青海北部高寒草甸雀形目鸟类繁殖生态学的研究进展

从鸟巢特征、巢址选择、窝卵数、育幼行为、雏鸟生长发育、繁殖生产力以及繁殖对策等方面,对青藏高原高寒草甸雀形目鸟类繁殖生态学进行了综合分析与评述。高寒草甸雀形目鸟类受适合繁殖季节长度、食物资源和捕食压力的影响,或选择逐步投资对策,或选择一次投资对策;每个种群的常见窝卵数就是最适窝卵数;雏鸟的发育模式相对固定,不存在补偿性生长,但是生长期长度是可变化的。①研究亲-子通讯行为的进化和稳定性,提出适应高寒草甸雀形目鸟类的亲-子间的通讯行为假设;②建立在巢环境特征变化梯度(开放到封闭)上的生命表,找出决定适合度的生命表参数(繁殖率和存活率)的因果关系;③测定在巢环境特征变化梯度上的生态领域变化将是未来研究的3个方向。     

两种雀形目鸟类孵化行为对子代质量的影响

对高寒草甸地面营巢的小云雀 (Alaudagulgula)和灌丛筑巢的黄嘴朱顶雀 (Acanthisflavirostris)繁殖方式的研究表明 :①小云雀孵化异步性较弱 (1d) ;平均卵重与产卵顺序不显著相关 ,但最后 1枚卵最重 ;出壳顺序与雏鸟生长率极显著正相关 (P <0 0 1) ;出壳顺序对幼鸟的雏期和离巢体重无显著影响 (P >0 0 5 )。②黄嘴朱顶雀孵化异步性较强 (2～ 3d) ;平均卵重与产卵顺序显著正相关 (P <0 0 5 ) ,最后 1枚卵最重 ,第 1枚次之 ;出壳顺序对雏鸟生长率、雏期和离巢体重均无显著影响 (P >0 0 5 )。结果分析表明 ,2种雀形目鸟类都选择了异步孵化和加强窝雏数对策的繁殖模式。     

吉林白城地区草原栗斑腹(巫鸟)窝卵数、营巢成功率和繁殖成功率的研究

对分布于吉林白城地区草原生境中栗斑腹巫鸟的窝卵数、营巢成功率和繁殖成功率的初步研究结果表明 ,繁殖期栗斑腹巫鸟种群的平均窝卵数为 5 .0 9± 0 .5 8枚 /巢 ;窝卵数与产卵期、出巢数与产卵期、窝卵数与卵大小之间呈负相关 ,产卵期与孵化率之间存在极显著的负相关关系 ,巢外径与窝卵数之间存在显著的正相关关系 ,巢的其余指标均与窝卵数呈正相关 ;平均孵化期为 12± 0 .4 9d ,孵化率为 36 .3% ,繁殖成功率为 11.11% ;7日龄以上的雏鸟群体大小为 2 .5 6± 1.5 3只 ,栗斑腹巫鸟的雏鸟存活率为 2 7.6 9% .     

营巢植物影响红头长尾山雀的巢被捕食风险

巢址选择对鸟类的巢捕食率具有重要影响,研究鸟类的巢址特征与巢捕食率之间的关系有利于揭示不同巢址特征对鸟类成功繁殖的作用。本研究以2014至2017年在河南董寨国家级自然保护区观察的红头长尾山雀(Aegithalos concinnus)为研究对象,分析了红头长尾山雀在卵期(产卵及孵卵期)(n = 124巢)及育雏期(n = 119巢)被捕食巢和成功巢的日存活率与发现巢的时间和营巢植物种类之间的关系,同时还根据其巢址的总体特征对其巢址安全性进行评级,以探究研究者评估的巢址安全等级对预测巢存活率的有效性。结果显示：在卵期,营巢于竹类植物(如箬竹Indocalamus tessellatus和刚竹属Phyllostachys sp.植物)、茶(Camellia sinensis)、灌草类植物(如蔷薇Rosa spp.和禾本科Gramineae植物)和杉木(Cunninghamia lanceolata)上的红头长尾山雀巢的日存活率皆显著高于在松柏类植物(如油松Pinus massoniana、侧柏Platycladus orientalis和圆柏Juniperus chinensis)上的巢;在育雏期,营巢于灌草类植物上巢的日存活率显著低于竹类、杉木和茶树上巢的日存活率。卵期巢的日存活率随巢日龄的增加而显著降低,但育雏期巢的日存活率不随巢日龄显著变化。此外,巢的日存活率与发现巢的日期之间没有显著关系,研究者评估为巢址安全等级不同的巢,其日存活率也无显著差异。综上所述,本研究的结果表明,营巢于某些特定植物有助于降低红头长尾山雀面临的巢捕食风险,说明营巢植物种类对鸟类的繁殖成功率具有重要影响。     

