66,639 research outputs found
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
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
[Letter from Ulmer S. Bird to T. N. Carswell - Feburary 7, 1941]
No full textA letter written to Mr. T. N. Carswell, City, from Ulmer S. Bird, Abilene, Texas, dated February 7, 1941. Carswell discusses the meeting held at the First Baptist Church in Snyder advising of the election of officers, , Secretary Treasurer, to form a county organization as part of the 24th Senatorial District
New insights on accretion in supergiant fast X-ray transients from XMM-Newton and INTEGRAL observations of IGR J17544-2619
No full textXMM–Newton observations of the supergiant fast X-ray transient IGR J17544?2619 are reported and placed in the context of an analysis of archival INTEGRAL/IBIS data that provide a refined estimate of the orbital period at 4.9272?±?0.0004?d. A complete outburst history across the INTEGRAL mission is reported. Although the new XMM–Newton observations (each lasting ?15 ks) targeted the peak flux in the phase-folded hard X-ray light curve of IGR J17544?2619, no bright outbursts were observed, the source spending the majority of the exposure at intermediate luminosities of the order of several 1033?erg?s?1 (0.5–10 keV) and displaying only low level flickering activity. For the final portion of the exposure, the luminosity of IGR J17544?2619 dropped to ?4?×?1032?erg?s?1 (0.5–10 keV), comparable with the lowest luminosities ever detected from this source, despite the observations being taken near to periastron. We consider the possible orbital geometry of IGR J17544?2619 and the implications for the nature of the mass transfer and accretion mechanisms for both IGR J17544?2619 and the supergiant fast X-ray transients (SFXTs) population. We conclude that accretion under the ‘quasi-spherical accretion’ model provides a good description of the behaviour of IGR J17544?2619 and suggests an additional mechanism for generating outbursts based upon the mass accumulation rate in the hot shell (atmosphere) that forms around the neutron star under the quasi-spherical formulation. Hence, we hope to aid in explaining the varied outburst behaviours observed across the SFXT population with a consistent underlying physical model
The design and construction of a flying bird robot
No full textThe purpose of this project is to investigate the issues surrounding the design and construction of a flying bird robot. The ideal would be to re-create a model of a bird that looks like bird, functions like a bird with regard to the biomechanical issues involved in flight and uses control systems that emulate the ones used by the bird to control the flight path
Width-modulated Microstrip-line based Mantle Cloaks for Thin Single- and Multiple Cylinders
No full textA thin mantle cloak is described for electromagnetic footprint reduction for arrays of thin cylinders. The cloaking is obtained by covering the conformal geometry with a metasurface having as a unit cell that is a width modulated microstrip line. Enfoldings at different angles have been considered and numerically studied both for single and multiple cylinders. Frequency scalability and polarization sensitivity of the geometry has also been considered. Experimental results obtained at K-band are in good agreement with numerical data and demonstrate the applicability of the proposed approach for wide-band ( 16%) cloaking applications. The performance of the proposed solution has been compared with available dat
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
A computer vision approach to classification of birds in flight from video sequences
No full textBird populations are an important bio-indicator; so collecting reliable data is useful for ecologists helping conserve and manage fragile ecosystems. However, existing manual monitoring methods are labour-intensive, time-consuming, and error-prone. The aim of our work is to develop a reliable system, capable of automatically classifying individual bird species in flight from videos. This is challenging, but appropriate for use in the field, since there is often a requirement to identify in flight, rather than when stationary. We present our work in progress, which uses combined appearance and motion features to classify and present experimental results across seven species using Normal Bayes classifier with majority voting and achieving a classification rate of 86%
Status assessment of the Critically Endangered Azores Bullfinch Pyrrhula murina
No full text'This work was part of the Azores Bullfinch monitoring programme included in the project LIFE NAT/P/000013 “Recovery of Azores Bullfinch’s habitat in the Special Protection Area of Pico da Vara / Ribeira do Guilherme”'The Azores Bullfinch is endemic to the island of São Miguel (Azores, Portugal). Its status was uplisted to Critically Endangered in 2005 on the basis of an extremely small and declining population that was considered to be restricted to a very small mountain range (43 km2), in a single location, within which the spread of invasive plants constituted a threat to habitat quality. Nevertheless, information was mostly inferred, or the product of, non-systematic studies. In order to carry out a complete assessment of the conservation status we analysed: (i) population trend, calculated from annual monitoring 1991–2008, (ii) population size, and (iii) range size, obtaining estimates in a single morning study in 2008 involving the simultaneous participation of 48 observers. Contrary to previous inferences, the population is no longer decreasing, although quality of laurel forest habitat continues to decline due to the persistent threat of invasive species. Population size (mean ± SE) was estimated at 1,064 ± 304 individuals using distance sampling methods, although the estimate was very sensitive to the survey method used. Range size estimates (extent of occurrence and area of occupancy) were 144 km2 and 83 km2 respectively. Given the present information, we propose the downlisting of Azores Bullfinch to Endangered on the IUCN Red List.Peer reviewe
Control of Surface Reflection Phase by Multiple Embedded Width-Modulated Microstrip Resonators
No full textThe scattering characteristic of normally incident electromagnetic waves from a multiple stacked width modulated microstrip High Impedance Surface (HIS) is investigated. The unit cell is formed by stacking together three, width-modulated microstrip line based unit cells. Parameter values in terms of modulation width in individual cells are changed to characterize the phase reflective device exhibiting advanced controlling features of the observable in a specific wide frequency band. The reflections from stacked structures formed using different modulated but similar unit cells are compared with the reflection from a truly periodic structure consisting of identical unit cells. The effect of the modulation on different layers is discussed. The proposed solution enables efficient control of the reflection phase and hence suggests the configuration for reflectarrays and/or holographic surfaces
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