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1.
温度对鸟类的繁殖具有重要影响,气候变化可导致鸟类生活史特征的改变。为了解气候变化对家燕(Hirundo rustica)巢利用率和窝卵数的影响,于2014—2015年4月,对海南临高4个村庄的家燕繁殖情况进行了调查。结果表明,2015年家燕种群开始繁殖的日期较2014年显著推迟,同时巢的利用率也低于2014年(!2=70.37,P0.001)。通过对两年繁殖季的气候状况进行分析,发现4月份的气温变化对家燕开始繁殖的时间具有重要影响。2015年4月份的平均最低气温比2014年低约2℃(t=3.155,df=58,P=0.003),且平均温差较大,表明2015年4月份偏低的春季温度及其较大的温度波动推迟了当地家燕种群的开始繁殖时间;但温度对家燕的窝卵数(t=0.670,df=87,P=0.505)和孵化成功率(t=0.794,df=71,P=0.442)没有显著影响。研究表明,即便在热带地区,春季低温对海南家燕种群开始繁殖的时间和巢利用率仍具有重要影响。  相似文献   

2.
新疆北部白冠攀雀的巢与巢址选择   总被引:1,自引:0,他引:1  
2008年4—7月,在新疆北部对白冠攀雀巢址选择进行了研究。白冠攀雀的营巢习性特殊,巢呈囊袋状,结构甚为精致。对于白冠攀雀巢的研究,采用总面积调查法,进行地毯式的搜寻,并结合标图法对其进行标记,绘制分布图。研究结果共发现巢125个,营巢位于于临近湖泊、河流等水域附近的柳树、杨树、桦树等阔叶树上。营巢树种以柳树为主,占68.80%。巢的高度平均为(5.3±2.5)m,营巢于乔木的中下部(约1/3处),约70%的巢离河边不足30 m。对于巢址选择的研究,将原始记录中与巢址选择有关的特征变量进行主成分分析,分析表明,影响白冠攀雀巢址选择的主要因素有4种,依次为:郁闭度因素(包括营巢树胸径、巢上郁闭度)、营巢树种因素(包括营巢树种、树高、巢位高度和乔木种类)、方位因素(包括距河边距离和巢向)、食物与巢材因素。  相似文献   

3.
大杜鹃(Cuculus canorus)是一种专性巢寄生鸟类,进化出了一系列适应对策,如雏鸟普遍出壳较早等,以更好适应寄生生活。本研究使用恒温自动孵化箱对25枚大杜鹃卵和20枚其宿主东方大苇莺(Acrocephalus orientalis)卵进行人工孵化,并对孵卵期的卵重进行连续测量。结果表明,在人工孵化条件下,大杜鹃卵的孵化率(76%)极显著高于东方大苇莺(40%)(χ~2=25.144,df=1,P0.01)。尽管大杜鹃的卵鲜重(t=7.447,df=43,P0.01)和卵体积(t=8.817,df=43,P0.01)均极显著大于东方大苇莺,但两种鸟卵的孵卵期不存在显著性差异(t=1.006,df=16,P0.05)。  相似文献   

4.
2003—2006年,在北京小龙门林场共发现黄眉姬鹟(Ficedula narcissina elisae)巢43个。其中34巢筑于天然巢址:开放巢占29.4%,位于树枝间(10巢);洞巢占70.6%,位于树桩顶端凹坑中(10巢)和树洞中(14巢)。开放巢距地高度高于洞巢。黄眉姬鹟的主要营巢树种是棘皮桦(Betula dahurica)。在研究区内共悬挂了100个大洞口巢箱和130个小洞口巢箱,结果发现黄眉姬只利用大洞口巢箱(9巢),不利用小洞口巢箱。以巢为中心,取半径6m的样方测量巢址的植被特征。对海拔、坡向、林冠郁闭度、乔木数量、乔木高、乔木胸径、枯树数量、树桩数量和林下郁闭度等变量进行主成分分析。结果表明,黄眉姬鹟的巢址具有乔木高大、林冠郁闭度高、多枯树和树桩等特征。黄眉姬鹟的繁殖成功率为51.2%,天敌破坏是造成繁殖失败的主要原因。  相似文献   

