大鸨的巢位选择研究

2000年和2001年的4～7月连续两年,在内蒙古自治区科尔沁右翼前旗东南部草原上采用野外直接观测和样方法对繁殖期大鸨(Otis tarda)的巢位选择进行了研究.结果表明,大鸨是一种营地面松散型群巢的大型鸟类,最近巢间距为9m.大鸨在繁殖期对巢位具有明显的选择性:首先表现在景观尺度上的选择,大鸨巢多筑在海拔190～230m的草原岗坡的坡腰上,以偏南向的朝阳缓坡的坡腰上为多,最大坡度不超过8°,而且巢均筑在距车道不远的地方;其次表现在植被结构上的选择,大鸨倾向于选择枯草较厚、植被密度较高且多数植物高度在15～35cm的地方营巢,但植被密度过高处却并不选择.     

大鸨求偶场的选择

20 0 0年和 2 0 0 1年的 4～ 7月 ,在吉林省西北部和内蒙古东北部草原地带 ,采用观察法及样方法对大鸨 (Otis tardadybowskii)的求偶炫耀行为及求偶场选择进行了研究。结果表明 :大鸨具有集群炫耀的特点 ,雄鸨一天之中有两个求偶炫耀高峰期 ,上午为 7:0 0～ 9:0 0 ,下午为 16 :0 0～ 17:30 ,下午的炫耀强度较早晨略弱。求偶场选择在坡度平缓、视野开阔的草原岗坡的下坡腰和坡底 ,而且是在土质松软、土壤颗粒较细的地方。草原火烧对其求偶场选择具有一定影响。在火烧地 ,高度为 2 0～ 30 cm植物所占比例、植物种类数、植被盖度、植物均高和线叶菊密度是主要因子 ;在非火烧地 ,枯草比例和枯草厚度是重要因子 ;综合来看 ,在植被结构上 ,其求偶场主要选择在植物种类丰富、植株相对较高及裸地比例和地面枯草厚度较小处     

芜湖市及附近地区三种鹭鸟巢址特征

2005年,对芜湖市及附近地区4个营巢地的3种主要营巢鹭鸟--白鹭(Egretta garzetta)、夜鹭(Nycticorax nycticorax)和池鹭(Ardeola bacchus)的巢址特征进行了抽样调查,选取了11个巢址变量,即营巢树种、巢高、巢树高、巢上方郁闭度、巢周围1m半径内植被郁闭度、巢树胸径、巢离树干距离、巢下最大支撑枝直径、巢离巢区边缘的距离、坡位、巢位海拔,运用单因素方差分析和主成分分析方法研究3种鹭乌的巢址特征.结果表明,巢位因子、巢树因子、保护因子、坡位因子等4个主成分描述了3种鹭鸟的巢址特征,其贡献率分别为25.51%、24.42%、13.19%和12.32%.影响鹭鸟巢址选择的最主要因素是微栖息地适合度和巢捕食压力.     

大鸨繁殖期觅食地的选择

2000年和2001年的4～7月,在内蒙古自治区科尔沁右翼前旗东南部的草原地带,采用样方法研究了火烧地和非火烧地上繁殖期大鸨的觅食地选择.结果表明,在火烧地和非火烧地,大鸨觅食地的植株高度均为13cm左右,最高高度不超过30cm,植被结构上具有共性;植物种类丰盛密集,盖度较大,喜食的植物和昆虫丰富.但在喜食食物选择上,火烧对大鸨有一定影响.在非火烧地,大鸨多关注动物性食物的丰盛;而在火烧地则关注植物性食物的丰盛.     

大鸨繁殖期觅食地的选择

2000年和2001年的4～7月,在内蒙古自治区科尔沁右翼前旗东南部的草原地带,采用样方法研究了火烧地和非火烧地上繁殖期大鸨的觅食地选择.结果表明,在火烧地和非火烧地,大鸨觅食地的植株高度均为13cm左右,最高高度不超过30cm,植被结构上具有共性;植物种类丰盛密集,盖度较大,喜食的植物和昆虫丰富.但在喜食食物选择上,火烧对大鸨有一定影响.在非火烧地,大鸨多关注动物性食物的丰盛;而在火烧地则关注植物性食物的丰盛.     

