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Populations of the Critically Endangered hawksbill turtle Eretmochelys imbricata in the Seychelles showed significant declines in the past. They have since recovered and nesting numbers are increasing because of increased protection and management intervention. Data on their nesting ecology on Cousine Island were collected and analysed for the breeding seasons from 2004/2005 to 2013/2014 with the aim of improving management methods. The findings indicate that the number of nesting individuals increased during the study period (from x? = 34.3 nesters between 2004 and 2009, to x? = 55.4 nesters between 2010 and 2014); however, the clutch frequency was relatively low compared with other study areas. Night-time nesting increased, most likely because of increased disturbances across the study period. Clutch sizes decreased significantly across the nesting season, and there was a significant drop in hatching success in clutch sizes exceeding 200 eggs. The predation rate and infertility rate each showed an increasing trend over time. Nests incubating in full sun showed the highest mean hatching success rate and had the shortest mean incubation duration. The present study provides insight into the species’ nesting ecology on Cousine Island and will better inform management decisions aimed at increasing hatching success and minimising threats such as beach erosion and predation. 相似文献
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Patterns of waterbird community composition across a natural and restored wetland landscape mosaic,Yellow River Delta,China 总被引:1,自引:0,他引:1
Donglai Li Sihang Chen Lei Guan Huw Lloyd Yueliang Liu Juanzhang Lv Zhengwang Zhang 《Estuarine, Coastal and Shelf Science》2011
Habitat restoration can help mitigate the extensive loss and degradation of estuarine and coastal wetlands that have consequently eroded the integrity of many migratory flyways and wintering habitat for waterbird populations. Assessing the impact of restoration strategies however relies on empirical data on waterbird community distribution patterns across natural and restored wetland components. We conducted habitat and waterbird surveys across six natural and restored wetland regions in the Yellow River Delta Nature Reserve (YRDNR), eastern China, between 2007 and 2009. We recorded 93 waterbird species, including populations of 21 global conservation importance species. Community composition was stratified into distinctive clusters with compositional structure changing across these natural, modified and restored wetland components. NMDS ordination revealed that waterbird communities in restored wetlands were significantly different from those in natural and modified wetland components. Community distribution patterns were strongly influenced by environmental gradients (most noticeably salinity), water-level regulation, vegetation composition and differences in protected status. We found marked temporal patterns in waterbird community composition, which may be predictable for the different wetland components across the YRDNR landscape. Our study highlights the conservation benefits of restoring smaller wetland components in improving the ecological integrity of the wider wetland landscape mosaic for waterbird populations. A more coherent and intensive landscape management of water-level regulation and restoration of salinity gradients will be fundamental for wetland and waterbird conservation throughout the YRDNR. 相似文献
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吊舱式直升机频率域电磁、磁综合系统(以下简称“吊舱系统”)采用新型的宽带技术,数字化程度较高,系统较为灵活,尤其适合于地形较为复杂地区的矿产和水工环勘查工作。但由于吊舱系统在复杂山区飞行难度大,且没有实际工作经验,因此通过选择3个测区的吊舱系统试生产工作,在测量方法技术,数据处理方法和成果解释方面,以及基础地质研究、矿产勘查、地下煤火勘查方面均取得了显著成果。解决了航空电磁方法探测地下煤火区的电性结构特征问题,以及航空电磁方法直接寻找良导矿体的关键问题,弥补了航磁间接寻找多金属矿的不足,并取得了明显的勘查效果。 相似文献
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《African Journal of Marine Science》2013,35(4):589-592
The main impact of the fishery for Tristan rock lobster Jasus tristani on seabirds at the Tristan archipelago and Gough Island is through night strikes, when petrels collide with a ship after being disorientated by its lights. Tristan fishery observers have kept records of night strikes on the MV Edinburgh since the 2010/2011 fishing season. Over the last three years, 723 seabirds from nine species were recorded coming aboard the fishing vessel, with at least 39 (5.4%) birds dying as a result. Birds killed were broad-billed prions Pachyptila vittata (41%), common diving petrels Pelecanoides urinatrix (23%), and storm petrels (Pelagodroma marina and Fregetta grallaria/tropica 36%). All these species are listed as Least Concern globally, and the numbers killed per year are <0.1% of the island populations. The captain and crew of the Edinburgh are aware of the problem posed by deck lights at night, and attempt to keep external lighting to a minimum. As a result, the numbers of birds coming aboard vessels in this fishery have decreased from an average of 130 birds per night in 1989 to less than two birds per night in 2010–2013. Currently, most incidents occur during exceptional events when circumstances require deck lights to be lit at night. Consideration should be given to banning fishing operations at night, at least on misty nights. 相似文献
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Age of the pterosaur and web-footed bird tracks associated with dinosaur footprints from South Korea 总被引:2,自引:0,他引:2
Cheong-Bin Kim Min Huh Chang-Sik Cheong Martin G. Lockley Ho-Wan Chang 《Island Arc》2003,12(2):125-131
Abstract An absolute age has been determined for the Cretaceous Uhangri Formation in which web-footed bird tracks, pterosaur tracks and dinosaur tracks have been discovered recently. This combined track discovery is a first from Asia. There is one other similar find in the world, however, the Uhangri site is greater in abundance and frequency. Moreover, the size of the pterosaur tracks indicates that the track maker had a wingspan of 10 m or more. Well-preserved tuffaceous rocks in the formation made it possible to measure geological age by Rb–Sr and K–Ar methods. Rb–Sr whole rock ages for the volcanic rocks are: 96.0 ± 2.5 Ma (MSWD = 0.354) for lapilli andesitic tuff, 81.0 ± 2.0 Ma (MSWD = 0.296) for felsic tuff and 77.9 ± 4.1 Ma (MSWD = 4.41) for Hwangsan welded tuff. K–Ar ages are younger, 83.2–68.8 Ma. The layer containing fossil tracks of pterosaurs and web-footed birds are preserved in black shale sandwiched by the lapilli andesitic tuff and felsic tuff, and are thus 96–81 Ma in age. Dinosaur footprints are dated at 96–78 Ma. Thus the pterosaurs, web-footed birds and dinosaurs coexisted in the same environment from Cenomanian to Campanian time. 相似文献
39.
研究表明,内蒙古包头市阿善遗址的鸟类化石总计有5目7科10属10种鸟类,其中赤嘴潜鸭、白枕鹤和骨顶鸡为中国鸟类首次化石记录。阿善遗址鸟类群除3种为鸡形目地栖者外,其余全为涉水鸟类,是中国迄今为止首次发现的以水鸟为主体的史前时期鸟类群。这些鸟类化石对研究遗址的生态环境、气候变化以及鸟类地理分布、迁徙和演化等都有重要意义。 相似文献
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