云南大山包越冬黑颈鹤调查简报

云南大山包是昭通市辖区西部79km的一个乡,属高原缓丘草甸地貌的贫困农牧业高寒山区,是近二年新发现的国家一类保护动物黑颈鹤(Grus nigricollis)分布数量最大的越冬地。在这里越冬的黑颈鹤主要栖息在跳礅河水库和大海子水库。1990年2月,进行多次分组同步调查结果,计有黑颈鹤181只。其中跳礅河稳定栖息的为141只,种群结构为2只亲鸟带2只幼鹤的家庭2家,2只亲鸟带1只幼鹤的家庭8家,配对的非繁殖成鹤家庭11家,孤成鹤2只,亚成鹤85只。另有11只灰鹤。大海子稳定栖息的为40只,种群结构仅有2只亲鸟带1只幼鹤的1家,余下的37只均为亚成鹤。另计有2只…     

贵州草海湿地越冬黑颈鹤觅食地与农耕地的空间关系研究

贵州草海湿地是世界上最大的黑颈鹤东部种群越冬地之一。黑颈鹤在草海越冬期极其依赖农耕地觅食存活,但当地人鸟争地冲突严重、觅食地萎缩加剧。为此,运用空间点格局分析及缓冲区叠加分析,探究黑颈鹤觅食地与农耕地空间关联性,并精确确定出重点保护管理区域,结果表明：1）研究期间,两年共在草海湿地周边农地确定黑颈鹤觅食点216处,其中家庭鹤觅食地99处、集群鹤觅食地117处,越冬种群中83%的个体依赖农耕区觅食;2）区域尺度上,家庭鹤与集群鹤的觅食点分布均为聚集分布,但集群鹤觅食点聚集程度较家庭鹤更高;觅食地与农耕地在空间聚类上呈正相关关系,并在3.2 km距离尺度下聚类程度最高;3）基于空间关联性,通过缓冲区叠加分析,共确定最适宜的农地觅食地53.74 km²,并划定2处重点核心保护区域及2处次重核心保护区域范围。研究结果对于揭示区域尺度上黑颈鹤觅食地与农耕地空间关系,指导保护管理者加强重点区域管理,以及对区域土地利用规划和缓解人鸟争地矛盾,具有重要的理论与实践意义。     

贵州草海越冬黑颈鹤飞出飞回夜栖地行为节律初步观察

野生动物行为节律常常是其对环境变化的一种行为适应。黑颈鹤(Grus nigricollis)越冬期会利用固定夜栖地,形成每天早晨飞出觅食,傍晚飞回夜栖的固定行为模式。为探索这一固定行为模式在越冬不同时期的变化及其影响因素,利用瞬时扫描法对草海湿地全部7个固定夜栖地的黑颈鹤飞出和飞回夜栖地准确时间及飞出之前和飞回之后在夜栖地的行为节律进行了观察。并且保证越冬前期(11月9日至12月31日)、中期(1月1日至2月21)和后期(2月22日至3月31日)3个阶段的调查时间分别不低于15 d。结果表明,越冬不同时期黑颈鹤飞出夜栖地时间差异极显著(F=23.38,P0.01),飞回夜栖地时间存在显著性差异(F=3.51,P0.05)。整个越冬期,黑颈鹤飞出夜栖地时间在中期延后,而到后期则更为提前,越冬前期、中期和后期飞出夜栖地的平均时间分别为7:34时、7:40时和7:13时;而飞回夜栖地时间逐渐延后,平均时间由前期的17:12时,至中期的17:40时和后期的18:15时。黑颈鹤飞出夜栖地之前的行为在越冬前期、中期和后期差异极显著(F=1 768.25,df=12,P0.01),飞回夜栖地之后的行为在前期、中期和后期差异亦极显著(F=793.98,df=12,P0.01)。越冬前期、中期和后期,黑颈鹤飞出夜栖地之前的行为与飞回夜栖地之后的行为均差异极显著(前期F=2 723.16,df=6,P0.01;中期F=1 979.48,df=6,P0.01;后期F=5 098.18,df=6,P0.01)。黑颈鹤在飞出夜栖地前的80 min内,其行为以保养(34.32%)和休息(32.38%)为主;而飞回夜栖地后的90 min内,以觅食(43.04%)和休息(23.68%)为主。飞出时刻与日出时刻呈显著强相关(r=0.832,n=48,P0.01),飞回时刻与日落时刻呈弱相关(r=0.353,n=47,P0.01)。日出时间与黑颈鹤飞出夜栖地的时间的差值(Y1)受飞离时的空气湿度(W)影响,二者成反比,Y1=0.469﹣0.625W,P0.05。黑颈鹤飞回夜栖地时刻与日落时刻的差值(Y2)受当天平均温度(T)的影响较为显著,Y2=1.231﹣0.107T,P0.05,当天平均温度越高黑颈鹤飞回夜栖地时间越早,温度越低,黑颈鹤飞回夜栖地的时间越晚。研究结果对于进一步探讨黑颈鹤完整夜栖行为及其对干扰的适应性具有重要意义。     