栗斑腹鵐的栖息地和巢址选择

于 1 999到 2 0 0 1年 5月至 7月连续 3a在吉林省镇赉县大岗林场 ,采用样地法和样方法 ,对栗斑腹的栖息地选择和巢址选择进行了研究。结果表明 :此鸟的繁殖是在草甸草原 杏树环境下进行的 ,对栖息地样方和对照样方的对比分析得出 ,杏树最大高度、5 0 m半径圆内杏树数量、贝加尔针茅数量、大油芒数量、植物盖度、火绒草平均高度、贝加尔针茅最大高度、兴安胡枝子平均高度 8个因子是影响其栖息地选择的主要因子。通过对 46个巢的研究发现 ,大多数栗斑腹把巢建在贝加尔针茅下面 ,巢出入口方向多为东南 45°和西南 45°。对 46巢的 2 7个因子的主成分分析 ,结果发现植物盖度、火绒草高度、鸢尾数量、巢出入口方向、1 0 m内杏树数量、30 m内杏树数量、裸地面积这 6个因子是巢址选择的主要因子。对 46巢 2 6个巢址和非巢址因子进行判别分析 ,植物盖度、大油芒、乳浆大戟高度、石竹数量、线叶菊高度和 30 m内杏树数量等 6个因子 ,为巢位选择的主要因子。两种分析结果基本相似。总之 ,栗斑腹喜欢在植被盖度大、杏树相对多、贝加尔针茅和大油芒的密度大、食物资源丰富的区域内营巢。     

内蒙古草原繁殖鸟类群聚组成之比较

利用 5月份温带草原鸟类繁殖期 ,在荒漠草原、草原、湿地、沙地和山地等植被 ,选取 1 1个面积 1 0 0 hm2 ( 50 0 m×2 0 0 0 m)同样大小的样区 ,由 3人各隔 1 50 m作平行的穿越线调查 ,并记录所见鸟类的种类与数量。同时 ,也在每一样区任取面积 1 m2 之植被样方 ,记载样方内植物的种类、垂直高度、覆盖度和植物鲜重。调查结果显示草原繁殖鸟类的种类不多 ,在无树的荒漠草原植被是 4～ 6种 ,草原植被在 5～ 8种之间 ,湿地植被 1 5种 ;在有树的沙地植被是 9～ 1 2种 ,山地植被 6种。鸟种多样性和丰富度指数不大 ,由大而小依序是沙地植被、湿地植被、山地植被、草原植被、荒漠草原植被 ;密度也不高 ,由大而小依序是无树草原的湿地植被、草原植被、荒漠草原植被 ,而后是有树草原的沙地植被、山地植被。鸟类食性分布方面 ,荒漠草原和草原植被以食杂性鸟类为优势 ;湿地植被以食虫性鸟类为多 ;沙地植被以食杂与食肉性鸟类为胜 ;山地植被以食虫和食杂性鸟类较多 ,并增加一些食肉性鸟类。     

栗斑腹鹀的栖息地和巢址选择

于1999到2001年5月至7月连续3a在吉林省镇赉县大岗林场,采用样地法和样方法,对栗斑腹鹀的栖息地选择和巢址选择进行了研究.结果表明此鸟的繁殖是在草甸草原+杏树环境下进行的,对栖息地样方和对照样方的对比分析得出,杏树最大高度、50 m半径圆内杏树数量、贝加尔针茅数量、大油芒数量、植物盖度、火绒草平均高度、贝加尔针茅最大高度、兴安胡枝子平均高度8个因子是影响其栖息地选择的主要因子.通过对46个巢的研究发现,大多数栗斑腹鹀把巢建在贝加尔针茅下面,巢出入口方向多为东南45°和西南45°.对46巢的27个因子的主成分分析,结果发现植物盖度、火绒草高度、鸢尾数量、巢出入口方向、10 m内杏树数量、30 m内杏树数量、裸地面积这6个因子是巢址选择的主要因子.对46巢26个巢址和非巢址因子进行判别分析,植物盖度、大油芒、乳浆大戟高度、石竹数量、线叶菊高度和30m内杏树数量等6个因子,为巢位选择的主要因子 .两种分析结果基本相似.总之,栗斑腹鹀喜欢在植被盖度大、杏树相对多、贝加尔针茅和大油芒的密度大、食物资源丰富的区域内营巢.     

