1,721,044 research outputs found
Reproductive phenology of the Acadian flycatcher (Empidonax virescens), a Neotropical migratory bird species, across an urban to rural gradient in central Ohio, USA
Get PDFFAES and Human Ecology: 1st Place (The Ohio State University Edward F. Hayes Graduate Research Forum)The tendency for birds to reproduce earlier in the season has been observed in urban compared to rural populations, but these observations are limited primarily to species that spend all or most of the year in North America (i.e., resident or short-distance migrants). However, the factors that influence the reproductive timing of resident and short-distance migrants are unlikely to have the same influence on Neotropical migrants, a group of birds requiring conservation action due to long-term population declines. To understand the relationship between urbanization and reproductive phenology or timing of a Neotropical migratory bird species I (1) described the pattern of reproductive phenology in Neotropical migratory bird species across an urban to rural gradient, (2) assessed the reproductive consequences of varied breeding phenology, and (3) evaluated the extent to which alternative factors might explain differences in reproductive phenology. Data were collected between 2001 and 2007 on 35 different forests spanning an urban to rural gradient in central Ohio, USA. I used Acadian flycatchers (Empidonax virescens) as a model species. Birds were captured, marked, measured, released, and monitored throughout the breeding seasons.
The general pattern of breeding phenology was opposite that found in most resident and short-distance migrant birds. Birds arrived later, initiated clutches later, and finished nesting earlier than birds breeding in more urban forests. The combination of delayed clutch initiation and earlier completion of nesting activity resulted in an abbreviated nesting season associated with urbanization. Ultimately, this attenuated nesting season reduced the number of nests attempted and young produced by urban-breeding birds and shifted the timing of fledging, with the first fledglings being produced relatively later in the breeding season. The underlying causes of the phenological differences are less clear. One possibility supported by my data is that urban forests were disproportionately settled by small females, which initiated their first clutches later in the nesting season than larger females. This study provides the first evidence that urbanization is associated with attenuated nesting seasons for Neotropical migratory birds and that this shift in breeding phenology may have reproductive consequences.A five-year embargo was granted for this item
Temporal variation in the consequences of an exotic shrub on avian nest predation
Get PDF1st Place at the 3rd Annual CFAES Undergraduate Research Forum in the Environmental CategoryExotic plants are recognized as serious threats to biodiversity due to their tendency to disrupt ecosystem processes and alter floristic composition. Recent work also shows exotic plants can influence predator-prey interactions. For example, birds nesting in exotic shrubs such as Lonicera maackii (Amur honeysuckle) and Rosa multiflora (multiflora rose) in urbanized areas are more likely to have their nests depredated than if they nested in native substrates. However, no studies have evaluated whether or not this increased vulnerability to predation varies temporally over the course of a breeding season. Increased predation is especially likely early in the season given that certain exotics, such as Lonicera, show advanced leaf phenology and exhibit full leaf flush long before most other nesting substrates are available to breeding birds. This study tested if the risk associated with nesting in native substrates and two common exotic shrubs varied temporally across the breeding season for a common abundant understory nesting bird, the Northern Cardinal (Cardinalis cardinalis). Logistic exposure models were used to estimate daily nest survival rates of 607 cardinal nests found in riparian forests in central Ohio in 2001-2005. An information-theoretic approach was used to evaluate 4 a priori models explaining variation in daily nest survival. Results indicate that julian date and substrate type (native, Lonicera or Rosa) interacted to influence nest survival. Daily survival rates increased throughout the breeding season for nests in native substrates and Lonicera, whereas daily survival of nests located in Rosa remained more stable throughout the season. Although nests in Rosa were generally more vulnerable to predation than nests in Lonicera, season influenced relative vulnerability. Nests in Lonicera in early spring, prior to leaf emergence of co-dominant plants, showed the lowest rates of daily nest survival of all substrates. Understanding temporal variation in risk to nest predation may elucidate the mechanisms that determine effects of exotic plants on breeding birds. Advisor: Amanda D. RodewaldOhio Division of WildlifeNational Science Foundation (DEB 0340879 to AD Rodewald
Avian bioacoustics in urbanizing landscapes: relationships between urban noise and avian singing behavior
Get PDFWill be presented at the 21st International Bioacoustics Congress in Pavia Italy in September of 2007, then pulished in the proceedings from the congress.Song is a defining characteristic in avian communication systems because of its
role in mate attraction, territory establishment, territory defense, and habitat selection.
Therefore, biologists are increasingly concerned about potential behavioral and
reproductive consequences of anthropogenic noise as it creates novel acoustic
environments for birds. In this study, I examine the extent to which acoustic noise in
urban environments influences the song characteristics and/or singing behavior of
passerines. I predicted that, in response to loud noises, birds may (1) increase singing
rate and/or repetition of songs (including percent of time spent singing), and (2) adjust
song characteristics such as pitch (frequency) and song length. Both of these strategies
have the potential to improve signal transmission by reducing overlap of signals with
ambient noise. Preliminary decibel level data were collected in four a priori
environments to establish the amount of noise disturbance in relation to the type of urban
area. From May – July 2006, song frequency, duration, and singing rate were measured
for 42 Northern Cardinals (Cardinalis cardinalis) and 53 American Robins (Turdus
migratorius) in forests located within these four increasingly louder acoustic
environments (rural to residential, commercial, and highway) in central Ohio. Song
characteristics were digitally measured via computerized spectrogram analysis. As
predicted, frequency range was positively correlated to noise level for both species.