云南纳帕海越冬黑颈鹤日间行为模式与年龄和集群的关系

2006年10月—2007年5月,在云南省西北部纳帕海,采用路线调查结合瞬时扫描行为取样法,对越冬黑颈鹤(Grus nigricollis)种群的时间分配及其与年龄、集群和时间的关系进行了观察。结果说明,黑颈鹤越冬活动主要是以觅食为主,占日间时间的(76.81±9.1)％。越冬期间黑颈鹤日间行为的节律性较为明显,具有适应高寒气候的特点。集群形式对成鹤的行为有着显著影响,集群和家庭中活动的成鹤在觅食、警戒和争斗中存在显著差异(F1,76= 0.27、0.77, U= 279, P= 0.001—0.000)。年龄是影响鹤群行为的因素之一。幼鹤相比成鹤有较多的觅食时间和休息时间,警戒行为比例较低(F1,76= 0.04—2.59, U= 188—299, P= 0.006—0.000),且不受集群形式的影响。随着越冬期间的早、中、晚3个时期的环境变化,黑颈鹤的时间分配有显著变化(F2,36= 4.63—26.54, 22= 5.29—13.68, P= 0.0016—0.000)。不同越冬地的黑颈鹤行为存在差异。气候、食物资源和人为影响可能是造成这些差异的主要因素。     

东昆仑-阿尔金山地区黑颈鹤种群分布与秋季数量变化

黑颈鹤(Grus nigricollis)是青藏高原特有物种,在新疆主要分布在与青海、西藏相邻的阿尔金山、东昆仑山地区。2011年9～11月,对该地区黑颈鹤的分布、种群大小、数量变化、生存状况等进行了详细调查。在乌尊硝尔、铁木里克乡、玉素甫阿勒克、鸭子泉、阿达滩、祁曼塔格乡、吐拉牧场等25个样点,都观察到有黑颈鹤分布。利用样点调查法和直接计数法,重复调查164次,共记录到黑颈鹤158只。其中,在依协克帕提湿地(N37°15'～37°23',E90°11'～90°20',海拔3 903 m)最多一次记录到126只黑颈鹤集群。结合早期的科学考察记录,推测在整个东昆仑-阿尔金山地区共有黑颈鹤220～260只左右。黑颈鹤家庭成员数量为1～4只,4种类型的家庭所占比例分别为5.9%、60.3%、29.4%和4.4%。在10月份之前,主要以家庭为单位活动;10月中旬,开始大规模集群,10月29日集群数量达到最高峰,并开始迁徙;11月6日黑颈鹤全部迁徙离开。此外,还观察到有少量的灰鹤(G.grus)和蓑羽鹤(Anthropoides virgo)与黑颈鹤混居在一起。     

