La diversificacion de las practicas de manejo podria incrementar la heterogeneidad del habitat y resaltar el potencial de conservacion de las Flint Hills para las aves de pastizal.

William E. Jensen

Papers

Effects of prairie fragmentation on the nest success of breeding birds in the midcontinental United States

Remaining large grasslands may not be sufficient to prevent grassland bird declines

Demographic Sensitivity of Population Change in Northern Bobwhite

Grassland Bird Responses to Land Management in the Largest Remaining Tallgrass Prairie

Eastern Meadowlark (Sturnella magna)