内蒙古图牧吉冬季大鸨调查初报

大鸨(Otis tarda)属大型草原鸟类,过去曾广泛分布于黑龙江省西部及内蒙古的东部,目前已经处于濒危状态。图牧吉自然保护区是大鸨的主要栖息地,繁殖数量约200多只。1998年开始记录到越冬大鸨个体,2003年冬季,本区越冬数量达到165只(其中保护区内记录到85只)。本文对图牧吉自然保护区大鸨的越冬数量分布进行了调查,并对大鸨越冬行为及食性进行了初步的观察和分析,对大鸨越冬地管理及越冬鸟类的保护提出了建议。     

北京地区黑鹳越冬期的取食行为

2004年12月至2005年3月在北京十渡地区的二渡和涞水县野三坡两地采用目标取样法对越冬期黑鹳(Ciconia nigra)的取食行为进行了观察。每星期观察一次,累计观察246 h。黑鹳觅食处水深5~40 cm左右,以鱼类和螺类为食,其中鱼类占90%以上;平均每小时进食20次左右,黑鹳在两个研究地点取食的食物没有差别(P=0.439>0.05)。黑鹳取食长度小于4 cm的鱼类最多,占取食总次数的65.0%。成体和亚成体对不同大小鱼类的取食比例无差异(小于4 cm的鱼类,P=0.513>0.05;5~8 cm,P=0.979>0.05;≥9 cm,P=0.657>0.05)。在成体与亚成体对不同体型鱼类的搜寻时间中,成体搜寻较小食物的时间短于亚成体(P=0.008<0.05)。对食物的处理时间随着鱼类大小递增而延长,亚成体在处理较小食物上花费的时间相对较长(小于4 cm的鱼P=0.002<0.05;5~8cm的鱼P=0.001<0.05),表明亚成体的取食经验不足。保护越冬期黑鹳的最佳对策是减少对其取食活动和取食地的人为干扰。     

我国丹顶鹤栖息地选择研究进展

丹顶鹤(Grus japonensis)是我国Ⅰ级重点保护野生动物,被世界自然保护联盟列为濒危物种。本研究通过搜集和整理2000至2017年丹顶鹤栖息地选择和生境适宜性相关文献,分析了丹顶鹤在繁殖期、迁徙期、越冬期的栖息地选择,发现丹顶鹤在这三个时期的最偏好生境均为芦苇沼泽或芦苇滩,回避人为干扰较为严重的居民点、道路、盐田等生境。通过梳理丹顶鹤繁殖地、中途停歇地、越冬地的栖息地变化及其原因,发现丹顶鹤栖息地变化是自然因素和人为因素共同驱动的结果,以人为因素为主。本研究希望为科学评价栖息地变化对丹顶鹤野生种群的影响、针对性地开展栖息地保护管理工作、促进丹顶鹤野生种群健康可持续发展提供依据。     

青海湖裸鲤自然产卵场的生境特征及无人机遥测判别——以泉吉河为例

自然产卵场是维持物种延续最关键的栖息地,青海湖裸鲤（Gymnocypris przewalskii）的自然繁殖栖息地状况和生境特征尚缺乏详细的定量研究。以青海湖入湖河流泉吉河为例,在平水期采用现场调查和无人机遥测的方法对青海湖裸鲤的自然产卵场分布及生境状况进行调查,确定其产卵场生境特征参数,建立基于无人机遥测识别产卵场的方法并进行复核验证。结果表明：泉吉河河道形态可分为弯曲型、分汊型和顺直型等三种典型河型,青海湖裸鲤自然产卵场主要分布在弯曲型和分汊型河道中,分汊型河道几乎100%都有产卵场分布,弯曲型河道有70%为产卵场;产卵场河道平均长度（135.13±61.13） m,平均宽度（30.01±17.51） m,平均曲折度1.09±0.07;平均面积（4586.6±4201.61） m²;产卵场常位于缓水浅滩处,平均水深（0.19±0.10） m （范围：0.03-0.44m）,平均流速（0.24±0.20） m/s （范围：0.01-0.81m/s）,河床质为含有沙粒的卵石（粒径：163-256mm）底质。河道形态、沙洲分布、水深特征等特征参数可作为无人机遥测识别产卵场的判断条件,并实现验证成功。研究结果可为开展整个流域的青海湖裸鲤自然产卵场现状评估及保护对策制定提供技术支撑。     

鄱阳湖保护区白琵鹭越冬种群分布

2007年10月至2010年3月3个冬季的调查显示,鄱阳湖国家级自然保护区白琵鹭(Platakakucorodia)种群数量在12月或1月达到峰值,3个越冬期最大种群数量分别为4 757只、10 385只和7 268只.大湖池、沙湖、常湖池是白琵鹭主要的栖息地,每个越冬期在这3个湖泊栖息的白琵鹭种群数量占保护区总数量的...     

