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1.
The Lesser Whitethroat is a very common passerine species with two of the main populations breeding in Europe and in southwest Asia, both wintering in East Africa. These populations must therefore cross the Sahara-Arabian desert belt twice each year. Ring recoveries from northwestern Europe indicate the importance of the eastern Mediterranean flyway between breeding and wintering grounds for this species funneling through Israel. The aim of the study was to describe the staging patterns and phenology of migratory Lesser Whitethroat at the Eilat stopover site located on the threshold of the Sahara-Arabian desert. The number of individuals ringed in spring was on average as much as 25.2 times higher than in autumn passage. We did not find any significant differences in age ratios between passage seasons; however in both seasons adults were recorded earlier than juveniles. Furthermore, the body condition was better during autumn than spring. An analysis of Lesser Whitethroats recaptured during spring passage showed that Eilat is a suitable stopover site for both age classes, which displayed similar staging pattern. Recaptured birds were in better body condition than at first capture, and the improvement of body condition was positively connected with the length of stay at the stopover site. 相似文献
2.
Potential Impacts of Proposed Chenglingji Hydraulic Project on Wetlands in Dongting Lake 总被引：1，自引：0，他引：1
Water level fluctuation of is an important ecological character of lakes in monsoon climate zone.It is the key driver to seasonal change of the wetlands and associated habitats,which provide vital inhabiting conditions for different species in summer and winter,or,wet season and dry season.Due the hydrologic regime changes in the recent years after the operation of Three Gorges Dam,in 2012,the government of Hunan province proposed Chenglingji Hydraulic Project,aiming at water level control in dry season at Chenglingji,where the outlet of Dongting Lake located.Through different operations on water retreat process,five scenarios on the water level control from 21 m to 24 m were set in the plan.The potential ecological impacts of the project are under enormous public concern.To analyze potential impacts from different scenarios of water level control on the wetlands,this paper studied the topography of Dongting Lake bed and wetlands in dry season,by using Digital Elevation Model(DEM)and 15 images from HJ satellite and 1 image from Landsat TM.The wetlands at water levels of 19 m to 27 m were analyzed.The study revealed that there were 4 terrain steps on Dongting Lake bed from the West Dongting Lake to East Dongting Lake.Water level control at Chenglingji would increase area of open water in East Dongting Lake and Hengling Lake areas,while its effect on South Dongting Lake and West Dongting Lake areas due to higher terrain was weaker.Particularly,the area percentages of South Dongting Lake area did not change with water level fluctuation,due to its 2 elevation steps.The area percentages of various types of the wetlands in Dongting Lake area during the processes of water level rising and retreating were quite different,even in the relatively close water level interval.The retreating area of open water in autumn was larger than that during the spring flooding.The 23 m was the key water level,a turning point of the area change of the wetlands in Dongting Lake area.Areas of open water,mudflat,meadows and their percentages changed significantly at water levels above 23 meters,with increasing of open water area and shrinking of meadow area,their areas would decrease 30 000 ha.As the key habitats for wintering geese,the area of meadows was from near 70 000 ha to 10 000 ha.Among 5 scenarios,the impact of the scenario at 21 m elevation on wetlands was the weakest.However,water level dropping was still postponed than that of natural hydrological process in the scenarios.It resulted in longer inundation of large area of lakebed at elevation of 22-23 m,increasing habitats for aquatic biodiversity but reducing area of the meadows,where is the key habitat for wintering geese.All the other water level control scenarios would cause large area of inundation of lakebed in dry season and dramatic change of wetlands.To maintain the natural wetlands in Dongting Lake area,the Chenglingji Hydraulic Project should be considered in a more cautious way and further researches were needed on the response of aquatic biodiversity and wintering water birds. 相似文献
3.