5.
2011年5~7月对甘肃安西极旱荒漠国家级自然保护区(N40°21'~40°22',E96°13'~96°14',海拔1 306 m)荒漠伯劳(Lanius isabellinus)巢址选择和繁殖成功进行研究。调查了58巢的巢址因子,巢主要位于营巢树主枝上,巢距地面高度多为2.0~2.5 m。主成分分析结果表明,巢距地面高度、营巢树高度、营巢树胸径和营巢处树干直径是影响荒漠伯劳巢址选择的主要因素,这也是荒漠伯劳适应繁殖地大风天气的结果。既调查巢址数据又明确繁殖情况的49个巢中,红柳(Tamarix ramosissima)(5棵)上巢的繁殖成功率明显高于沙枣(Elaeagnus angusifolia)(43棵)和胡杨(Populus euphratica)(1棵)上的巢,原因可能是红柳郁闭度大。已知窝卵数和繁殖情况的30个巢中,窝卵数分别为2(1巢)、4(7巢)、5(18巢)、6(4巢)。卡方检验结果表明,窝卵数和繁殖成功率之间差异不显著(χ2=3.921,df=3,P0.05)。发现的63个巢中跟踪监测了54个巢(包括调查巢址数据的和未调查巢址数据的)的繁殖情况,54巢中37巢繁殖成功,成功率为68.52%。所有繁殖失败的巢均为产卵阶段或育雏早期阶段由于同类的破坏而导致繁殖失败,繁殖失败巢的数量随着相邻最近巢的距离的增加而减少,因而,繁殖失败可能与种群密度以及种内竞争有关。  相似文献   

6.
2016和2017年的5月至8月,在河南省董寨国家级自然保护区利用红外相机监控和野外直接观察赤腹鹰(Accipiter soloensis),对其孵卵节律和巢防卫行为进行了研究。为了更好地获得巢防卫数据,我们以人作为入侵者攀爬巢树,观察人停留在巢树上10 min内不同赤腹鹰个体的巢防卫行为。共发现赤腹鹰繁殖巢52个,累计拍摄红外照片661 306张,将15个繁殖巢内的30只个体的巢防卫行为分成了4个等级。研究表明:1)雄鸟的巢防卫等级与雄鸟的日孵卵次数(r=0.751,n=15,P0.01)、雄鸟日孵卵时间(r=0.803,n=15,P0.01)、每日雌雄孵卵总时间(r=0.527,n=15,P0.05)均呈显著正相关,雌鸟的巢防卫等级与雄鸟的日孵卵次数(r=0.717,n=15,P0.01)、雄鸟的日孵卵时间(r=0.619,n=15,P0.05)呈显著正相关(Sperman rank correlation);2)雌鸟巢防卫强度与雄鸟巢防卫强度呈显著正相关(r=0.743,n=15,P0.01);3)亲鸟的平均离巢时间与雄鸟的日孵卵次数(r=﹣0.680,df=11,P0.05)、雄鸟的日孵卵时间(r=﹣0.640,df=11,P0.05)、雌鸟的孵卵次数(r=﹣0.558,df=11,P0.05)、每日雌雄孵卵总时间(r=﹣0.772,df=11,P0.01)均呈负相关。可见,赤腹鹰的巢防卫强度和孵卵投入密切相关,并且配偶间的巢防卫行为存在相似性,可能与配偶选择和学习行为有关。  相似文献   

7.
芜湖市及附近地区三种鹭鸟巢址特征   总被引:2,自引:0,他引:2  
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.  相似文献   

