Trends in the mid-continent population of sandhill cranes (Grus canadensis) indicate that the species is increasing. A large proportion of this population winters in northern Mexico where possible conflicts between local inhabitants and cranes can occur. We conducted interviews of 40 rural inhabitants living near wetlands used by cranes in three Mexican states. All interviewees had knowledge of cranes and were capable of describing them. The arrival of cranes affected 43% of interviewees. The negative effects were mainly destroyed crops with a subsequent diminished production. Seventy percent of those affected implemented scare tactics to deter the birds, while others (15%) did nothing to mitigate crop losses and accepted such damages. While sandhill cranes continue to increase, conflicts with humans are expected to rise. Our results provide information about human attitudes toward cranes and can serve as the basis for future conservation guidelines.
Breeding-season productivity (the per capita number of offspring surviving to the end of the breeding season) is seldom estimated for multibrooded songbirds because of cost and logistical constraints. However, this parameter is critical for predictions of population growth rates and comparisons of seasonal productivity across geographic or temporal scales. We constructed a dynamic, stochastic, individual-based model of breeding-season productivity using demographic data from Wood Thrushes (Hylocichla mustelina) in central Georgia from 1993 to 1996. The model predicts breeding-season productivity as a function of adult survival, juvenile survival, nesting success, season length, renesting interval, and juvenile-care intervals. The model predicted that seasonal fecundity (number of fledglings produced) was 3.04, but only 2.04 juveniles per female survived to the end of the breeding season. Sensitivity analyses showed that differences in renesting interval, nesting success, fledglings per successful nest, and adult and juvenile survival caused variation in breeding-season productivity. Contrary to commonly held notions, season length and fledgling-care interval length did not cause variation in breeding-season productivity. This modeling exercise emphasizes the need for demographic data for songbird species, and we encourage biologists to use similar models to evaluate productivity in songbird populations.
Historically, eastern ponderosa pine (Pinus ponderosa) forests were described as sparse patches of old-growth trees maintained by frequent, low-severity fires; however, in recent decades, there have been a number of large mixed-severity wildfires throughout the range of these forests. Wildlife responses to severe fire disturbance in eastern ponderosa pine forests are not well understood. Our study investigates how cavity-nesting bird species in an eastern ponderosa pine forest are impacted by burn severity. The objectives of our study were to: (1) identify the community composition of cavity-nesting birds in a 27 y old burn of mixed severity, (2) assess how habitat variables important to cavity-nesting birds differ in the mixed-severity fire, and (3) determine what habitat variables best predict bird occurrence 27 y after mixed-severity fire. We surveyed 56 sites across four burn severity classes, ranging from unburned to severely burned forest, in the Pine Ridge region of Nebraska. We measured multiple habitat characteristics (tree and snag diameter at breast height (DBH), coarse woody debris (CWD), tree and snag density, shrub height, and shrub cover) in May–August 2016 and conducted bird count surveys between 25 May and 8 June 2016. Cavity-nesting bird species' occurrence varied among the burn severity variables. Burn severity class (unburned, low severity, moderate severity, high severity) was a significant predictor of habitat characteristics for cavity-nesting birds, including tree density, snag density, mean snag DBH, variance in DBH, and CWD, which also was the best indicator of cavity-nesting bird community composition. We report evidence that mixed-severity wildfires in eastern ponderosa pine forests create variation in habitat characteristics and cavity-nesting bird occurrence.
We used traditional searching, as well as radio-telemetry, to find 125 Wood Thrush (Hylocichla mustelina) nests during 1994–1996 at the Piedmont National Wildlife Refuge in Georgia, USA. We compared daily nest survival rates for 66 nests of radio-marked birds with 59 nests of birds found through systematic searching. By using radio-telemetry, we found Wood Thrush nests in higher elevation pine habitats, in addition to the more usual hardwood forests with moist soils. We found nests of radio-marked birds farther from streams than nests found by systematic searching. Thirty-two percent of radio-marked birds' nests were found at the tops of slopes, compared to 15% of the nests found by traditional searching. In addition, radio-marked birds generally moved up-slope for re-nesting attempts. Although the distribution of nests found with telemetry and searching varied, daily nest survival did not vary between the two groups. Radio-telemetry provided new information about Wood Thrush nesting habitats. We believe radio-telemetry can be a valuable addition to traditional searching techniques; it has the potential to provide a sample of nests free from a priori habitat biases.