基于人工巢试验分析黄腹角雉巢卵捕食者

2007年至今,我国在陕西宁陕、铜川和千阳,以及河南董寨和浙江德清初步建立了朱鹮(Nipponia nippon)野化放归种群。鸟类的繁殖行为是其生活史策略的重要组成部分,可以反映动物个体的营养状态、所处栖息地的质量,以及对栖息地的适应等。本文报道浙江德清朱鹮野化放归种群的繁殖行为,旨在了解其在我国南方的适应情况,为最终建立中国朱鹮南方种群提供科学支撑。本研究于2018年4和5月及2020年3至5月对浙江德清野化放归朱鹮的3个繁殖巢进行实时监测,记录孵卵期和育雏期繁殖行为,总记录时长为134 d,有效数据时长为2 958 h。利用线性混合模型探究朱鹮衔巢材频率、孵卵期以及育雏期行为的影响因子,采用Spearman相关分析检验朱鹮翻卵频率与孵卵进程的关系,建立Logistic回归模型探究朱鹮亲鸟暖雏时长随雏鸟日龄的变化情况,并利用one-way ANOVA分析德清朱鹮与陕西洋县野生种群和其他野化放归种群的换巢频率差异。结果表明,德清朱鹮平均窝卵数3.7 ± 0.3,孵化成功率90.9%,雏鸟出飞率100.0%;繁殖的不同时期、营巢条件和亲鸟性别均显著影响朱鹮的衔巢材频率;朱鹮的翻卵频率随孵卵进程显著下降;亲鸟的暖雏时长在雏鸟11日龄时下降率最大;育雏的不同时期对朱鹮的暖雏时长、换巢频率以及喂雏频率有极显著的影响;环境温度较高可能是导致德清朱鹮比洋县野生种群提前产卵的原因之一;较高的平均窝卵数与出飞成功率表明,朱鹮对我国南方的栖息地较为适应。鉴于本研究发现利用人工巢筐营巢的亲鸟花费更多时间补充巢材,表明人工巢筐的结构和大小有必要优化,建议在今后设计时加大筐壁仰角并减小深度、扩大外径,使人工巢筐更接近于自然巢的盘状结构,同时,应将巢筐底部设计成多孔透气、利于排水的结构,以适应我国长江中下游地区湿热多雨的气候。     

人工巢箱繁殖鸟类主要巢捕食者及其影响因素

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。     

模拟增加潜在巢捕食风险对2种鸟类雏鸟生长发育产生不同影响

捕食风险是影响鸟类生活史对策的重要因素之一。为应对捕食风险,鸟类进化出多样的反捕食策略。为探究北热带石灰岩森林地区鸟类生长发育对高巢捕食风险的适应机制,本研究通过利用蛇类模型模拟巢捕食者,增加潜在巢捕食风险,设置实验组,将未放置蛇类模型的实验设置为对照组。测量育雏期内黄腹山鹪莺（Prinia flaviventris）雏鸟与红耳鹎（Pycnonotus jocosus）雏鸟每日的体重、跗跖长与翼长,分别比较分析黄腹山鹪莺雏鸟与红耳鹎雏鸟上述体型特征在实验组与对照组中的生长发育规律。对符合正态分布的各日龄雏鸟生长参数进行t检验,不符合正态分布的参数进行非参数检验（Wilcox秩和检验）并求均值,使用SPSS 26.0统计软件包对雏鸟各日龄参数均值进行Logistic曲线拟合,比较各雏鸟相同生长参数在实验组和对照组实验的“S”发育曲线。结果显示,黄腹山鹪莺雏鸟在实验组的体重、跗跖长与翼长的渐近线分别占成鸟量度的71.57%、94.10%与55.29%,对照组分别占成鸟量度的78.05%、97.49%与55.67%,在实验组和对照组育雏期分别为11.1 d与10.6 d。实验组和对照组黄腹山...     

