1,721,001 research outputs found
Patch scale nest-site selection by Marbled Murrelets (Brachyramphus marmoratus)
Get PDFThe Marbled Murrelet (Brachyramphus marmoratus) is a threatened alcid that nests almost exclusively in old-growth forests along the Pacific coast of North America. Nesting habitat has significant economic importance. Murrelet nests are extremely difficult and costly to find, which adds uncertainty to management and conservation planning. Models based on air photo interpretation of forest cover maps or assessments by low-level helicopter flights are currently used to rank presumed Marbled Murrelet nesting habitat quality in British Columbia. These rankings are assumed to correlate with nest usage and murrelet breeding productivity. Our goal was to find the models that best predict Marbled Murrelet nesting habitat in the ground-accessible portion of the two regions studied. We generated Resource Selection Functions (RSF) using logistic regression models of ground-based forest stand variables gathered at plots around 64 nests, located using radio-telemetry, versus 82 random habitat plots. The RSF scores are proportional to the probability of nests occurring in a forest patch. The best models differed somewhat between the two regions, but include both ground variables at the patch scale (0.2-2.0 ha), such as platform tree density, height and trunk diameter of canopy trees and canopy complexity, and landscape scale variables such as elevation, aspect, and slope. Collecting ground-based habitat selection data would not be cost-effective for widespread use in forestry management; air photo interpretation and low-level aerial surveys are much more efficient methods for ranking habitat suitability on a landscape scale. This study provides one method for ground-truthing the remote methods, an essential step made possible using the numerical RSF scores generated herein.Peer reviewedfinal article publishedBrachyramphus marmoratusResource Selection Functionsnesting habitatMarbled Murrelethabitat selectio
Marbled murrelets select distinctive nest trees within old-growth forest patches
Get PDFThe coastal old-growth forests of North America’s Pacific Coast are renowned both for their commercial and ecological value. This study adds to growing evidence that selective harvesting of the largest trees may have a disproportionate ecological impact. Marbled Murrelets (Brachyramphus marmoratus), a threatened species, nest almost exclusively in these old-growth forests. Detailed knowledge of nesting habitat selection provides guidance for habitat management and conservation. Habitat selection for this species has been studied at a variety of scales using ground and remote methods. However, because Marbled Murrelet nesting activity is limited to a single mossy platform on a single tree, we investigated nest tree selection within old-growth forest patches, using a set of 59 forest patches containing active nests. Nest trees were usually distinctive compared with neighboring trees in the surrounding 25 m radius patch. They averaged 15 to 20% taller than neighboring trees depending on region, had significantly larger stem diameters, more potential nesting platforms, and more moss. They had the most extreme values of height and width about three times as often as expected by chance. An analysis of moss platform use as a function of number of platforms per platform tree suggests that murrelets select individual platforms, rather than platform trees per se. Nonetheless, highly selective logging practices that remove high-value trees from stands may also remove trees most likely to be selected by nesting murrelets.Peer reviewedfinal article publishedBrachyramphus marmoratusnest treeMarbled Murrelethabitat selectionBritish Columbi
Dynamics, genetic structure and viability of a small and declining Temminck's stint (<em>Calidris temminckii</em>) population
Get PDFAbstractGlobally, populations of several wader species are in decline. However, for most populations, information on abundance, its changes and the causes of declines is insufficient for designing successful management strategies to recover threatened populations. In this thesis I studied the status and population trends, nesting success, genetic structure and viability of a small, declining and threatened Temminck’s stint population in the Bothnian Bay in the northern Baltic Sea. Historical population data, recent population counts in the early 1990s and in 1999–2002 and the demographic data showed that the decline is continuing, paralleled by declines in nesting success, recruitment and adult survival.Decline in nesting success was caused by a coincident increase in nest predation. Depredation was the main cause of nest losses. The common gull (Larus canus) and the ruddy turnstone (Arenaria interpres) were found to be the most important nest predators. I tested if an increase in nest concealment and consequent decrease in visibility lowers the efficiency of the early-departure antipredator behaviour of the species. An expected positive correlation emerged between visibility and flushing distance in the presence of alarm-giving birds, but not without them. This indicates that Temminck’s stint exploits signals from other birds as early warning of an approaching predator. More nests were lost to predation on narrow than on wide shores. The nest predation rate was not related to habitat (natural vs. man-made) nor to differences in microhabitat characteristics associated with concealment.Overall variability of the mitochondrial control region was low in the one northeast Siberian and the three Fennoscandian populations studied. The occurrence of two maternal lineages in all Fennoscandian populations points to mixing of two previously isolated populations. The overall microsatellite genetic structuring (6 loci) in