8.
巢捕食是影响鸟类繁殖成功率的一个重要因素,也是鸟类繁殖生态研究中的一项重要内容。确定鸟类的主要巢捕食者及影响巢捕食的因素对于了解鸟类繁殖成功率、种群增长率及种群数量等具有重要意义。2009—2012年,对辽宁仙人洞国家级自然保护区人工巢箱中繁殖的杂色山雀(Parus varius)、沼泽山雀(P.palustris)、大山雀(P.major)和白眉姬鹟(Ficedula zanthopygia)四种鸟类的巢捕食率及影响巢捕食的因素进行了研究。研究共记录到238个繁殖巢(杂色山雀74巢、沼泽山雀21巢、大山雀118巢、白眉姬鹟25巢),其中35巢被捕食,捕食率为14.7%,雏鸟期被捕食占91.4%。巢捕食率在4种鸟类之间无差异(x~2=0.429,df=3,P=0.934)。以锦蛇(Elaphe spp.)为代表的蛇类是该地区小型森林洞巣鸟类繁殖期主要捕食者,占总捕食率的94.3%。对影响巢捕食的22个相关因子进行二元逻辑斯蒂回归分析发现,坡度、地面裸露率、草本盖度对巢捕食具有显著性影响;出雏时间、坡位、距碎石块距离对巢捕食的影响接近显著水平;而巢高、树粗、巢箱年龄、窝卵数、距路距离等对巢捕食无显著影响。因此,处于坡度较陡,坡位较高,草本覆盖率较高,地面裸露率较低,距碎石块距离较近,且出雏时间较晚的巢更容易被捕食。  相似文献   

9.
通采用人工调查, 测量的方法, 记录了董寨自然保护区内2016—2019年共计49个朱鹮巢穴各项数据, 通过分析获得朱鹮巢穴所在位置的气象因子、海拔、郁闭度、巢-觅距、干扰因素等因素与朱鹮窝卵数和繁殖成功率相互关系。结果表明: 董寨自然保护区自2016年野化放飞朱鹮到2019年止, 野外巢穴数量逐渐增加, 营巢区域不断扩大, 但营巢地点相对集中; 朱鹮选择筑巢树种多为马尾松, 选择频次显著高于黄山松(P < 0.05)。气象因子(温度和降水量)、朱鹮营巢地海拔、筑巢树种、营巢地林间郁闭度、巢—觅距及人为干扰因素并不影响朱鹮的窝卵数, 但营巢地海拔(P < 0.001)、巢—觅距(P = 0.001)显著影响朱鹮的繁殖成功率, 营巢地海拔越高, 巢—觅距越短, 朱鹮的繁殖成功率越高; 干扰因素中人为干扰对朱鹮繁殖成功率的影响比种间竞争和天敌大, 人为干扰强度越大, 朱鹮的繁殖成功率越低。朱鹮繁殖影响因子的研究为提高董寨自然保护区朱鹮野外繁殖成功率, 当地保护部门更好的保护野外朱鹮提供科学依据。  相似文献   

10.
北红尾鸲(Phoenicurus auroreus)是一种分布广泛的小型雀形目鸟类,主要分布于南亚东北部,东南亚北部、东亚及俄罗斯等地区,我国东北、华北、华中至西南等地也均有分布,是重要的食虫益鸟。为探究北红尾鸲巢址选择的影响因素,找到影响北红尾鸲繁殖成功率的主要巢址因子,于2017年4—7月,在辽宁仙人洞国家级自然保护区开展系统研究。共发现北红尾鸲自然巢44个,其中29巢繁殖成功,15巢繁殖失败。北红尾鸲主要筑巢于石墙缝、空心砖墙缝及废旧电表箱中。巢址参数的主成分分析结果表明:巢口因子(27.738%)、巢位因子(14.195%)、光照因子(12.145%)、人为干扰因子(10.440%)、安全因子(9.266%)和隐蔽因子(7.187%)是影响北红尾鸲巢址选择的重要因子。采用二元逻辑斯蒂回归分析繁殖成功巢与失败巢参数发现,成功巢的巢口最大高度显著小于失败巢(P=0.047),且其距顶的距离更近(P=0.043)。多元线性回归分析表明,巢上方盖度对繁殖成功率有极显著影响(t=2.883,P=0.009)。总的来说,北红尾鸲虽偏爱筑巢于人为干扰较大的村庄房屋附近,但较小的巢口能有效避免巢捕食者的捕食,更近的距顶距离和更大的巢上方盖度能有效降低巢上方的可视程度和降水等不利因素的影响,从而提高繁殖成功率。  相似文献   