South-western Greenland constitutes an internationally important wintering area for many seabird species. Several species of management concern have a predominantly near-coastal distribution, though available information about seabird numbers is mostly confined to offshore waters. Here we report on extensive aerial surveys conducted in March 1999, covering the coastal waters (up to 15-20 km from the mainland coast) and fjords of south-west Greenland. The most widespread and numerous species were estimated as 463 000 common eiders ( Somateria mollissima ), 153000 king eiders ( S. spectabilis ), 125000 thick-billed murres ( Uria lomvia ), 94 000 long-tailed ducks ( Clangula hyemails ), and 12 000 black guillemots ( Cepphus grylle ). A total of 19 bird species were recorded. The estimates for common eider and long-tailed duck approximately represent the entire winter population in south-western Greenland while estimates for the other species represent only an unknown proportion since their distribution continues further offshore. Waters around Nuuk and within the Julianehåbsbugten (Julianehåb Bay) area were identified as areas of high seabird density. A large proportion of the common eider population was aggregated in the fjord systems (22%), calling attention to the importance of fjords for this species. In contrast, pelagic seabird species appear to be absent from the fjords. The large winter population of common eider reveals the importance of south-western Greenland as a key wintering area for the eastern Canadian breeding population. The western Greenland breeding population is the only other contributor, probably amounting to no more than 15 000 pairs. 相似文献
4.
对南极长城站和中山站两地的贼鸥种群进行包括营巢行为、觅食习性、种群变化、繁殖生态 ,以及贼鸥栖息地的地理和生态环境等的比较研究 ,结果表明两地贼鸥种群存在明显的生态学差异。这种差异不仅反映了贼鸥的生态习性与栖息地自然环境和生态结构的密切相关性 ,更体现了该种海鸟对南极不同生存环境极强的适应能力。人类活动以及贼鸥对人类废弃食物的依赖 ,在一定程度上改变动物食物结构 ,并对贼鸥生态习性乃至种群数量变化均产生一定影响。两地贼鸥种群通过改变觅食对策和调整产卵、孵化时间和延长育雏期等 ,达到对不同地理纬度和气候条件的适应 ,确保物种的延续 相似文献
5.
Impact of the Arctic Fox Alopex lagopus on nesting success of geese in southeast Svalbard, 1989 总被引：1，自引：0，他引：1
Goose populations, with special emphasis on Light-bellied Brent Geese Branta bernicla hrota , were censured in Tusenøyane and Tjuvfjorden, southeast Svalbard, July-August 1989. A total of 425 non-breeding Brent Geese, 210 Barnacle Geese Branta leucopsis and 421 Pink-footed Geese Anser bra-chyrhynchus and 11, 2 and 3 families of the three species, respectively, were counted. Brent Geese attempted to nest on 6 of the 20 islands surveyed, and were successful on four. Barnacle Geese attempted to nest on three islands and were successful on two. Many islands known to be traditional nesting sites were entirely void of geese. Pink-footed Geese were only seen in Tjuvfjorden. The breeding failure on the islands was linked to the presence of the Arctic Fox Alopex lagopus which probably caused the geese to completely give up the attempt to nest. On one island the fox had apparently arrived after nest initiation and ravaged 45 Brent Goose and Barnacle Goose nests. It is likely that the foxes stranded on the islands during ice break-up. As a consequence of the presence of foxes on most of Tusenøyane, more than half of the potential breeding segment of the Svalbard Brent Goose population failed to nest in the summer of 1989. 相似文献
6.
Vegetation exploitation by barnacle geese Branta leucopsis during incubation on Svalbard 总被引：1，自引：0，他引：1
The paper is a study of vegetation exploitation and the effect of food availability on the diet and behaviour in barnacle geese breeding at Storholmen, Svalbard. Detailed vegetation mapping was used to estimate the availability of food to individual pairs of geese. Diet composition was assessed through analysis of plant fragments in droppings. The behaviour of geese in relation to snowmelt patterns was recorded. Most vegetation types were exploited by the geese either for feeding or as nest substrate. Nest density was highest and territories were smallest on early, snow-free ridges, although late breeding individuals also nested in moss tundra vegetation. Most geese pairs exploited a mosaic of vegetation types in their territories, which extended the feeding period when plants were nutritionally most profitable to the geese. Territory size increased with decreasing density of the highest preferred food plants. Female geese preferred plants with high nutrient quality, and the diet during incubation consisted of 41% flowers of forbs, 19% grasses, 6% leaves and buds of forbs, and 34% mosses. When the availability of grasses was <5%, geese switched to a diet dominated by the abundant, but nutrient-poor, mosses. The nutrient-poor diet resulted in more time off the nest and less time being alert or searching for food during feeding bouts. Because nests are exposed to predators when females feed or search for food, a low availability of nutrient-rich food within the territory can affect hatching success. 相似文献
7.
