71,809 research outputs found
Estimating bird abundance : making methods work
No full textIn many bird monitoring Surveys, no attempt is made to estimate bird densities or abundance. instead, counts of one form or another are made, and these are assumed to correlate with bird density. Unless complete Counts Oil Sample plots are feasible, this approach can easily lead to false conclusions, because detectability of birds varies by species, habitat, observer and many other factors. Trends in time of counts often reflect trends in detectability, rather than trends in abundance. Conclusions are further compromised when surveys are conducted at unrepresentative sites. We consider how to avoid these problems. We give a brief description of distance sampling methods, which allow detectability to be estimated. We consider strategies to ease their implementation, to enhance their reliability, to adapt the methods for difficult species, and to deal with circumstances in which representative sampling is problematic. We also consider some of the common problems encountered, and suggest solutions.Peer reviewe
Bird species richness and diversity at montane Important Bird Area (IBA) sites in south-eastern Nigeria
No full textThe mountains of south-eastern Nigeria are a western extension of the Cameroon mountain range, which is classified as an endemic bird area (EBA). Unlike its eastern extension in Cameroon, most of the ornithological surveys in the western extension of the Cameroon highlands in Nigeria have produced only limited checklists and inventories. There is a clear need for quantitative baseline data so that conservation problems can be identified. Twenty line transects covering a total transect length of 28.8 km were used to survey five sites (Afi Mountain Wildlife Sanctuary, Oban and Okwangwo Division of Cross River National Park, Sankwala Mountains and Mbe Mountains) in the westernmost extension of the Cameroon Mountains EBA in south western Nigeria. Vegetation measurements were taken to control for the potential confounding effect of variation in vegetation density and structure on detectability of birds between sites. The 193 bird species recorded in Afi, 158 in Sankwala, 124 in Oban, 100 in Mbe and 73 in Okwangwo Division included most of the Cameroon highlands restricted range species. The results show that the mountains of south-eastern Nigeria are important parts of the Cameroon EBA, particularly the Afi Mountain Wildlife Sanctuary. However these sites are threatened by fire and livestock grazing on the hilltops, shifting agriculture on the hillsides and lowlands, and logging for timber in some parts, as well as wildlife hunting for bush meat.Peer reviewe
Study Design and Testing of Structural Configurations for the bird-strike compliance of aeronautical components
No full textThis work is the result of a collaborative research project between the univer-
sity (Department of Aerospace Engineering at University of Naples "Federico
II") and an industrial partner (Alenia Aeronautica at Pomigliano d'Arco).
The aim of this project was to design, with the help of nite element analy-
sis and the experimental tests, an aircraft wing leading edge structure with
innovative materials, that satises the optimization of requirements such as
weight and performance. This study was driven by the industrial demand
to improve the design rules necessary to the evaluation of the structural
response of a leading edge when subjected to bird-strike.
The rst step was the material characterization: an extensive series of
materials was tested to determine stiness and strength properties on glass-
based ber metal laminate. Static tests were performed to determine the
stress-strain curve, dynamic tests to evaluate material strain rate sensitivity
at medium rate regime and, impact tests to determine the threshold for
impact energy which correspond to visible impact damage.
Afterwards several congurations of an one-bay component of a typical
wing leading edge were built and subjected to the bird-strike tests carried
out at Alenia plant by an air pressure gas gun facility. Various materials,
lay-up distribution and boundary conditions were investigated. The numer-
ical nite element simulations were performed using the commercial explicit
integration code MSc/Dytran. This work describes the basic assumptions of the analyses, i.e. bird properties, composite failure modes, and the way in
which the simulations have been carried out in an industrial environment.
Numerical simulations were able to predict that the bird did not penetrate
the leading edge skin. The nal correlation between numerical and experi-
mental showed that good correlation was achieved.
Finally the tests were useful to design and test a new conguration of
leading edge structure able to satisfy the bird-strike requirement according
to the Federal Aviation Regulation (FAR part 25, section 25.631 "Bird-strike
Damage"). Compliance with this section we studied the conguration of the
C27J aircraft, that presents a cruise velocity of 464km/h (=250kts), so the
impact speed with an 8-pound bird is a potentially serious and damaging
event that must be accounted for the design of
ight critical aircraft com-
ponents. The starting thickness of the n C27J airplane's aluminium alloy
leading edge was 0.8mm with a weight of 12.1kg. Before this work, to satisfy
the airworthiness standards about the bird-strike damages, the thickness of
the aluminium alloy leading edge was increased to 3.2mm with a skin weight
of 36.8kg, this thickening involved a weight increasing of 305% related to
skin thickness of 0.8mm.