11.
Mistletoes are preferred nesting sites for many bird species in a range of habitats. However, no studies have examined the use of mistletoes by nesting birds in the semi‐arid savannah. We studied nesting in mistletoe and its role in determining nesting success in the Grey Go‐away‐bird in south‐west Zimbabwe. We modelled the effects of mistletoe, mistletoe abundance, nest microclimate, concealment and nest height on daily survival rates (DSR) using program MARK. A constant survival model was best fitted for the Grey Go‐away‐bird suggesting a constant nest survival rate across the nesting period. Mistletoe nests had lower DSR than nests placed elsewhere in the canopy. Mistletoe abundance and nest height had a positive association with DSR whereas visibility distance, microclimate and concealment were negatively associated with DSR. Overall, survival for nests in mistletoe was 22.1% compared with 90.5% for nests in other substrates over the 50‐day nesting period. In conclusion, the low nest survival in mistletoe suggests either that the factors used to select mistletoe as nest sites by these birds are poor predictors of nest success or that nesting in mistletoe may be maladaptive.  相似文献   

12.
We conducted a survey of the distribution of Ferruginous Duck Aythya nyroca across Algeria and analysed the influence of nest-site characteristics on nesting success at a Ramsar site, Lake Tonga. The species was found to occupy different wetlands (freshwater lakes, brackish marshes and salt lakes) across three major climatic belts (subhumid coastal strip, semi-arid Hauts Plateaux and arid Sahara). Mean clutch size of successful nests was 13.3 ± 6.0 eggs (N = 26) with a hatching rate of 74% for successful clutches. Nesting success was recorded for 44% of nests with clutch desertion (72.7%) accounting for the majority of failed clutches. Egg size of the study population, which breeds at the southern limit of the species’ range, was significantly smaller than that of its northerly counterparts. Clutch size was negatively related to egg size and positively associated with depth of water below the nest, suggesting that older, more experienced or high-quality birds monopolised the safest sites. Successful clutches were significantly associated with tall vegetation, suggesting that when nesting is carried out mainly on offshore floating islets, protection against aerial predators and heat stress determine nesting outcome. Conspecific brood parasitism was significantly and positively associated with deferred egg-laying and smaller egg size, suggesting an age-dependent mechanism.  相似文献   

13.
Grassland birds have experienced steeper population declines between 1966 and 2015 than any other bird group on the North American continent, and migratory grassland birds may face threats in all stages of their annual cycle. The grassland-associated long-billed curlew (Numenius americanus) is experiencing population declines in regional and local portions of their North American breeding range. The nesting period is an important portion of the annual cycle when curlews may face demographic rate limitations from a suite of threats including predators and anthropogenic disturbance. We compared nest sites to random sites within breeding territories to examine nest site selection, and modeled correlates of nesting success for 128 curlew nests at 5 Intermountain West sites. Nest sites were 6 times more likely than random sites to be situated adjacent to existing cowpies. Additionally, curlews selected nest sites with shorter vegetation, and less bare ground, grass, and shrub cover than at random sites within their territories. Nest success varied widely among sites and ranged from 12% to 40% in a season with a mean of 27% for all nests during the 2015 and 2016 seasons. Higher nest success probability was associated with higher curlew densities in the area, greater percent cover of conspicuous objects (cowpies, rocks) near the nest, and higher densities of black-billed magpies (Pica hudsonia) and American crows (Corvus brachyrhynchos) at the site. We also found increased probability of nesting success with increased distance from a nest to the nearest potential perch in that territory. Given the central role of working lands to curlews in much of the Intermountain West, understanding limitations to nesting success in these diverse landscapes is necessary to guide adaptive management strategies in increasingly human-modified habitats. We suggest some grazing and irrigation practices already provide suitable nesting conditions for curlews, and others may require only minor temporal shifts to improve compatibility. © 2019 The Wildlife Society.  相似文献   