虎纹伯劳的巢生境选择与繁殖行为

2005年3~7月通过焦点动物取样法(focal animal sampling)和完全记录法(all-occur rencerecording)对四川南充地区虎纹伯劳的繁殖行为进行了研究。结果表明,虎纹伯劳喜在5~12m的高大阔叶乔木的冠部分叉处营巢。对15个巢址主成分分析表明,前5个主成分特征值均大于1,累积贡献率高达83.15%,说明前5个主成分已经基本包含了所有参数的总信息量。4月下旬开始陆续有虎纹伯劳迁到,初到时并未配对。5月上旬开始出现求偶行为,并伴有递食行为。5月中旬首次见到营巢,两性参与营巢,营巢期5~7d。营巢结束一两天后开始产卵,一天一枚,窝卵数4~6枚。营巢期和产卵期都有求偶和交配行为。产完最后1枚卵后即开始由雌鸟单独孵卵,孵卵期13~14d。两性育雏,育雏期13~15d。     

新疆木垒波斑鸨营巢成功率的初步研究

1998年 4月中旬～ 7月中旬 ,对分布于新疆木垒的波斑鸨 (Chlamydotisundulatamacqueenii)种群的营巢成功率进行了初步考察与研究。考察中共发现 16个巢、2 5窝幼雏。每巢产卵 3～ 6枚 ,卵鲜重 (6 4 7± 5 8)g ,卵径为 6 0 9mm× 43 9mm。产卵有两个高峰期 ,表明雌鸟第 1次繁殖失败后可再次产卵。第 1产卵期的巢卵数为(4 1± 0 8)枚 ,第 2产卵期的巢卵数为 (3 5± 0 6 )枚。雌鸟营巢成功率为 77 5 %～ 87 5 % ,卵的孵化率为83 6 %。每窝内从破壳到具备飞行能力的幼雏数基本不变 ,表明繁殖雌鸟大都能将幼雏全部抚育到可以飞行的年龄     

欧夜鹰的繁殖生态与移巢行为

2008年6至8月及2018年6月和7月,采用实地观察、测量和红外相机监测方法对新疆乌鲁木齐郊外头屯河流域欧夜鹰（Caprimulgus europaeus）的栖息环境、巢间距、窝卵数、孵卵、育雏、幼鸟生长及移巢行为进行了调查和分析。利用红外相机监测3个巢,监测时间分别为 15 d、23 d和11 d,共拍摄照片8 462 张,视频4 152个片段,约40 h,经过筛选得到有效照片6 807张。结果表明,欧夜鹰的巢均置于河道中央的河心岛及乱石滩沙地上,周围植被稀疏。两巢间距最近为69 m,巢密度3 ~ 7个/km2。每窝产卵2枚（n = 7）,卵长径为（30.53 ± 0.88）mm,卵短径为（21.39 ± 0.85）mm,卵体积为（7.13 ± 0.50）cm3,卵重为（7.27 ± 0.38）g（n = 5）。孵卵期为15或16 d,孵卵期成鸟离巢觅食呈双峰型,分别在天黑后的20:00 ~ 21:00时和黎明前的03:00 ~ 04:00时。育雏期为16 ~ 18 d,育雏期和孵卵期成鸟活动强度存在明显的差异,成鸟喂食幼鸟亦呈双峰型,分别在夜里的20:30 ~ 22:30时和黎明前的02:30 ~ 04:30时。成鸟的行为谱可分为9类46种,幼鸟的行为谱可分为6类32种。雏鸟的体重、体长、翅长生长发育遵循Logistic方程规律,呈曲线变化,尾长、跗跖长和嘴峰长则遵循线性生长规律。欧夜鹰的移巢行为十分独特：一是为了躲避日晒,以避免幼鸟被阳光灼伤;二是避开干扰（天敌、牧群、洪水及人类活动等）。     