After this research work, to certicate the empennage structure after im-
pact with an 8-pound bird according to requirements, a innovative composite
conguration has been studied, which oered an amount weight of 18.2kg
producing a weight conservation of 51% related to leading edge in aluminium
alloy with a thickness of 3.2mm. Furthermore this research project allows to
validate a ribless conguration about the leading edge; this solution aided
the manufacturing reducing the rib's installation onto the leading edge struc-
ture. The leading edge conguration in the ber metal laminate and ribless
has been tested at impact with an 8-pound bird at a speed of 250kts and
the test has been considered highly satised and it has met the quality of
requirements
Memorials : Associative Meanings
No full textThis chapter explores the relationship between memorials and their locations, virtual and physical, with an emphasis on the importance of the latter for analysis. The main focus is on the interplay between the spatial, temporal and associative contexts of war memorials, and how the historian can explore these. Memorials both define and are defined by their locations. Where some memorials are seen to complement and be complemented by their environment, others exist in tension with their surroundings and generate controversy. Inadvertent juxtapositions can have an unintentional impact on how a memorial is read. The dialogue between memorial and location is thus examined in both geographical and discursive contexts, with specific examples drawn from Coventry, London and Staffordshire in the United Kingdom, as well as from Berlin and New York. © 2020 selection and editorial matter, Sarah Barber and Corinna M. Peniston-Bird; individual chapters, the contributors
Cooperation bibliogram of bird flu
No full textThe published literature on Bird Flu, now a pandemic animal disease with a possible potential of evolving into a devastating human disease, was analysed primarily with respect of national and international cooperations and networks of authors and countries. The output of research-relevant papers is now around 150 per year and was less than 100 papers per year before 2003. The field is highly cooperative; nearly 90% of the articles have two or more authors. National extramural cooperation is around 50% since 1998, intramural cooperation shows a decreasing tendency and is now about 20%. Between 20% and 30% of the papers have been published in bi- or multinational cooperation. Observed and expected citation rates of international papers are twice as high as the citation rates of national papers.
47 countries are engaged in Bird Flu research, on top USA, followed by PEOPLES R CHINA, UK and JAPAN. These countries are also centers of country networks, but minor centers exist. An Asian local network with strong ties consisting of countries most affected by Bird Flu can be identified.. No strong direct connections exist between Europe and Asia; thus it seems necessary to intensify international cooperation.
Author network show interesting cluster structures which must be studied in detail
Relationships between hedgerow characteristics and bird communities:: a multivariate approach
No full textFifty 100m hedge transects were selected within 10km of Durham City, North England. The bird community of the hedge transects was censused six times between May and July, and characteristics of the hedge and surrounding landscape were recorded. The data was analysed using multivariate methods to determine the importance of the microstructure of the hedge in relation to aspects of the bird community. Stepwise Multiple Regression selected the scores of the first axis of a Detrended Correspondance Analysis of shrub abundance data (related to the height and width of the hedge) as the best predictor of Bird species richness and density. Individual species were related to different aspects of the hedge microstructure. The use of transformed independent data improved the predictive value of most of these relationships. A Detrended Correspondance Analysis found that major source of variation in the bird species abundances was due to the number of trees in the hedge. Canonical Correspondance Analysis was used to analyse how a community responds to a set of external factors. The CANOCO first axis was related to an increase in the area of nearby woodland in the positive end and an increase in the number of trees in the negative end. The position of the species scores in relation to these environmental gradients was analysed. The habitat preferences of 4 common species of bird was explored using "sector” analysis, whereby the mean density of the species is plotted against the major sources of variation in the environmental variables, different habitat preferences between species are apparent. The importance of trees to the bird community was elucidated using Linear Discriminant Analysis. The analysis was carried out with hedges with no trees and hedges with 3 or more trees as the two a priori groups. Eighty-three percent of the sites were placed in the correct groups, using 14 common bird species as variables. The importance of the microstructure of the hedge to the bird community is discussed
Evaluating the Effects of a Bird Strike Advisory System
No full textBird strikes have operational impacts and cause economic loss to the aviation industry. In the worst case, the damages resulting from bird strikes lead to crashes. The highest risk for bird strikes is in the area below 3000 ft and thus mainly in airport environments. Despite intense efforts from the airports in controlling the local bird populations, the number of bird strikes in these environments is still very high. Usually, Air Traffic Control is neither integrated into the process for reducing bird strikes nor do the controllers receive any precise information about the current bird traffic situation at the airport. For the project described in this paper, we assume a different situation: Air Traffic Control is provided with a tool informing the controller about the current and predicted bird traffic at the airport. Based on this information, the controller can decide to delay departing air traffic in order to avoid potential collisions between birds and the aircraft taking off. When implementing this procedure at an airport, we expect an increase in airport safety and, due to the delaying of traffic, a reduction in runway capacity. We hypothesize, that the Relations between the settings of the alerting systems and the effects on safety and capacity are deterministic. To test this hypothesis, we will perform
fast-time simulations under varying conditions. This paper describes the simulation environment created for this purpose
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