14.
Abstract: The structure of vegetation in grassland systems, unlike that in forest systems, varies dramatically among years on the same sites, and among regions with similar vegetation. The role of this variation in vegetation structure on bird density and nesting success of grassland birds is poorly understood, primarily because few studies have included sufficiently large temporal and spatial scales to capture the variation in vegetation structure, bird density, or nesting success. To date, no large-scale study on grassland birds has been conducted to investigate whether grassland bird density and nesting success respond similarly to changes in vegetation structure. However, reliable management recommendations require investigations into the distribution and nesting success of grassland birds over larger temporal and spatial scales. In addition, studies need to examine whether bird density and nesting success respond similarly to changing environmental conditions. We investigated the effect of vegetation structure on the density and nesting success of 3 grassland-nesting birds: clay-colored sparrow (Spizella pallida), Savannah sparrow (Passerculus sandwichensis), and bobolink (Dolichonyx oryzivorus) in 3 regions of the northern tallgrass prairie in 1998–2001. Few vegetation features influenced the densities of our study species, and each species responded differently to those vegetation variables. We could identify only 1 variable that clearly influenced nesting success of 1 species: clay-colored sparrow nesting success increased with increasing percentage of nest cover from the surrounding vegetation. Because responses of avian density and nesting success to vegetation measures varied among regions, years, and species, land managers at all times need to provide grasslands with different types of vegetation structure. Management guidelines developed from small-scale, short-term studies may lead to misrepresentations of the needs of grassland-nesting birds.  相似文献   

15.
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.  相似文献   

16.
The habitat selection choices that individuals make in response to thermal environments influence both survival and reproduction. Importantly, the way that organisms behaviorally respond to thermal environments depends on the availability and juxtaposition of sites affording tolerable or preferred microclimates. Although, ground nesting birds are especially susceptible to heat extremes across many reproductive stages (i.e., breeding, nesting, brood rearing), the mechanistic drivers of nest site selection for these species are not well established from a thermal perspective. Our goal was to assess nest site selection relative to the configuration of the thermal landscape by quantifying thermal environments available to a ground-nesting bird species inhabiting a climatically stressful environment. Using northern bobwhite (Colinus virginanus) as a model species, we measured black bulb temperature (Tbb) and vegetation parameters at 87 nests, 87 paired sites and 205 random landscape sites in Western Oklahoma during spring and summer 2013 and 2014. We found that thermal space within the study area exhibited differences in Tbb of up to 40°C during peak diurnal heating, resulting in a diverse thermal landscape available to ground-nesting birds. Within this thermally heterogeneous landscape, nest sites moderated Tbb by more than 12°C compared to random landscape sites. Furthermore, successful nests remained on average 6°C cooler than unsuccessful nests on days experiencing ambient temperatures ≥ 39°C. Models of future Tbb associated with 2080 climate change projections indicate that nesting bobwhites will face substantially greater Tbb throughout the landscape for longer durations, placing an even greater importance on thermal choices for nest sites in the future. These results highlight the capacity of landscape features to act as moderators of thermal extremes and demonstrate how thermal complexity at organism-specific scales can dictate habitat selection.  相似文献   

17.
Snowy plover (Charadrius nivosus) populations have declined throughout their range, in part because of habitat degradation and poor nest success, making information regarding regionally specific nest site selection and spatial patterns important when considering habitat conservation and management guidelines. We determined nest site selection characteristics (n = 180) and examined spatial patterns (n = 215) of snowy plover nests in saline lakes in the Southern High Plains (SHP) of Texas. At 104 nests, we examined the influence of substrate type on nest temperatures and heat mitigation. Snowy plover nests were more likely to be found near an object, on pebble substrate, and with fewer plants than random sites. High use areas were generally located in areas with pebble substrate and on human-made or natural islands, berms, and peninsulas. Overall, nests placed on pebble substrate had lower temperatures during the day than nests placed on sand substrates. Nest placement on pebble substrate may be valuable to nesting snowy plovers, providing thermal advantages to incubating adults and depressing potentially high nest predation rates. Management guidelines for this region should emphasize the importance of addressing key elements of snowy plover nesting habitat including the presence of pebble substrate and reducing vegetation encroachment. © 2012 The Wildlife Society.  相似文献   