Competition, predation and nest niche shifts among tropical cavity nesters: phylogeny and natural history evolution of parrots (Psittaciformes) and trogons (Trogoniformes)

Nest site selection by birds is a critically important life history trait as competition for suitable sites can be intense, and because birds are at their most vulnerable to predators during nesting. Previous studies show that the clutch size and nestling period evolve in response to competition for nest sites and nest predation, respectively. This provides the opportunity to study the relative contribution of competition and predation to the evolution of nesting niche. Using previously published phylogenies for parrots and trogons, I found evidence for at least 13 independent evolutionary transitions from tree cavities to alternative nesting niches (including termitaria, cliffs, and burrows). I analyzed variations in clutch size, incubation period and nestling period for 16 phylogenetically controlled pairs of species to test the relative roles of competition for tree cavities and nest predation, in favoring evolutionary switches to alternative nest sites. Tree cavity nesting species did not have larger clutch sizes as predicted if competition for tree cavities leads birds to invest heavily in nesting once they obtain a nest site (the limited breeding opportunities hypothesis). Instead I found that shifts to alternative nesting niches were accompanied by an increase in nestling period. As nestling period is a surrogate measure for long-term nest predation rates, this finding suggests that nest predation has been more important than competition in niche diversification among cavity nesting parrots and trogons. The timing of events in South America suggests that the explosive radiation of mammalian nest predators during the Upper-Oligocene, Lower-Miocene (20–30 million years ago) corresponded with the radiation of parrot and trogon taxa that exploit novel nesting niches.     

Body mass changes in female tawny pipits Anthus campestris during the nesting stage

We analysed female body mass change, corrected by tarsus length (body condition) in tawny pipits Anthus campestris during the nesting period in a population subject to high nest predation rates (between 70 and 85%), which leads to the need for replacement clutches. Decrease in female body condition over the nesting stage (6.8 g, around 27% of the initial mass during the whole nesting process) was related to laying date, clutch size and nesting period (incubation and nestling phases). Data from recaptured females indicated a decrease during each of the three nesting phases considered (the last days of incubation and first and last days of the nestling phase), with body mass always being higher in the first of the two measurements taken in each of these phases. The observation of a continuous decrease in body condition during the last days of incubation and first and last days of the nestling phase does not support the programmed anorexia hypothesis, but adjusts well to predictions of the stress hypothesis. These results suggest that the costs accumulated during the entire nesting stage in ground passerines subjected to high nest predation rates are linked to a superimposed effect of the cost of replacement clutches.     

Age and clutch size variation in Dusky Flycatcher nest survival

Examination of spatial and temporal factors that influence nest survival can provide insight into habitat selection, reproductive decisions (e.g., clutch size), population dynamics, and conservation requirements for species. We used nest survival data for the Dusky Flycatcher Empidonax oberholseri to examine several factors that may influence nesting success. Our prediction was that the number of nest initiations would be positively associated with period nest survival. We used a model selection framework and found that nesting success was a function of clutch size and a cubic effect of age. Clutches with one, two, three, and four eggs had period survival rates of 0, 0.05, 0.33, and 0.49, respectively. Daily survival rates decreased from the onset of egg-laying and increased during the later stages of incubation before remaining relatively constant through the later portions of the nestling stage. Model-selection criterion provided support for a date effect on daily survival (i.e., daily nest survival declined across the nesting season) although the 95% confidence interval for the estimate included zero. We found that the majority of nest initiations occurred early in the nest season and declined across the season as period nest survival declined. Our prediction concerning nest survival was partially supported. In addition, we found substantial positive associations between clutch size and nest survival. While low daily survival rates for clutches with one or two eggs suggested that individuals may have reduced reproductive effort in response to nest predation risk, we did not find strong evidence that individuals reduced their clutch sizes in subsequent nest attempts. Alternative predictions, including the preferential settlement of higher quality individuals (e.g., those with the ability to lay full clutches to replace depredated nests) into high-quality habitat and differences in behavior patterns (e.g., number of visits to provision nestlings), may provide more consistent explanations for these patterns.     

