City Hotspots Research Articles

How would size, age, human disturbance, and vegetation structure affect bird communities of urban parks in different seasons?

Parks are diversity hotspots in cities, and are generalized isolated “islands” in urban landscapes. However, there is a paucity of information on the avian community structure of urban parks in big cities in Southeast Asia, including Hong Kong which has more than 7 million people. This study therefore aimed to assess the influences of park attributes, human disturbance, and vegetation structure on species richness, diversity, total density, and species groups of breeding and wintering bird communities in Hong Kong. Bird communities of 30 parks were censused four times each season in 2010–2011 using point counting. Species richness and diversity were affected by park size in both seasons, and larger parks supported more species and higher diversity. In addition, species richness of wintering season was negatively affected by visitor rate. Total bird density increased with visitor rate, but only in the breeding season. Noise did not have significant impacts on species richness, diversity, and total density. Regarding the responses of species groups, number of resident species increased with park size in both seasons. Migrants, insectivores, and insectivore–frugivores were positively affected by park size, but negatively by visitor rate in the wintering season. However, omnivores in the breeding season increased with both park size and visitor rate. Granivores was the only feeding guild which was positively affected by noise and negatively by foliage height diversity in the wintering season. In conclusion, park size and visitor rate affected bird community structure, and different species groups had different responses to habitat factors in the two seasons.

Soft-Handoff in WLAN Realized by Dual Link

WLAN has been widely deployed in many aspects such as city hotspots and video surveillance system. When the mobile station roams in WLAN, it will switch among different access points (AP). This handoff is hard-handoff which is “break-before-make” . Therefore the latency may result in serious problems in some real-time applications because of losing important data. This paper proposes an efficient dual-soft-handoff (DSH) scheme in WLAN based on the analysis of wireless signal channel allocation. In DSH, STA maintains two active data links to forward AP and backward AP respectively, and they don’t switch at one time. It achieves continuous data transmission during fast motion. Simulation analysis and test results indicate that it can provide seamless handoff and efficient data transfer in WLAN.

Spatial similarity of urban bird communities: a multiscale approach

AbstractAim Human land use, especially urbanization, might homogenize the world's biota. The objective of this study is to find out if urbanization homogenizes wintering bird communities, and if habitat type affects the spatial variation of urban bird communities across spatial scales.Location We compared the quantitative similarity of winter bird communities between town centres, apartment block areas and single‐family house areas across regional and local scales in five towns in northern Finland.Methods The wintering birds were surveyed using a single‐visit study plot (30 ha) method in January and February 2001. The validity of single‐visit and single‐year data was confirmed by using data from several‐visit surveys and multi‐year data set. The level of urbanization was measured according to the number of inhabitants and general structure of the habitat.Results Temporal variability in species richness and total number of individuals was low, both between winters and within winter. Bird community similarity between different habitat types within a single town was about the same as that in similar habitats in different towns. At the regional scale, bird community similarity between town centres (30%) was lower than between areas of apartment blocks (54%) or between areas of single‐family houses (54%). We detected a threshold point between towns of 35,000 and 105,000 inhabitants and between town sizes of 5.0–8.5 km in diameter where human impact causes marked changes in bird community structure. At the local scale, bird community similarity level between apartment block areas (49%) and single‐family house areas (62%) were about the same. Passer domesticus, Parus major and Pica pica dominated the bird communities in residential areas. Different habitat factors affected bird species abundances on the local and regional scales.Conclusions Urbanization cannot be seen as a process that monotonically increases the similarity of bird communities. Our results indicate that the similarity between urban bird communities is dependent on the size of the town, location of the study site within the town and especially the local habitat structure. Because different habitat factors affected bird species abundances, it is difficult to extrapolate bird–habitat relationships derived from one scale to other scales. In wintertime, single‐family house areas are important biodiversity hotspots in cities. Therefore, it is especially important to understand the factors affecting the occurrence of birds in the single‐family house area in order to maintain or even increase diversity on winter birds in other urban habitats.

A habitat island approach to conserving birds in urban landscapes: case studies from southern and northern Europe

Wildlife conservation in urban habitats is increasingly important due to current urbanization trends. We review the different approaches to studying birds in urban landscapes, and point out the impor- tance of the habitat island ecological theory as a research framework for the management and conservation of urban birds. Based on two comprehensive research projects conducted at urban parks in Spain (Ma- drid) and Finland (Oulu and Rovaniemi), several different issues related to bird conservation in cities are discussed, main findings of these projects are presented, and future research needs are suggested. Urban parks are important biodiversity hotspots in cities. Fragmentation conditions have the same deleterious effects to urban birds as in other fragmented landscapes. Park size accounts for species accumulation in urban parks; this pattern being highly nested. Urban parks of 10-35 ha would contain most of the species recorded in cities, but other indicators related to the probabilities of persistence of the target species should be obtained. Wooded streets can increase urban landscape connectivity by providing alternative habitat for feeding and nesting during the breeding season. Because increasing the size of parks is difficult in cities, enhancement of habitat diversity and resource availability for birds within parks (e.g. nest boxes, winter feeding tables, etc.) appears to be a straightforward way of increasing urban bird diversity. However, human disturbance (pedestrians) should be controlled since it can negatively influence many urban birds. We present a conceptual model for urban bird conservation, which includes three aspects (management, environmental education and research) and new alternatives to promote the involvement of different sectors of the society.

NASA helps reduce city hot spots

When researchers from NASA's Marshall Space Flight Center in Huntsville, Ala., recently flew a thermal camera, mounted on a NASA aircraft, over Baton Rouge, La., Sacramento, Calif., and Salt Lake City, Utah, they took each city's temperature and produced an image that pinpoints the cities' “hot spots.”Now, the researchers are using the images to study what types of surfaces in cities contribute to bubble‐like accumulations of hot air, called urban heat islands. The bubbles of hot air develop over cities as naturally vegetated surfaces are replaced with asphalt, concrete, rooftops, and other man‐made materials.