These data suggest that anthropogenic noise may influence avian singing behavior and
therefore has the potential to be a relatively novel selective force in urban areas.NSF, College of Biological
Sciences Scholarship Fund, the USG Academic Enrichment Grant Fund, and the College
of the Arts and Sciences Undergraduate Research Scholarship Fund
Variation in Plumage Coloration of Northern Cardinals in Urbanizing Landscapes
Get PDFDespite decades of study, biologists know relatively little of how one of the most important avian phenotypic signals, feather coloration, may be affected by anthropogenic disturbances resulting from urbanization. From 2006-2008, I examined the relationship between urbanization and the carotenoid-based plumage color in Northern Cardinal (Cardinalis cardinalis) breeding in 13 riparian forests distributed across a rural-to-urban landscape gradient in central Ohio, USA. Color analysis from feathers collected each year from territorial breeding individuals (131 males and 149 females) indicated that plumage had more red hues with improving body condition for males and weakly for females. However, the amount of urbanization surrounding the forests in which cardinals bred was not related to coloration of either males or females. This study provides evidence that male plumage coloration of Northern Cardinals may serve as an effective indicator of individual condition. Also, the lack of a relationship between plumage coloration and urbanization suggests that urbanizing landscapes do not influence the ability of cardinals to sequester carotenoid-rich sources of food.The Ohio State University, College of Biological SciencesThe National Science FoundationNo embarg
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Estructura de la comunidad aviar y uso del hábitat de los bosques de Polylepis a lo largo de un gradiente de elevación
No full textDescargue el texto completo en el repositorio institucional de la Cornell University: https://hdl.handle.net/1813/44286Los bosques de Polylepis son reconocidos como centro de endemismo y diversidad a lo largo de los Andes pero gravemente amenazado por la pérdida de hábitat, la fragmentación y el cambio climático debido a actividades humanas. Censamos aves durante las estaciones seca (mayo-agosto) y húmeda (enero-abril) en 130 puntos distribuidos a lo largo de un gradiente de elevación (3.300–4.700 m) y los analizamos mediante el análisis de correspondencia canónica (CCA). Asociamos 50 especies de aves, incluidas 13 de gran preocupación para la conservación, con cuatro tipos de hábitat básicos: (1) bosques de Polylepis sericea en elevaciones bajas, (2) bosques de P. weberbaueri en elevaciones elevadas, (3) pastizales de Puna. y (4) matorrales. Cuatro especies de prioridad de conservación (e.g Microspingus alticola) se asociaron fuertemente con grandes parches de bosque (∼10-ha) de P. sericea en elevaciones más bajas (4.200 m). Se sugiere: (a) proteger los grandes remanentes (>10 ha) de los bosques de P. sericea en elevaciones más bajas y (b) mantener todos los relictos de P. weberbaueri, independientemente del tamaño, en elevaciones elevadas (>4.200 m).This research investigated patterns of species richness and bird-habitat relationships across along an elevational gradient (~3,300 - 4,700 m) and across wet-dry seasons in five valleys of Huascaran National Park within the Cordillera Blanca range of Peru. In 2014-2015, birds and habitat characteristics were surveyed at 130 point count locations and systematically observed between points during wet and dry seasons. I calculated observed and expected (Abundance-Coverage Estimator) species richness for valleys, seasons, and within 100-m elevational bands. Estimates of species richness exceed those of previous studies in Polylepis forest along the Andes. There was a consistent pattern of greater species richness in wet compared to dry seasons, though the pattern declined in strength with elevation. Species richness peaked at mid-elevations (~4,000 m) for the overall bird community, while the greatest number of endemics and threatened birds were found at ~4,300 m Polylepis forest was a particularly important habitat that seemed to promote diversity and might provide an important refuge for species in the face of climate change. ii Species-habitat associations of 50 species of birds, including 13 of conservation priority, showed that birds were associated with four habitat types. Four species of conservation priority (Oreomanes fraseri, Poospiza alticola, Atlapetes rufigenis, and Cranioleuca baroni) were strongly associated with structural characteristics of large forest patches (~10 ha) dominated by P. sericea ( 4,200 m). Open Puna and shrubland habitats also maintained a high number of most common species. These results suggest that, although declines in species richness during dry seasons may negatively affect certain species under the projected warmer and drier conditions for this region, Polylepis forest fragments might provide important refuge or buffering against future changes in climate. Moreover, in addition to conserving and using large (>10 ha) P. sericea forests at lower elevations as the cornerstone for maintaining bird diversity, any high elevation (> 4,200 m) relicts of P. weberbaueri, irrespective of size, should be prioritized for conservation in order to protect key habitat of threatened avian species in Cordillera Blanca. Population studies of priority bird species, combined with coordinated monitoring, will provide important insights into the response of bird populations to human activities and climatic changes and help to inform conservation of High Andean biological diversity.Estados Unidos. Programa Fulbright. Beca Fulbrigh
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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