Nest predation increases with parental activity: separating nest site and parental activity effects.

Alexander Skutch hypothesized that increased parental activity can increase the risk of nest predation. We tested this hypothesis using ten open-nesting bird species in Arizona, USA. Parental activity was greater during the nestling than incubation stage because parents visited the nest frequently to feed their young during the nestling stage. However, nest predation did not generally increase with parental activity between nesting stages across the ten study species. Previous investigators have found similar results. We tested whether nest site effects might yield higher predation during incubation because the most obvious sites are depredated most rapidly. We conducted experiments using nest sites from the previous year to remove parental activity. Our results showed that nest sites have highly repeatable effects on nest predation risk; poor nest sites incurred rapid predation and caused predation rates to be greater during the incubation than nestling stage. This pattern also was exhibited in a bird species with similar (i.e. controlled) parental activity between nesting stages. Once nest site effects are taken into account, nest predation shows a strong proximate increase with parental activity during the nestling stage within and across species. Parental activity and nest sites exert antagonistic influences on current estimates of nest predation between nesting stages and both must be considered in order to understand current patterns of nest predation, which is an important source of natural selection.     

Habitat-specific clutch size and cost of incubation in eiders reconsidered

The energetic incubation constraint hypothesis (EICH) for clutch size states that birds breeding in poor habitat may free up resources for future reproduction by laying a smaller clutch. The eider (Somateria mollissima) is considered a candidate for supporting this hypothesis. Clutch size is smaller in exposed nests, presumably because of faster heat loss and higher incubation cost, and, hence, smaller optimal clutch size. However, an alternative explanation is partial predation: the first egg(s) are left unattended and vulnerable to predation, which may disproportionately affect exposed nests, so clutch size may be underestimated. We experimentally investigated whether predation on first-laid eggs in eiders depends on nest cover. We then re-evaluated how nesting habitat affects clutch size and incubation costs based on long-term data, accounting for confounding effects between habitat and individual quality. We also experimentally assessed adult survival costs of nesting in sheltered nests. The risk of egg predation in experimental nests decreased with cover. Confounding between individual and habitat quality is unlikely, as clutch size was also smaller in open nests within individuals, and early and late breeders had similar nest cover characteristics. A trade-off between clutch and female safety may explain nest cover variation, as the risk of female capture by us, mimicking predation on adults, increased with nest cover. Nest habitat had no effect on female hatching weight or weight loss, while lower temperature during incubation had an unanticipated positive relationship with hatching weight. There were no indications of elevated costs of incubating larger clutches, while clutch size and colony size were positively correlated, a pattern not predicted by the ‘energetic incubation constraint’ hypothesis. Differential partial clutch predation thus offers the more parsimonious explanation for clutch size variation among habitats in eiders, highlighting the need for caution when analysing fecundity and associated life-history parameters when habitat-specific rates of clutch predation occur.     

Nest predators and the evolution of avian reproductive strategies: a comparison of Australian and New Zealand birds

Summary Nest predation has been considered an important factor in the evolution of avian life histories: smaller clutches and shorter incubation and nestling periods are expected where nest predation has significant effects on reproductive success. Unlike the Australian avifauna, terrestrial New Zealand birds have evolved in the absence of reptilian and mammalian predators. Here we compare the reproductive strategies of terrestrial native New Zealand birds with those of their Australian sister taxa. In 11 of 14 comparisons, New Zealand birds were larger than their Australian relatives, but we did not find any significant differences in reproductive tactics between the two regions, a result inconsistent with the nest predation hypothesis. We discuss several reasons why this may be so. One possibility is that selection imposed on avian life history tactics by mammalian predators following the arrival of humans in New Zealand has led to strategies similar to those adopted in Australia.     