Fennoscandia was low. The pairwise comparison revealed a low but significant degree of differentiation between the Bothnian Bay and the two other Fennoscandian populations. However, no clear indication of genetic effects of small population size in the Bothnian Bay was detected.Matrix and Pradel-λ projection models, based on a ten year (1994–2003) capture-recapture data set, predicted a steep future decrease and a high risk of extinction within 50 years. Without immigration the decline would lead to extinction within 20 years. Population growth was the most sensitive to changes in adult survival, the rate of which declined during the study. Factors affecting adult survival most likely operate primarily during the non-breeding season in locations specific to the study population that are virtually unknown. Management efforts in the Bothnian Bay should, in addition to improving hatching success, first of all guarantee availability of wide, low-sward coastal breeding habitats for potential immigrants and recruits.Academic Dissertation to be presented with the assent of the Faculty of Science, University of Oulu, for public discussion in Kuusamonsali (Auditorium YB210), Linnanmaa, on September 16th, 2006, at 12 noonAbstract
Globally, populations of several wader species are in decline. However, for most populations, information on abundance, its changes and the causes of declines is insufficient for designing successful management strategies to recover threatened populations. In this thesis I studied the status and population trends, nesting success, genetic structure and viability of a small, declining and threatened Temminck’s stint population in the Bothnian Bay in the northern Baltic Sea. Historical population data, recent population counts in the early 1990s and in 1999–2002 and the demographic data showed that the decline is continuing, paralleled by declines in nesting success, recruitment and adult survival.
Decline in nesting success was caused by a coincident increase in nest predation. Depredation was the main cause of nest losses. The common gull (Larus canus) and the ruddy turnstone (Arenaria interpres) were found to be the most important nest predators. I tested if an increase in nest concealment and consequent decrease in visibility lowers the efficiency of the early-departure antipredator behaviour of the species. An expected positive correlation emerged between visibility and flushing distance in the presence of alarm-giving birds, but not without them. This indicates that Temminck’s stint exploits signals from other birds as early warning of an approaching predator. More nests were lost to predation on narrow than on wide shores. The nest predation rate was not related to habitat (natural vs. man-made) nor to differences in microhabitat characteristics associated with concealment.
Overall variability of the mitochondrial control region was low in the one northeast Siberian and the three Fennoscandian populations studied. The occurrence of two maternal lineages in all Fennoscandian populations points to mixing of two previously isolated populations. The overall microsatellite genetic structuring (6 loci) in Fennoscandia was low. The pairwise comparison revealed a low but significant degree of differentiation between the Bothnian Bay and the two other Fennoscandian populations. However, no clear indication of genetic effects of small population size in the Bothnian Bay was detected.
Matrix and Pradel-λ projection models, based on a ten year (1994–2003) capture-recapture data set, predicted a steep future decrease and a high risk of extinction within 50 years. Without immigration the decline would lead to extinction within 20 years. Population growth was the most sensitive to changes in adult survival, the rate of which declined during the study. Factors affecting adult survival most likely operate primarily during the non-breeding season in locations specific to the study population that are virtually unknown. Management efforts in the Bothnian Bay should, in addition to improving hatching success, first of all guarantee availability of wide, low-sward coastal breeding habitats for potential immigrants and recruits
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
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
Factors affecting the availability of thick epiphyte mats and other potential nest platforms for Marbled Murrelets in British Columbia
No full textNest platforms (mossy pads, limbs, and deformities >15 cm in diameter) are key requirements in the forest nesting habitat of the threatened Marbled Murrelet (Brachyramphus marmoratus (J.F. Gmelin, 1789)). Little is known about factors that affect the availability of platforms or the growth of canopy epiphytes that provide platforms. We examined variables affecting these parameters in coastal trees in British Columbia using data from 29 763 trees at 1412 sites in 170 watersheds. Tree diameter (diameter at breast height (DBH)) was the most important predictor of platform availability in the pooled data and within each of six regions. In most regions, platforms become available at DBH > 60 cm, but on East Vancouver Island, DBH needs to be >96 cm and possibly on the Central Coast >82 cm. Other regional predictors of platforms included tree height, tree species, and to a lesser extent elevation, slope, and latitude. Most (72%) trees providing platforms had epiphytes (mainly moss) covering one third or more of branch surfaces and 81% had intermediate or thick epiphyte mats. Mistletoe deformities provided <7% of platforms. Our model predictions help to define and manage suitable habitat for nesting Marbled Murrelets and also contribute to understanding forest canopy ecosystems. [ABSTRACT FROM AUTHOR]Peer reviewedfinal article publishe
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