18.
Abstract: We studied breeding dark-eyed juncos (Junco hyemalis), yellow-rumped warblers (Dendroica coronata), and spruce-nesting birds from 1997 to 1998 among forests with different levels of spruce (Picea spp.) mortality following an outbreak of spruce beetles (Dendroctonus rufipennis) in Alaska, USA. We identified species using live and beetle-killed spruce for nest sites and monitored nests to determine how the outbreak influenced avian habitat selection and reproduction. We tested predictions that 1) nesting success of ground-nesting juncos would increase with spruce mortality due to proliferation of understory vegetation available to conceal nests from predators, 2) nesting success of canopy-nesting warblers would decrease with spruce mortality due to fewer live spruce in which to conceal nests, and 3) both species would alter nest-site selection in response to disturbance. Juncos did not benefit from changes in understory vegetation; nesting success in highly disturbed stands (46%) was comparable to that in undisturbed habitats throughout their range. In stands with low spruce mortality, nesting success of juncos was low (5%) and corresponded with high densities of red squirrels (Tamiasciurus hudsonicus). Yellow-rumped warblers nested exclusively in spruce, but success did not vary with spruce mortality. As disturbance increased, nesting warblers switched from selecting forest patches with high densities of live white spruce (Picea glauca) to patches with beetle-killed spruce. Warblers also placed nests in large-diameter live or beetle-killed spruce, depending on which was more abundant in the stand, with no differences in nesting success. Five of the 12 other species of spruce-nesting birds also used beetle-killed spruce as nest sites. Because beetle-killed spruce can remain standing for >50 years, even highly disturbed stands provide an important breeding resource for boreal forest birds. We recommend that boreal forest managers preserve uncut blocks of infested forest within managed forest landscapes and practice partial harvest of beetle-killed spruce rather than commercial clear-cutting of infested stands in order to sustain breeding bird populations until natural reforestation occurs. Because breeding densities do not always reflect fitness, assessing impacts of a massive natural disturbance should include measuring impacts of changes in vegetation on both reproductive success and predator-prey dynamics.  相似文献   

19.
Predation is the main cause of passerine nesting failure. Traditionally, large intraspecific group size is thought to accrue individuals with fitness benefits from increased predator vigilance and hence lower predation risk. To date, few studies have investigated interspecific group size in relation to predation risk. In the present study, we examined predation outcome in Darwin's small tree finch, Camarhynchus parvulus , in nests with many or few interspecific neighbours. We tested the predictions: (1) nests in mixed associations have lower predation than do more solitary nests; (2) mixed species nesting associations covary with nest site vegetation characteristics; (3) older (i.e. presumably experienced) males more commonly nest in mixed associations than younger males; (4) older males select more concealed nesting sites; and (5) controlling male age, females prefer to pair with males in mixed associations than at solitary nests. Almost half of all nests occurred in mixed associations (46%) compared to solitary nests (54%), and the overall distribution of nests was decidedly nonrandom, displaying a bimodal pattern. Nest site vegetation characteristics of the focal species were inconsistently associated with nesting pattern, but older males did select more concealed nesting sites. Controlling differences in surrounding vegetation characteristics, mixed nesting associations experienced markedly lower predation than solitary nests, and females showed a preference for males in mixed associations, as demonstrated by higher male pairing success.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 98 , 313–324.  相似文献   

20.
Although avian nesting success is much studied, little is known about the relative importance of the factors that contribute to annual reproductive success and population limitation, especially for long‐distance migratory songbird species. We combined a field experiment limiting access to nests by mammalian predators with modeling of long‐term field data of American redstarts (Parulidae: Setophaga ruticilla) to assess the effects of multiple environmental variables on breeding success and population limitation. Experimental treatment (baffles placed around tree boles beneath active nests; n = 71) increased nesting success of this single‐brooded species significantly (77 vs 50% in controls; n = 343), demonstrating that scansorial mammals, primarily red squirrels Tamiasciurus hudsonicus and eastern chipmunks Tamias striatus, reduced reproductive success. Based on unbaffled nests (n = 466), daily nest survival varied annually, and was positively influenced by May temperature and negatively by sciurid nest predator abundance. Daily nest survival was also influenced positively by June rainfall, and declined with nest age but not with calendar date. Since nest failure was overwhelmingly caused by nest predation, these significant climate and nest‐age effects in our models are indirect, likely influencing nest predator and/or nesting bird behaviors that in turn influenced nest predation. Redstart population density had no effect on nesting success, after accounting for other factors. Annual reproductive success accounted for 34% of the variability in annual population change in redstarts in our study area. Our findings document 1) breeding season population limitation in this species, 2) a link between tree masting and bird population dynamics via mammal population fluctuations, 3) the independent contributions of summer versus winter population processes in a migratory species, and 4) the potential complexity of climate‐biotic interactions.  相似文献   

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