人造园林中斑文鸟和白腰文鸟的巢址选择

巢址选择对保证鸟类生存和繁殖成功、降低被捕食率和种间竞争至关重要。2016—2017年,在中国科学院西双版纳热带植物园选取3个研究区域对同域分布的斑文鸟Lonchura punctulata和白腰文鸟Lonchura striata进行调查。在记录的15个巢址特征因子中,14个数值型因子用于拟合Logistic回归模型,找出影响文鸟巢址选择的关键因子;使用独立样本t检验和Mann-Whitney U检验比较2种文鸟在巢址特征因子选择上的差异性;置换检验(Permutation test)用于检验2种文鸟对营巢树种选择偏好的差异性。研究发现,2种文鸟的巢址分布模式在3个研究区域中的差异很大。异种鸟巢间最小间距、营巢树胸径、营巢树与水源最近距离以及巢位高度都是影响巢址选择的关键因子。与白腰文鸟相比,斑文鸟通常选择在胸径更小、位置更高、距离异种鸟巢更远、距离水源更近的地方营巢。斑文鸟多选择枝条紧密的树,而白腰文鸟多选择枝干带刺的树营巢,这可能是二者不同的对抗捕食者的防御策略。     

黄腹角雉的巢址选择

１９９１￣１９９３年，在浙江省乌岩岭自然保护区对黄腹角雉的巢址选择进行了研究。野外工作共发现黄腹角雉巢１５个，其中８０％位于人工柳杉林中，营果树以柳杉为主，占７３．３％。主成分分析表明，影响黄腹角雉巢址选择的主要因素有４种，依次为：营巢树因素（包括营巢树的高度、胸径、巢位高度和巢上方的植被盖度）、地形因素（包括坡向和坡度）、海拔因素和位置因素。     

斑翅山鹑巢址选择的研究

１９９１－１９９３年在山西宁武县对斑翅山鹑的巢址选择进行了研究,野外工作中共发现６０个巢,其中绝大多数位于远离林地的农田或灌丝地带,６６．６７％的巢位于向阳的东南坡和西南坡上,对巢址与随机选取的非巢样点所进行的对比分析发现,在１２个栖地参数中,影响巢址选择的５个因素依次为：落叶的数量、地缘宽度、干草的数量、灌丛宽度和梯田高度,判别分析的结果表明,落叶的数量和干草的数量是区别巢址与非巢样点的两个最重     

白尾地鸦的巢址选择

2017年4和5月,在位于新疆塔克拉玛干沙漠南缘的和田地区民丰县对白尾地鸦（Podoces bidduphi）的巢址选择进行研究。共记录白尾地鸦巢12个,测量了巢参数,用Mann-Whitney U检验分析巢样方与对照样方的差异,用主成分法分析影响白尾地鸦巢址选择的主要因子。结果显示：1）白尾地鸦巢多筑于绿洲边缘的柽柳（Tamarix）灌丛,巢距地面高（109.1 ± 13.2）cm,巢深（8.5 ± 0.5）cm,巢厚（3.8 ± 0.4）cm,内径（13.9 ± 0.9）cm,外径（21.6 ± 1.3）cm;2）巢样方的植被物种数和植被盖度远高于对照样方;3）影响白尾地鸦巢址选择的主要因素为植被物种数及干扰,其中干扰主要指距道路以及距居民点的距离。综上所述,白尾地鸦的巢址选择受食物等生存需求和躲避干扰等安全因素的双重影响,是生存与繁殖权衡的结果。     

Nest‐site selection and productivity of Vesper Sparrows breeding in grazed habitats

ABSTRACT Livestock grazing in the shortgrass steppe of the Intermountain region of British Columbia may have a negative impact on ground‐nesting birds, but evidence of such an impact is lacking. We examined nest‐site selection and productivity of ground‐nesting Vesper Sparrows (Pooecetes gramineus) across sites with different grazing histories. From 2006 to 2008, we monitored Vesper Sparrow nests and measured vegetation characteristics known to be affected by grazing within nest patches. We used an information‐theoretic approach to test the relative importance of grazing‐affected vegetation variables as predictors of nest‐site selection, nest survival, and nestling condition. Vesper Sparrows selected nest sites with greater cover of late‐seral grass species that decrease in occurrence in response to grazing (i.e., “decreasers”) than was available in random patches in the same territories. Daily nest survival was also lower for nests surrounded by shorter vegetation (odds ratio = 1.12). However, “decreaser” cover was not associated with either of the two indices of productivity measured (daily nest survival probability and nestling condition). In addition, vegetation height, although an important driver of success, was not linked with nest‐site selection, and no vegetation‐cover variable was positively associated with productivity, despite nest concealment being central to our predictions. This suggests that predation risk for nests in areas with shorter vegetation was being elevated through some factor unrelated to concealment. Our results show that grazing reduced both the availability of suitable habitat for and nesting success of Vesper Sparrows, indicating that grazing could pose a threat to population persistence at a broader scale and could potentially contribute to observed declines. Additional research is needed to determine if grazing guidelines in the Intermountain region of British Columbia should be amended, better enforced, or both to prevent regional declines in populations of ground‐nesting grassland birds.     