Habitat management is essential for the conservation of wildlife, especially cranes. Here, we collected occurrence data at wintering grounds for four cranes (Leucogeranus leucogeranus, Grus monacha, Antigone vipio and G. grus) and analyzed associated environmental variables to model and project overall potential wintering habitat using Maxent. ENMTools was used to calculate the degree of niche overlap among cranes. Results showed that lakes in the middle and lower reaches of the Yangtze River are main habitats for the four focal species. Inland water and coastal wetlands in Jiangsu are also potential wintering areas. G. grus spreads over central and eastern China. The four cranes show tight niche overlap in the middle and lower reaches of the Yangtze River. Poyang Lake is one of the most important habitat sites for all four cranes, according to modeling and niche overlap results. Poyang Lake is cut into a dozen nature reserves, but a bigger nature reserve or system would be more effective for cranes. The conservation of these four crane species will be improved on the basis of this study. 相似文献
8.
中国西部及邻区现代年降水时空分布初步研究 总被引：1，自引：0，他引：1
传统上认为中国东部、西南以及青藏高原南部的降水主要受亚洲夏季风的控制,以夏季降水为主;而青藏高原北部以及新疆受西风带的影响,以冬、春季降水为主。最近一些地质记录和数值模拟结果显示,在万年时间尺度上新疆降水在地质历史时期的间冰期增加,和亚洲季风区类似。用TRMM 3B43降雨数据和气象台站观测降水数据,研究了中国西部及邻区现代年降水的时空分布。研究结果显示现代中国西部地区以夏季降水为主,中国边境线以西的中亚干旱区(介于25°45°N,58°45°N,58°70°E之间)以冬、春季降水为主。中国新疆的降水模式不同于西风带影响区,但其降水也不全是亚洲夏季风带来的。 相似文献
9.
A total of 138 walruses ( Odobenus rosmarus rosmarus ), including 21 cow/calf pairs, were observed during a ship-board survey in the southeastern Barents and Pechora seas 5-17 February 1993. The observations confirm these areas as wintering and nursery grounds for the species. 相似文献
10.
A. Si BachirF. Ferrah C. BarbraudR. Céréghino F. Santoul 《Journal of Arid Environments》2011,75(11):1232-1236
This study identifies new information on the recent distribution of an invasive bird species, the Cattle Egret Ardea ibis, in Algeria. Breeding and wintering distributions as well as breeding numbers were obtained from large-scale surveys in 1999 and 2007, and from historical data. Between 1999 and 2007, the total number of colonies found increased from 51 to 87, and most were located in the northern part of the country. The breeding distribution area, confined to the coastal areas in the 1970s, has shifted further south, and reached the northern part of the Sahara since the 2000s. Most colonies were established during the period 1980-1995. The oldest colonies were generally larger than the recent ones. The number of colonies increased by 83% between 1999 and 2007 in the 12 administrative units (wilayas) surveyed. The number of breeding pairs increased from 7765 in 1999 to 28544 in 2007, corresponding to an annual population growth rate of 17.7%. The changes in distribution and population dynamics since the 1970s and the potential factors affecting these changes are discussed. 相似文献
11.