鄱阳湖4种鹤类集群特征与成幼组成的时空变化

2014年10月—2015年4月,采用样点法对鄱阳湖45个样点的白鹤(Grus leucogeranus)、白头鹤(G.monacha)、白枕鹤(G.vipio)和灰鹤(G.grus)的集群大小、集群类型和成幼组成进行调查。结果显示,白鹤的平均集群大小(23.86±10.26)只(集群数N=104),白头鹤(6.42±1.63)只(N=98),白枕鹤(6.09±2.55)只(N=105),灰鹤(5.55±1.26)只(N=246)。仅白头鹤中期集群大小显著小于后期,其余鹤类各时期及灰鹤各地区的集群大小差异不显著。鄱阳湖鹤类的集群大小并不符合警戒行为对集群大小的预测,生境质量差异可能是影响鄱阳湖鹤类集群大小的主要原因之一。4种鹤类均在1—5只个体的小集群中出现频度最高。白鹤在35只个体集群中的个体比例最高,而白头鹤、白枕鹤和灰鹤在1—5只个体集群和35只个体集群均有较高的个体比例。白鹤、白头鹤、白枕鹤和灰鹤均以家庭群为主,其家庭群所占比例分别为(64.29%,总集群数N=98)、(71.91%,N=89)、(70.77%,N=65)和(63.11%,N=206)。鄱阳湖鹤类以家庭群为主表明,保证充足的食物供应可能比花费更多的觅食时间更为重要。白鹤家庭群以2成1幼为主(65.08%),白头鹤(51.56%)、白枕鹤(52.17%)和灰鹤(47.69%)以2成为主。白鹤、白头鹤、白枕鹤和灰鹤群体的幼鸟比例分别为12.27%(个体数N=1695)、14.42%(N=416)、16.59%(N=229)和20.46%(N=655)。2成2幼集群比例极低表明,白鹤家庭同时抚养2个幼鸟成活的难度较其它3种鹤类大。4种鹤类在各时期的幼鸟比例差异不显著。在灰鹤个体数较多的3个地区中,都昌候鸟省级自然保护区(25.25%)和东鄱阳湖国家级湿地公园(25.14%)的幼鸟比例分别显著和极显著地高于鄱阳湖国家级自然保护区(14.24%)。鄱阳湖白鹤的幼鸟比例多年来均处于较低水平,白头鹤的幼鸟比例较2012—2013年冬季明显下降,灰鹤和白枕鹤种群可能处于稳定或增长状态。     

黑颈鹤种群动态模型

本研究据已收集到的数据,用非参数统计方法确定了黑颈鹤种群的性比为1:1,避免了大量取样。根据黑颈鹤的特点,我们将其种群分成4个年龄组,并求出了各年龄组的存活率和繁殖率,据此建立了描述黑颈鹤种群动态的数学模型。用模型计算得出在乌蒙山区越冬的黑颈鹤种群的自然增长率为1.85‰;理想的种群结构为幼鹤、亚成鹤、成鹤、老鹤分别占总数的15.5％、21.5％、60.2％、2.8％,最后预测了乌蒙山黑颈鹤种群在1988～2000年越冬期的数量。1989年1月经实地调查该种群总数为310只,而预测值为303只,误差约2％。     

黑颈鹤越冬生态初步研究

黑颈鹤为我国特产珍稀动物,作者于1975和1978至1984年间,对它的越冬生态进行了观察。观察得知,黑颈鹤每年10月中、下旬迁来草海,翌年8月中下旬离去,越冬期为5个月左右。越冬期,有3种不同的集群形式,即家族群、同种集群和混种集群。主要食物为植物。黑颈鹤在草海越冬的数量,已由1975年的35只,增加到1984年的305只。黑颈鹤除在草海越冬外,还发现于威宁东南的普安县,是迄今所知在我国分布最南和最东的纪录。     

云南纳帕海越冬黑颈鹤夜栖地特征

2009年11月至2010年4月对云南省香格里拉县纳帕海省级自然保护区越冬黑颈鹤(Grus nigricollis)的夜栖地的特征进行了调查.采用三角定位标图结合标志物校正法确定夜栖地方位,并进行实地校正.共记录夜栖地63个,均位于有水的斑块状沼泽中,基底大多有泥层,大部分(81.0%)有植被覆盖.夜栖地与人类活动区域和沼泽岸边有一定距离.与随机对照样地相比,夜栖地基底泥层较厚(Z=-2.365,P=0.018),明水面比例较大(Z=-3.086,P=0.002),离道路、村庄和农田较远(Z/t=-2.852～-2.334,P=0.008～0.020),水深在两者间有极显著差异(χ2=16.730,P=0.001).夜栖地利用前后对比发现沼泽斑块的面积有显著差异(t=2.977,P=0.021).主成分分析表明影响黑颈鹤夜栖地利用的因素依次为人类干扰、沼泽斑块大小和浅水环境状况.     