After a well-documented recovery following substantial population declines throughout most of North America, the Peregrine Falcon (Falco peregrinus) was delisted under provisions of the Endangered Species Act in 1999. Post-delisting monitoring for the Peregrine Falcon stipulated surveys of breeding locations and did not specifically emphasize other metrics of population dynamics such as survival. We used banding data from Peregrine Falcons captured on the Washington coast during 1212 vehicle surveys between 1995 and 2018 to assess apparent survival and resighting frequencies. Our mark-recapture data set included 226 Peregrine Falcons: 148 females and 78 males. Fourteen Peregrine Falcons were recovered dead and another eight were found injured or uninjured and unable to fly due to illness or substantially soiled feathers. We had 744 resightings, 67.1% (n = 499) by our research group during surveys (Group A) and 32.9% (n = 245) by others (Group B). We found a dramatic increase in Group B contributions beginning in 2008 due to the emergence of digital camera use in wildlife photography and increased public awareness of our project. Data from 1995 to 2018 supported the estimation of apparent survival for three age classes of Peregrine Falcons: 0.424 (SE = 0.057) for hatch-year (<1 yr old); 0.663 (SE = 0.066) for second-year (1–2 yr old), and 0.738 (SE = 0.030) for after-second-year (>2 yr old). Our long-term mark-resighting analyses of overwintering and migratory Peregrine Falcons along the Washington coast provide evidence of a reasonably high level of apparent survival that suggests good population performance.
Biologists commonly use multistate capture-recapture models to estimate movement and survival rates of animals. Recent improvements to genetic and stable-isotope techniques have created the potential for making a posteriori determinations of an animal's location. Here, I present a new multistate model structure that incorporates captured animals' backdated locations. To provide data for this model, I developed a computer simulation in which birds moved between two geographic strata during three time periods. Birds were captured and assigned mortality, and multistate capture histories were recorded. I enhanced capture histories for birds using data from simulated stable-isotope analyses. I then used the modified multistate model to estimate survival, movement, and recapture probabilities. I evaluated the ability of stable-isotope data to more precisely estimate movement over a range of recapture and movement rates. In each of nine simulations, information from stable isotopes improved the precision of the movement estimate; estimates and precision of survival and recapture rates did not change. As real stable-isotope data sets become available, this estimation model may be useful to biologists interested in improving precision of movement rates among geographic strata. Un Modelo Multi-Estado de Captura-Recaptura Usando Clasificación A Posteriori para Potenciar la Estimación de Tasas de Movimiento Resumen. Los biólogos usan generalmente modelos multi-estado de captura-recaptura para estimar las tasas de movimiento y supervivencia de los animales. Las mejoras recientes de las técnicas genéticas y de isótopos estables han creado el potencial de hacer determinaciones a posteriori de la localización de un animal. Aquí presento la estructura de un nuevo modelo multi-estado que incorpora las localidades pasadas de animales capturados. Para contar con datos para este modelo, desarrollé una simulación en computadora en la cual las aves se movieron entre dos estratos geográficos durante tres períodos de tiempo. Las aves fueron capturadas y se les asignó un valor de mortalidad, y se registraron las historias de capturas multi-estado. Potencié el uso de las historias de captura de las aves empleando datos simulados de análisis de isótopos estables. Luego usé el modelo multi-estado modificado para estimar las probabilidades de supervivencia, de movimiento y de recaptura. Evalué la habilidad de los datos de isótopos estables para estimar movimiento de modo más preciso en un rango de tasas de recaptura y movimiento. En cada una de las nueve simulaciones, la información de los isótopos estables mejoró la precisión de la estimación de movimiento; las estimaciones y la precisión de las tasas de supervivencia y recaptura no variaron. A medida que estén disponibles datos reales de isótopos estables, este modelo de estimación puede ser útil para los biólogos interesados en mejorar la precisión de las tasas de movimiento entre estratos geográficos.
Abstract Harnessing energy for cooking, heating, eating, and travel is a fundamental human requirement and, prior to fossil fuel adoption, much energy was derived from local landscapes. In the North American Great Plains, the nineteenth century was a period of rapid social-ecological change, and adaptive fuel procurement was at its core. Here, we review nineteenth-century accounts of energy acquisition and use in Great Plains landscapes, documenting the utilities, renewabilities and geographic distributions of important organic fuels, excluding coal. Native and Euro-Americans devised and adopted diverse strategies for accessing energy stored in herbaceous biomass and woody biomass, which, although variable in form, availability, specific energy and energy density, could generally be obtained locally and regenerate relatively quickly. Three forms of herbaceous biomass - forage (undigested), buffalo chips (partially digested) and pemmican (metabolized) - were associated with ubiquity of prairie vegetation and bison, whereas woody biomass was a rarer fuel largely restricted to lowlands and decreasing from east to west. Amidst transformational waves of colonisation in dynamic environments, seasonal strategies for securing energy locally were supplanted by strategies of fuel storage and importation. All fuel-based adaptations had social-ecological causes and consequences and, in nineteenth century plains landscapes, colonisation facilitated rapid, cross-cultural exchanges of fuel sources, technologies, strategies for increasing energy access and human environmental influences that collectively shaped regional environmental history.
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