Ecological differences of south polar skua populations from Fildes Peninsula of King George Island and eastern Larsemann Hills, Antarctica 
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下载免费PDF全文 A study has been done on the comparison of nesting and feeding behavior, population variances as well as breeding success between two populations of south polar skua (Catharacta maccormicki) from near Great Wall station on Fildes Peninsula and near Zhongshan station in Eastern Larsemann Hills, Antarctica. There are evident differences in their population ecology. The foraging habit is much related to regional ecosystem and food resources near their territorial area. Dependence on human food waste influences skua's diet,which considerably affects their behavior even population variation in both areas. The skuas in Zhongshan Station,could shorten and/or regulate the timing for their egg laying and hatching, and take precedence of one chick brooding, for keeping their breeding success, and subsequent species continuation. 相似文献
12.
劳动力成本上升与中国制造业空间转移 总被引：3，自引：2，他引：1
采用中国规模以上工业企业数据,建立面板数据回归模型,研究了劳动力成本上升对制造业空间转移的影响,主要有以下研究结论：① 劳动力成本提升已成为推动中国制造业空间转移的重要影响因素。2004年以前发达地区相对较高的工资水平并未影响到产业集聚,但是2004年以后较高的工资水平开始推动制造业企业向工资水平较低的地区迁移,但出口型企业与满足国内市场需求的制造业企业体现出了不同的转移路线。② 2004年以前中国制造业总体上不断向长三角、珠三角以及山东半岛等地区集中,2004年以后制造业开始向沿海相对较为落后的江苏北部、山东中西部以及中国中西部地区迁移,满足国内市场需求的制造业企业是向中西部地区迁移的主体,出口型企业由长三角和珠三角向东部地区的山东半岛和辽东半岛等交通条件较好的地区迁移。③ 东部地区产业升级缓慢。尽管产业向外转移,但东部沿海地区的产业尤其是满足国内市场需求的制造业企业仍然以劳动力驱动为主,资本驱动的特征并不明显。但出口型企业的发展率先表现出了资本驱动的特征。 相似文献
13.
Late in the summers of 1997 and 1998 surveys of common eider ( Somateria mollissima ) colonies were conducted throughout Avanersuaq Municipality in north-west Greenland. Although old information from eider colonies was available, these surveys provided the first almost all colonies in the district, thereby improving the baseline data for assessing future population changes. The surveys were based on nest counts, and all but two colonies in the district were counted, In total, 3800 nest were counted and an educated guess for the total population in Avanersuaq Municipality, including the two inaccessible colonies, would be around 5000 pairs. Average clutch size was 3.74 similar to or higher than in other areas of Greenland and high Artic Canada suggesting favourable conditions for eiders in the survey area. Comparison with older data suggests that the breeding population in Avanersuaq is stable. This observation contrasts with the declines ocserved in other parts of Greenland. Further studies into possible population specific mirigation routs and wintering areas as well as the direct and indirect effects of the intensive winter hunting in south-west Greenland are warranted. 相似文献
14.
山东寿光滨海国家湿地公园湿地保护与恢复措施和工程探析 总被引：2，自引：0，他引：2
山东寿光滨海国家湿地公园中,湿地类型多样,动植物资源丰富,珍稀濒危物种和特有种多,具有很高的保护价值.该湿地公园中的湿地为典型的人工湿地,在经历了人类活动的高强度干扰后,人工湿地明显退化,亟需通过生态技术或生态工程对退化的湿地进行恢复和保护.通过分析区域现有湿地水文、水质条件以及湿地类型、资源现状和目标保护物种分布,综合考虑水源地,以湿地资源有效保护为根本出发点,运用生态保护规划的理论和方法,通过水系贯通、湿地功能恢复、水质和动植物生境改善等一系列生态重点工程和措施,优化该湿地公园的湿地生态环境,使该公园的湿地充分发挥它的多种功能,为该公园的湿地保护与恢复规划提供科学依据. 相似文献
15.
根据云南省内若干山区气象资料,研究云南山区日照时效的垂直分布规律,得出一些有意义的结论:日照时数垂直分布有抛物线型、线性型、缓变型等;日照时数年内变化有冬大夏小型、春大夏小型、夏大冬小型3种;山区日照时数坡向差异明显,各山区不尽相同。 相似文献
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17.