江西鄱阳湖流域中华秋沙鸭越冬期间的集群特征

2010年11月—2011年3月,采用样线法对江西鄱阳湖流域8个河段的中华秋沙鸭Mergus squamatus的集群特征进行了研究。中华秋沙鸭的集群类型包括雄性群、雌性群、混合群、雌性孤鸭和雄性孤鸭5种类型。越冬期间共记录到89群次,432只次中华秋沙鸭。其中,混合群是最多的一种集群方式,孤鸭也是越冬期间出现频次较高的一种特殊的集群方式。集群类型存在时间变化(P<0.01)。混合群中,大多数群体中雌性个体数多于雄性个体或者是一雌一雄。89群次中,孤鸭和2—8只群占总群数的87.64%,提示中华秋沙鸭主要以集小群分散活动。中华秋沙鸭越冬期间的群体大小是(4.85±4.97)只/群。不同集群类型的群体大小差异较大。集群大小可能与采砂、捕鱼、食物的丰富度等环境因子有关。调查结果显示,中华秋沙鸭越冬期间的性比是1∶0.74(n=432)。中华秋沙鸭群体大小与性比有一定的关系。     

西藏拉萨越冬黑颈鹤家庭群的警戒同步性

以往关于动物警戒行为的研究多以经典随机独立模型为基础,然而,近期一些理论和实证研究则向该模型发出了挑战。根据警戒行为同步性程度的不同,集体警戒可能存在基于模仿的同步警戒和避免重复的协调警戒两种模式。研究了中国雅鲁藏布江自然保护区越冬黑颈鹤家庭群的警戒行为,通过独立样本t检验验证由于年龄和是否携幼所导致的个体警戒水平的差异,通过单因素方差分析比较不同类型家庭群的集体警戒水平,通过配对t检验比较集体警戒的实际观测值和独立假设下的预期值从而确定越冬黑颈鹤家庭群的警戒同步性。结果表明家庭群中的幼年黑颈鹤警戒行为时间显著低于成年黑颈鹤,但幼鹤的存在对成鹤的警戒水平没有显著影响。不同类型黑颈鹤家庭群的集体警戒水平没有差异,但并未如预期表现为同步警戒。警戒行为模式是动物在特定环境中的适应性表现,越冬黑颈鹤生境中不存在落后目标策略的捕食者和高强度的捕食风险,因而可能不足以诱发以降低捕食风险为主要功能的高强度的警戒行为同步性;同时,在资源匮乏的冬季对食物获取的优先性可能也削弱了对同步警戒的需求。     

Common cranesGrus grus and habitat management in holm oak dehesas of Spain

Changes in agricultural policies have favored tree clearing and removal of shrubs to favor intensive farming in the holm oakQuercus ilex dehesas of Iberia. The effect of these changes for bird species wintering in this agricultural landscape has been rarely analyzed. Here the effects are studied of farming changes in traditional holm oak dehesas on population size, social structure and time budget of common cranesGrus grus in eight traditional wintering sites in Spain. The role of acorn availability, the principal winter food of the species, in relation to management is also assessed. The number of cranes in each wintering area was not related to degree of agricultural intensification, nor to the availability of acorns. However, crane flock size decreased, and the relative occurrence of isolated family groups increased in less intensively transformed wintering areas characterized by the predominance of fallow lands. The age composition of crane flocks varied with acorn availability since more juveniles were reported in areas with relatively lower acorn availability. Time budget was also related to acorn availability, since cranes spent relatively more time preening in those wintering areas with higher availability of acorns. Globally evidence suggests the need to maintain the fallow land (posíos) to sustain the wintering populations of cranes in Iberia, since this agro-grazing system maintains most of the juvenile cranes using the western migratory route.     

How do vigilance and feeding by common cranes Grus grus depend on age,habitat, and flock size?

Animals often spend less time vigilant and more time feeding when foraging in larger groups. This group-size effect does not, however, consider if larger groups differ systematically from smaller ones: Large groups could form in different habitats than small groups or be composed of a different mix of ages or classes than small groups. We examined how habitat differences and flock size and composition explain feeding and vigilance rates in common cranes Grus grus , wintering in holm oak Quercus ilex dehesas of Spain. Flock size and composition were related to habitat type in cranes: flocks formed in areas sown with cereal crops were larger than flocks formed in set aside areas. Vigilance rate depended on habitat but decreased with increasing flock size in a similar way across all habitats. Juveniles were less vigilant than adults and showed little change in vigilance with flock size. Vigilance increased and feeding time decreased over months from November through February. Our results show that vigilance is affected by habitat but that the group size effect on vigilance is not the product of differences between habitats in group size or composition.     