The distributions of larval and juvenile fishes in Amazonian rivers of different nutrient status

1. Previous work has indicated, at least in two river systems, that some Characiformes species migrate from nutrient‐poor rivers to spawn in nutrient‐rich rivers. In the present work, larval and juvenile fish were surveyed to index spawning activity in order to determine whether this spawning pattern is repeated in nine major tributaries of the Amazon basin. 2. Adult Mylossoma aureum, M. duriventre, Colossoma macropomum, Anodus elongatus, Triportheus elongatus, Brycon cephalus, Semaprochilodus insignis, S. taeniurus and Prochilodus nigricans were recorded in nutrient‐poor and nutrient‐rich rivers. However, larval and juvenile individuals of these species were found in nutrient‐rich rivers only, indicating that spawning activity was restricted to that river type. 3. Concentration of suspended solids in the river was correlated with total ichthyoplankton density and related to species composition of juvenile characiform assemblages. 4. Our findings reinforce the hypothesis that nutrient‐rich rivers and associated floodplains function as spawning and nursery grounds, and suggest that they function as source habitats for these species in the Amazon Basin.     

Population trends of breeding birds in British woodlands over a 32-year period: relationships with food, habitat use and migratory behaviour

This paper outlines population trends (with confidence intervals) for 49 species in woodland habitats in Britain as monitored by the British Trust for Ornithology's (BTO) Common Bird Census (CBC) between 1967 and 1999. Additionally, the possible causes of these population trends are investigated by relating the ecological characteristics of species to the degree of population change they have undergone over different time periods. Over the whole period, 17 species showed significant decreases in abundance and 12 species showed significant increases. Whilst population trajectories were diverse, long-distance migrants showed more negative trends than other species and the timing of the changes in their populations was related to their wintering latitude, suggesting that these species may be suffering from environmental changes in the non-breeding season. There was also support for habitat specializations being related to population changes, with species classified as scrub and understorey specialists declining on average, but this was only evident across the entire study period. Additionally, species eating seeds in summer declined and those eating vegetation and making use of the agricultural landscape matrix increased. Therefore wide-scale factors such as landscape-scale processes or processes operating outside of Britain appear to be important in addition to local habitat change, especially for long-distance migrants.     

Multiple Paternity in the Nurse Shark, Ginglymostoma Cirratum

For over a decade, we have been studying the reproductive behavior of the nurse shark, Ginglymostoma cirratum, in the Dry Torugas off the Florida Keys, an important mating and nursery ground for this species. In the course of these studies, we have used a variety of tags and tagging protocols to monitor individual animals. Here we report the use of molecular methods for the genetic analysis of nurse sharks. Specifically we have analyzed genetic variation at the MHC II alpha locus using the polymerase chain reaction (PCR) followed by restriction fragment length polymorphism (RFLP) analysis of the amplified products. We found this technique to be a relatively rapid and reliable method for identifying genetic differences between individual sharks. Applying this method to a family of sharks consisting of a mother and 32 pups, we demonstrate that at least four fathers must have fathered this brood. Multiple paternity in the nurse shark suggests a mechanism by which populations of this species may maximize genetic variability. This seems especially valuable for philopatric species whose migratory movement, and thus potential for genetic diversity, is limited.     

Features of Temporal Differentiation of the Chum Salmon Oncorhynchus ketaof the Anadyr Bay Region at Different Abundance Levels

The temporal heterogeneity of chum salmon stock of the Anadyr Bay region was investigated on the basis of a set of discrete external morphological features and fluctuating asymmetry level of some meristic structures. Differentiation of Anadyr Bay chum salmon during the spawning run was found to be associated with the abundance level of spawning stock in a particular year. Sharply pronounced temporal heterogeneity, based on the investigated characteristics, in the area near the river mouth can be considered as an indicator of the subsequent deficiency of spawners on the spawning grounds of rivers in the Anadyr Bay region.     

The decline of Afro‐Palaearctic migrants and an assessment of potential causes

There is compelling evidence that Afro‐Palaearctic (A‐P) migrant bird populations have declined in Europe in recent decades, often to a greater degree than resident or short‐distance migrants. There appear to have been two phases of decline. The first in the 1960s–1970s, and in some cases into the early 1980s, largely affected species wintering predominantly in the arid Sahelian zone, and the second since the 1980s has mostly affected species wintering in the humid tropics and Guinea forest zone. Potential drivers of these declines are diverse and are spread across and interact within the migratory cycle. Our knowledge of declining species is generally better for the breeding than the non‐breeding parts of their life cycles, but there are significant gaps in both for many species. On the breeding grounds, degradation of breeding habitats is the factor affecting the demography of the largest number of species, particularly within agricultural systems and woodland and forests. In the non‐breeding areas, the interacting factors of anthropogenic habitat degradation and climatic conditions, particularly drought in the Sahel zone, appear to be the most important factors. Based on our synthesis of existing information, we suggest four priorities for further research: (1) use of new and emerging tracking technologies to identify migratory pathways and strategies, understand migratory connectivity and enable field research to be targeted more effectively; (2) undertake detailed field studies in sub‐Saharan Africa and at staging sites, where we understand little about distribution patterns, habitat use and foraging ecology; (3) make better use of the wealth of data from the European breeding grounds to explore spatial and temporal patterns in demographic parameters and relate these to migratory pathways and large‐scale patterns of habitat change and climatic factors; and (4) make better use of remote sensing to improve our understanding of how and where land cover is changing across these extensive areas and how this impacts A‐P migrants. This research needs to inform and underpin a flyway approach to conservation, evaluating a suite of drivers across the migratory cycle and combining this with an understanding of land management practices that integrate the needs of birds and people in these areas.