Experiments on clutch size and nest size in passerine birds

Summary Results of experiments on three passerine species suggest that brood size may be constrained by nest size, since the breeding success of pairs provided with large nestcups was greater than that of those provided with small artificial nestcups. These results may have important implications, e.g. to the design of experiments involving manipulation of clutch and brood size. A small nestcup is requisite for successful hatching during the incubation period, but a large one for successful rearing during the nestling period. In nature this difference may select for types of nesting materials that are elastic, such as mosses and lichens. However, experiments showed that such materials rapidly absorb rainwater but only slowly dry out. In addition, because large nests dry out more slowly than small nests, selection will favour small nests among those open-nesting species that have exposed nests. A further possible nest size constraint on open-nesters is nest predation. However, no difference in the predation rate was found in experiments with small and large artificial nests.     

Temporal and Individual Variation in Offspring Provisioning by Tree Swallows: A New Method of Automated Nest Attendance Monitoring

Studies of the ecology and evolution of avian nesting behavior have been limited by the difficulty and expense of sampling nest attendance behavior across entire days or throughout a substantial portion of the nestling period. Direct observation of nesting birds using human observers and most automated devices requires sub-sampling of the nestling period, which does not allow for the quantification of the duration of chick-feeding by parents within a day, and may also inadequately capture temporal variation in the rate at which chicks are fed. Here I describe an inexpensive device, the Automated Perch Recorder (APR) system, which collects accurate, long-term data on hourly rates of nest visitation, the duration of a pair''s workday, and the total number of visits the pair makes to their nest across the entire period for which it is deployed. I also describe methods for verifying the accuracy of the system in the field, and several examples of how these data can be used to explore the causes of variation in and tradeoffs between the rate at which birds feed their chicks and the total length of time birds spend feeding chicks in a day.     

Factors Affecting the Duration of Nestling Period and Fledging Order in Tengmalm’s Owl (Aegolius funereus): Effect of Wing Length and Hatching Sequence

In altricial birds, the nestling period is an important part of the breeding phase because the juveniles may spend quite a long time in the nest, with associated high energy costs for the parents. The length of the nestling period can be variable and its duration may be influenced by both biotic and abiotic factors; however, studies of this have mostly been undertaken on passerine birds. We studied individual duration of nestling period of 98 Tengmalm’s owl chicks (Aegolius funereus) at 27 nests during five breeding seasons using a camera and chip system and radio-telemetry. We found the nestlings stayed in the nest box for 27 – 38 days from hatching (mean ± SD, 32.4 ± 2.2 days). The individual duration of nestling period was negatively related to wing length, but no formally significant effect was found for body weight, sex, prey availability and/or weather conditions. The fledging sequence of individual nestlings was primarily related to hatching order; no relationship with wing length and/or other factors was found in this case. We suggest the length of wing is the most important measure of body condition and individual quality in Tengmalm’s owl young determining the duration of the nestling period. Other differences from passerines (e.g., the lack of effect of weather or prey availability on nestling period) are considered likely to be due to different life-history traits, in particular different food habits and nesting sites and greater risk of nest predation among passerines.     

Life-history variation of a neotropical thrush challenges food limitation theory

Since David Lack first proposed that birds rear as many young as they can nourish, food limitation has been accepted as the primary explanation for variation in clutch size and other life-history traits in birds. The importance of food limitation in life-history variation, however, was recently questioned on theoretical grounds. Here, we show that clutch size differences between two populations of a neotropical thrush were contrary to expectations under Lack's food limitation hypothesis. Larger clutch sizes were found in a population with higher nestling starvation rate (i.e. greater food limitation). We experimentally equalized clutches between populations to verify this difference in food limitation. Our experiment confirmed greater food limitation in the population with larger mean clutch size. In addition, incubation bout length and nestling growth rate were also contrary to predictions of food limitation theory. Our results demonstrate the inability of food limitation to explain differences in several life-history traits: clutch size, incubation behaviour, parental feeding rate and nestling growth rate. These life-history traits were better explained by inter-population differences in nest predation rates. Food limitation may be less important to life history evolution in birds than suggested by traditional theory.