The Hudson Bay common eider ( Somateria molissima sedentaria ) is a unique subspecies of eider that remains within the confines of Hudson Bay throughout the year. We compared clutch, egg and body size variation among populations of common eiders breeding in eastern and western Hudson Bay. Clutch size did not differ substantially among these populations. All eiders in Hudson Bay laid larger clutches than other subspecies in eastern North America. As Hudson Bay common eiders do not undergo extensive migrations, they may have more energy reserves available to them for egg production. Eiders nesting in eastern Hudson Bay laid larger eggs than eiders nesting in western Hudson Bay. Further, eiders in eastern Hudson Bay tended to be structurally larger, but had smaller bill processes. These differences may have a genetic basis. Smaller egg size and body size may arise in western Hudson Bay from mixing with the smaller borealis subspecies nesting to the north. Further work to resolve genetic affinities, determine levels of male and female dispersal, and examine variation in reproductive ecology are needed to resolve the sources of these differences. 相似文献
18.
We examined the stability of fast ice areas in western and northern Spitsbergen, the area north of Nordaustlandet, the bays and sounds of Hinlopen Stretet and the large area in the northern part of Storfjorden. NOAA satellite imagery from 1974 and 1988 and NOAA (AVHRR) imagery from 1980-87 were used to determine the dates of freeze-up and break-up. The number of days of fast ice present before the nominal birth date of ringed seal pups were computed for all major bays and fjords. Ice thickness was then computed from these data. Known prime breeding habitat in Svalbard is found in areas near glacier fronts in protected fjords and bays, where densities of birth lairs are 5.46 km−2 , corresponding to a ringed seal female density of 2.6 km−2 . Most of the ringed seal breeding habitat in Svalbard, however, consists of flat fjord ice where snow accumulation is rarely deep enough to permit birth lair construction. In these areas pups are often born in the open. Based on breathing hole densities, the density of adult females in the flat ice areas in the breeding period was estimated to 0.98 km−2 . A preliminary estimate is that approximately 19,500 pups could be born annually in the fast ice of Svalbard. Annual recruitment could be quite variable given the unpredictable nature of the fast ice areas and the high predation mortality on newborn pups. Discrepancies between our calculated ringed seal production and numbers of seals required to feed the large polar bear population in the area signal cause for management concern. 相似文献
19.
对东南极中山站附近麦氏贼鸥巢区和无巢贼鸥群栖地的贼鸥回吐渣团及其他食物残物进行收集、分析和鉴定 ,结果表明 ,本区麦氏贼鸥主要捕食雪 ,其残物在食物项中的平均出现率为 6 7～ 80 %;同时贼鸥从本区几个考察站觅取人类遗弃的垃圾食物作为其重要的食物补充 ,垃圾食物的平均出现率为 6 .8～ 1 1 .6 %。不同巢区贼鸥对雪 的捕杀量和垃圾的需求差异较大 ,其主要与营巢地域的雪 分布密度以及摄食区的占有与否有关。 相似文献
20.
《Norsk geografisk tidsskrift. Norwegian journal of geography》2012,66(1):20-30
Gjellan, A. 1975. Protection of bird wildlife. Norsk geogr. Tidsskr. 29, 21–38. Plans for establishing bird wildlife nature reserves and areas where bird wildlife can be protected are discussed. Areas already established for this purpose are mentioned, as are other important areas worthy of protection. An attempt is made to evaluate the criteria for the selection of such important areas in the future. A classification is made of the areas in question, such as wetlands and other biotope types in forest and mountain localities. The main criterion is that the area should satisfy at least one important life function, such as breeding, foraging and resting (primarily of migrating birds), moulting, and wintering. The man-made threat towards the maintenance of these natural areas for the preservation of bird wildlife must be controlled, and the resources available for conservation must be well argued by public and private nature conservation organizations and institutions. 相似文献