A description of nesting behaviors,including factors impacting nest site selection,in black‐and‐white ruffed lemurs (Varecia variegata)

Nest site selection is at once fundamental to reproduction and a poorly understood component of many organisms’ reproductive investment. This study investigates the nesting behaviors of black‐and‐white ruffed lemurs, Varecia variegata, a litter‐bearing primate from the southeastern rainforests of Madagascar. Using a combination of behavioral, geospatial, and demographic data, I test the hypotheses that environmental and social cues influence nest site selection and that these decisions ultimately impact maternal reproductive success. Gestating females built multiple large nests throughout their territories. Of these, females used only a fraction of the originally constructed nests, as well as several parking locations as infants aged. Nest construction was best predicted by environmental cues, including the size of the nesting tree and density of feeding trees within a 75 m radius of the nest, whereas nest use depended largely on the size and average distance to feeding trees within that same area. Microhabitat characteristics were unrelated to whether females built or used nests. Although unrelated to nest site selection, social cues, specifically the average distance to conspecifics’ nest and park sites, were related to maternal reproductive success; mothers whose litters were parked in closer proximity to others’ nests experienced higher infant survival than those whose nests were more isolated. This is likely because nesting proximity facilitated communal crèche use by neighboring females. Together, these results suggest a complex pattern of nesting behaviors that involves females strategically building nests in areas with high potential resource abundance, using nests in areas according to their realized productivity, and communally rearing infants within a network of nests distributed throughout the larger communal territory.     

Vegetation phenology and nest survival: Diagnosing heterogeneous effects through time

Birds should select nest sites that minimize predation risk, but understanding the influence of vegetation on nest survival has proven problematic. Specifically, the common practice of measuring vegetation on nest fate date can overestimate its effect on nest survival, simply because vegetation at hatched nests grows for a longer period of time than vegetation at nests that were depredated. Here, we sampled the literature to determine the prevalence of this bias in studies of duck breeding ecology. We then used survival data collected from ~2,800 duck nests to empirically evaluate evidence of bias in four different vegetation metrics: vegetation density measured when the nest was found, density when the nest was fated, and date‐corrected regression residuals of these two. We also diagnosed the magnitude of vegetation effects on nest survival by restricting our analysis to only nests which were fated contemporaneously (thereby removing potential bias in the timing of measurement). Finally, we examined whether systematic phenological differences exist between vegetation at hatched and depredated nests that have the potential to further obfuscate the relationship between vegetation and nest survival. We found evidence for a true‐positive effect of vegetation density on nest survival that appeared to be inflated when using raw vegetation measurements collected at fate date. However, taken in combination with the literature review, our results suggest that the majority of duck nesting studies have evaluated the role of vegetation on nest survival using a relatively less biased metric—vegetation density when the nest was found. Finally, we found that over the course of a nesting attempt, vegetation increased in density at successful nests, but decreased in density at depredated nests. As a consequence, duck researchers using vegetation data collected when the nest was found may actually be underestimating the magnitude of the effect. This seasonal change potentially points to an important new metric for understanding predation risk, but further experimental research is required to fully eliminate potential biases in the timing of vegetation measurements.     