若尔盖湿地保护区黑颈鹤巢期及影响因子

对鸟类巢期的研究不仅可以丰富鸟类繁殖生物学资料,也可为理解和研究鸟类的生态适应与进化提供重要线索和依据。2013—2014年3月份至7月份,在若尔盖湿地保护区及周边对55对繁殖黑颈鹤的营巢时长进行了研究,调查结果显示:黑颈鹤的营巢时长在0.5—40 d之间,平均巢期为(6.7±9.3)d;在其营造的4种巢型中,巢期长短依次为:泥堆巢草堆巢草墩巢岛地巢,且差异性极显著(P0.001),巢期与巢型显著相关(r=0.728);在其营巢的3种巢址生境中,巢期长短依次为:湖泊生境沼泽生境河流生境,且差异性极显著(P0.001),巢期与巢址生境显著相关(r=0.315);从不同营巢月份看,巢期长短依次为:4月份巢5月份巢6月份巢,且差异性极显著(P0.01),巢期与筑巢月份显著相关(r=0.664);巢期与巢体积大小具有显著相关性(r=0.856),即营巢时间越长巢体积越大。黑颈鹤的营巢时间长短主要受营巢生境、月份和做巢类型的影响。     

年龄、集群、生境及天气对鄱阳湖白鹤越冬期日间行为模式的影响

于2012年1—3月和2012年12—2013年3月,采用瞬时扫描法研究了鄱阳湖国家级自然保护区越冬白鹤(Grusleucogeranus)的昼间时间分配模式和日活动节律,分析了年龄、集群大小、生境类型和天气对白鹤越冬行为的影响。结果表明,白鹤越冬期的主要行为有觅食、警戒、理羽、游走、休息和争斗。其中,觅食是鄱阳湖越冬白鹤主要行为,占其昼间活动时间的82.94%;警戒占11.94%,理羽占3.52%,游走占1.88%,休息占0.15%,争斗占0.02%。白鹤在越冬期间的觅食、游走、休息和争斗行为存在明显的昼间节律性,其中游走、觅食和争斗行为在每天的上午和下午各存在1个高峰,休息行为在中午出现一个高峰;警戒和理羽行为则没有显著的昼间节律变化。年龄、集群大小、天气和生境对白鹤的越冬行为具有显著的影响:幼鹤取食的时间显著多于成鹤,而警戒时间则显著的小于成鹤;与家庭群中的个体相比,集体群中的个体取食和争斗时间显著增加,警戒时间显著减少;在天气晴朗时,白鹤的警戒时间显著大于阴天的警戒时间,取食时间则显著少于阴天时白鹤的取食时间;白鹤在大风天气显著增加理羽行为;在有雾的天气会显著增加取食时间,减少警戒时间。在草洲和浅水两种生境中,白鹤的游走和理羽行为存在显著差异,而觅食和警戒行为没有显著的差异,这可能源于草洲和浅水生境相互毗邻,并且具有相同程度的人为干扰。GLM分析结果表明,年龄和集群大小、年龄和生境、集群大小和天气、集群大小和生境、天气和生境对白鹤昼间时间分配模式的影响存在显著交互效应。     

Vigilance responding to number of conspecifics among mixed groups of cranes in demilitarized zone

Numerous studies have addressed antipredatory benefits of mixed-species flocks of foragers, but studies on individual's vigilance as a function of group size are limited. In the Cheolwon area of the Korean Demilitarized Zone, vigilance of the subordinate White-naped cranes (Grus vipio) in 11 groups composed of conspecifics and the dominant Red-crowned cranes (Grus japonensis) was examined. Vigilance correlated negatively with group size due to negative correlation with the number of conspecifics, but not the dominant heterospecifics. This is consistent with the hypothesis that a decrease in vigilance in larger groups is due to antipredatory benefits from increased predator detection in larger groups (associated with the presence of a larger number of conspecifics). This suggested that the mechanism leads to canceling out of the otherwise expected antipredatory benefits to the subordinate species from the increased predator detection by larger group size (associated with larger number of dominants). This is one of only a few behavioral studies of these endangered crane species in the relatively inaccessible wintering area of international importance in the areas of high conservation value.     