Relationships between grazing and waterfowl production in the Canadian prairies

The survival of waterfowl nests is positively correlated with the amount of grassland on the landscape, and population growth rates of some waterfowl species (e.g., mallards [Anas platyrhynchos]) are sensitive to nest survival rates. Thus, the effect of actions that alter grassland vegetation physiognomy, such as grazing, on waterfowl production is of interest to waterfowl habitat managers. Additionally, grasslands contribute other ecological goods (e.g., forage for livestock and wildlife) and services (e.g., photosynthesis, carbon sequestration), which can be influenced by grazing practices. We address key uncertainties about the linkages between grazing, vegetation physiognomy, and the survival and density of duck nests at study-site, field, and nest-site spatial scales. Using data from 2,554 duck nests found in 434 grazed or idled fields (median field size = 48.0 ha) in the Canadian Prairie Pothole Region between 2002 and 2009, we found that vegetation physiognomy affected nest survival at both the field and nest-site scales, such that nest survival increased with nest-site vegetation density and late-season field vegetation density. Nest survival also responded to early-season within-field variation in vegetation height in a quadratic manner, such that survival was greatest in fields with moderate variation in vegetation height. Nest survival was negatively related to the intensity of grazing and to the amount of cropland in the surrounding landscape. Both the abundance of wetlands and the average vegetation height in the field had a positive influence on nest density. Fields idled during the breeding season had greater densities of nests than fields grazed either early or late in the breeding season. Leaving lands idled may be the most effective way to increase both waterfowl nest survival and nest density. When management of upland vegetation is required, we recommend grazing at moderate stocking rates (between 2 and 2.5 animal unit months [AUM]/ha) after the waterfowl breeding season is complete and monitoring vegetative characteristics to ensure they remain suitable to attract nesting waterfowl (e.g., leaving vegetation height >28 cm). Where grazing must be carried out during the breeding season, low to moderate stocking rates should be encouraged as these rates appear to have the least negative impact on both waterfowl nest survival and nest density. These stocking rates also will maintain rangeland in good condition to the long-term benefit of producers. © 2013 The Wildlife Society.     

RELATING GROUSE NEST SUCCESS AND CORVID DENSITY TO HABITAT: A MULTI-SCALE APPROACH

Abstract: Predators are the major cause of nest failure for prairie grouse, and corvids are widespread generalist predators that exploit land altered by humans where grouse are found. We studied how human-caused habitat change affected predator and prey by using habitat variables to model nest selection, corvid density, and nest success for sharp-tailed grouse (Tympanuchus phasianellus) in Alberta, Canada, 1999–2001. Habitat was quantified over a range of extents (radius of observation) from 2 to 2,265 m. We predicted that habitat features associated with corvid density at broad extents would also relate to grouse nest success, and that nesting cover and the presence of avian predator perch sites would be important at smaller extents. Corvid density was higher in landscapes with higher proportions of crop and sparse grassland (1,600-m extent). Conversely, nest success was markedly higher (≥4 times) in landscapes with <10% crop and <35% crop and sparse grassland (aggregated) at broad extents (1,600 m). Moreover, nests were 8 times more likely to succeed in landscapes with lower relative corvid densities (<3 vs. ≥3 corvids/km²). At smaller scales, nests were more likely to succeed with greater heights of concealment cover within 50-m of nests. Land managers can likely improve nest success for grouse in grassland systems by targeting concealment cover heights of at least 13 cm measured over a 50-m extent, and focusing efforts in landscapes with <10% crop and <35% crop and sparse grassland (1,600-m extent).     

The nest predator community of grassland birds responds to agroecosystem habitat at multiple scales

Nest predation is the leading cause of reproductive failure for grassland birds of conservation concern. Understanding variation in nest predation rates is complicated by the diverse assemblage of species known to prey on nests. As part of a long‐term study of grassland bird ecology, we monitored populations of predators known to prey on grassland bird nests. We used information theoretic approach to examine the predator community's association with habitat at multiple scales, including local vegetation structure of grassland patches, spatial attributes of grassland patches (size and shape), and landscape composition surrounding grassland patches (land cover within 400 and 1600 m). Our results confirmed that nest predators respond to habitat at multiple scales and different predator species respond to habitat in different ways. The most informative habitat models we selected included variability in local vegetation (CV in the density of forbs), local patch (area and edge‐to‐interior ratio), and landscape within a 1600 m buffer around grasslands (percent of land covered by human structures and development). As a separate question, we asked if models that incorporated information from multiple scales simultaneously might improve the ability to explain variation in the predator community. Multi‐ scale models were not consistently superior to models derived from variables focused at a single spatial scale. Our results suggest that minimizing human development on and surrounding conservation land and the management of the vegetation structure on grassland fragments both may benefit grassland birds by decreasing the risk of nest predation.