Space use and site fidelity of wintering whooping cranes on the Texas Gulf Coast

The Aransas-Wood Buffalo population (the only non-reintroduced, migratory population) of endangered whooping cranes (Grus americana) overwinters along the Texas Gulf Coast, USA. Understanding whooping crane space use on the wintering grounds reveals essential aspects of this species' ecology, which subsequently assists with conservation. Using global positioning system telemetry data from marked whooping cranes during 2009–2017, we fit continuous-time stochastic process models to describe movement and home range using autocorrelated kernel density estimation (AKDE) and explored variation in home range size in relation to age, sex, reproductive status, and drought conditions. We used the Bhattacharyya coefficient of overlap and distance between home range centroids to quantify site fidelity. We examined the effects of time between winter home ranges and the sex of the crane on site fidelity using Bayesian mixed-effects beta regression. Winter whooping crane 95% AKDE home range size averaged 30.1 ± 45.2 (SD) km² (median = 14.3, range = 1.1–308.6). Home ranges of sub-adult females were approximately 2 times larger than those of sub-adult males or families. As drought worsened, home ranges typically expanded. Between consecutive years, the home ranges of an adult crane exhibited 68 ± 31% overlap (site fidelity), but fidelity to winter sites declined in subsequent winters. The overlap of adult home ranges with the nearest unrelated family averaged 33 ± 28%. As a whooping crane aged, overlap with its winter home range as a juvenile declined, regardless of sex. By 4 years of age, a whooping crane had approximately 14 ± 28% overlap with its juvenile winter home range. Limited evidence suggested male whooping cranes return to within 2 km of their juvenile home range by their fifth winter. Previous data obtained from aerial surveys led ecologists to assume that whooping crane families normally used small areas (~2 km²) and expressed persistent site fidelity. Our analyses showed <8% of families had home ranges ≤2 km², with the average area 15 times greater, and waning site fidelity over time. Our work represents an analysis of whooping crane home ranges for this population, identifying past misconceptions of winter space use and resulting in better estimates of space requirements for future conservation efforts.     

Allozyme evidence for crane systematics and polymorphisms within populations of Sandhill, Sarus, Siberian, and whooping cranes.

Electrophoretic analysis of proteins yielded evidence on the relationships of species of cranes and on genetic diversity within populations of some species. Diversity within the Greater Sandhill crane and a Florida population of the Florida Sandhill crane was similar to that of most other vertebrates, but diversity was low in the Mississippi Sandhill crane, in the Okefenokee population of the Florida Sandhill crane, and within the Siberian and Sarus cranes. Diversity was surprisingly high among whooping cranes, whose number dropped to less than 25 early in this century. Phylogenetic analysis, using both character state and distance algorithms, yielded highly concordant trees for the 15 species. The African crowned cranes (Balearica) were widely divergent from all other cranes. Species of Anthropoides, Bugeranus, and Grus clustered closely but sorted into two lineages: a Whooper Group consisted of the whooping, common, hooded, black-necked, white-naped, and red-crowned cranes of genus Grus; and a Sandhill Group included the Sandhill, Siberian, Sarus, and Brolga cranes of genus Grus, the wattled crane of genus Bugeranus, and the Demoiselle and blue cranes of genus Anthropoides.     

Collective Vigilance in the Wintering Hooded Crane: The Role of Flock Size and Anthropogenic Disturbances in a Human‐Dominated Landscape

Vigilance achieved at the group level, known as collective vigilance, can enhance the ability to assess threats and confer benefits to gregarious prey species. Examining the factors that influence collective vigilance and exploring how individual vigilance is organized at the group level can help to understand how prey groups respond to potential threats. We quantified collective vigilance and determined its temporal pattern in a natural wintering population of the hooded crane Grus monacha in the Shengjin Lake reserve in China. We examined the role of flock size and anthropogenic disturbances in the human‐dominated landscape on collective vigilance and level of synchronization. The proportion of time during which at least one individual scanned the surroundings (collective vigilance) increased with flock size and was higher in the more disturbed buffer zone of the lake. Synchronization of vigilance occurred more frequently in the smaller flocks but was not related to the risk of disturbance. Synchronization implies that individuals tend to monitor and copy the vigilance of neighbors. In the degraded wetlands, the wintering hooded crane benefits from foraging in groups and synchronizing their vigilance in response to human disturbances.     

群体规模对越冬灰鹤警戒行为的影响

2005年1—3月,在云南丽江拉市海就群体规模对越冬灰鹤(Grusgrus)警戒行为的影响进行了研究。用扫描取样记录群体的规模和警戒个体的数量、用焦点取样记录群体中个体警戒行为的频次和持续时间,结果显示灰鹤群体和个体的警戒力均随群体规模增加而降低,但集群个体数超过30只后,群体警戒力便不会再下降(P>0.05)、成体的警戒持续时间也会增加(P<0.01);当群体规模超过50只后,成体的警戒频次也会上升(P<0.05)。推测亚成体维持低警戒的群体规模上限值要高于成体,单从警戒行为分析,20—30只个体的集群可能代表越冬灰鹤的最适群体大小。