All "chick-a-dee" calls are not created equally. Part II. Mechanisms for discrimination by sympatric and allopatric chickadees

The 'chick-a-dee' call, common to all members of the genus Poecile, is used by both sexes throughout the year to putatively co-ordinate flock movements and register alarm. In some regions, two or more chickadee species occupy overlapping territories, and therefore it is essential that these sympatric species learn to discriminate between the acoustically similar calls of the species. Previous work from our laboratory has shown that black-capped (P. atricapillus) and mountain chickadees (P. gambeli) discriminate between the species' calls and treat each species' calls as belonging to separate open-ended categories. In the current set of experiments we use an operant conditioning paradigm to gain an understanding of (1) how the birds perform this discrimination and (2) whether birds with different levels of experience with heterospecific calls perform this task differently. We use natural recordings of chick-a-dee calls and perform several manipulations to test the importance of the introductory 'chick-a' portion and the terminal 'dee' portion for discriminating among the calls of the two species. Evidence suggests that birds mainly use the terminal 'dee' portion, as all groups of birds responded similarly to these probe stimuli and control chick-a-dee calls. We propose that the terminal 'dee' portion, consisting of lower frequency notes, is more likely to be resistant to degradation, and therefore a more reliable species-specific marker.     

Ultrastructural localization of the calcium-binding protein parvalbumin in neurons of the song system of the zebra finch,Poephila guttata

Summary The distribution of parvalbumin (PV) within neurons of the vocal motor nucleus hyperstriatum ventralepars caudalis (HVc) was investigated in the forebrain of adult male zebra finches by means of light and electron microscopy using the indirect immunoperoxidase technique. Parvalbumin-reaction product was located in the amorphous material of perikarya, dendrites and nuclei, and associated to microtubuli, postsynaptic densities and intracellular membranes; it was found in some axons and Gray type-2 boutons, but rarely in type-1 boutons and never in the Golgi apparatus. These observations suggest that parvalbumin may regulate calcium-dependent processes at the postsynaptic membrane and in the cytosol. Furthermore, the partial association of parvalbumin to microtubuli points to an involvement in calcium-dependent tubular functions. Calcium currents and microtubular assembly or transport may be relevant for the known functions of HVc in song learning.     

All "chick-a-dee" calls are not created equally. Part I. Open-ended categorization of chick-a-dee calls by sympatric and allopatric chickadees

Researchers trained 24 black-capped (Poecile atricapillus) and 12 mountain (P. gambeli) chickadees in an operant conditioning task to determine if they use open-ended categorization to classify "chick-a-dee" calls, and whether black-capped chickadees that had experience with mountain chick-a-dee calls (sympatric group) would perform this task differently than inexperienced black-capped chickadees (allopatric group). All experimental birds learned to discriminate between species' call categories faster than within a category (Experiment 1), and subsequently classified novel and original between-category chick-a-dee calls in Experiments 2 and 3 following a change in the category contingency. These results suggest that regardless of previous experience, black-capped and mountain chickadees classify their own and the other species' calls into two distinct, yet open-ended, species-level categories.     

10种鸣禽鸣唱复杂性与发声核团体积的聚类分析

选用捕自野外和人工繁殖的10种雄性成鸟(一年龄以上)作为实验材料。当鸟适应环境后录音,用VS-99语音工作站软件进行声谱分析。鸣唱的复杂性采用语句短语总数、短语的音节数之和、短语的音节种类数之和、每个短语中所含的平均音节数、每个短语中所含的平均音节种类数、每种鸣禽最长短语的音节数和最长短语的音节种类数7项指标表示。然后测定前脑的上纹状体腹侧尾端(HVC)、古纹状体粗核(RA)以及嗅叶的X核(Areax)3个主要鸣唱控制核团的体积。最后分别对10种鸣禽3个发声控制核团体积和鸣唱复杂性的7项指标进行聚类分析。10种鸣禽的7项指标值相差较大,即使同一科也如此。蒙古百灵的3种核团体积比值均最大,其次是金丝雀和黄喉鹉。10种鸣禽鸣唱语句复杂性的7个指标和3种核团体积聚类分析树形图显示的结果各不相同;仅RA和Areax核团体积的树形图显示蒙古百灵远离其他9种鸣禽,与现代分类学和DNA分析得到的进化树一致。     

鸣禽鸟发声行为的激素调节

讨论了性类固醇激素对鸣食发声行为及其神经回路的影响,从细胞回路水平,行为水平对性激素在幼年鸣食发声学习和成年鸣食鸣啭可塑性中的作用进行了全面论述,介绍了国内外在鸣禽发声这一研究领域的最新进展,对深入开展动物学习记忆神经机制的研究具有借鉴作用。     

Molecular clocks and evolutionary relationships: Possible distortions due to horizontal gene flow

Summary This paper discusses recent evidence suggesting that genetic information from one species occasionally transfers to another remotely related species. Besides addressing the issue of whether or not the molecular data are consistent with a wide-spread influence of horizontal gene transfer, the paper shows that horizontal gene flow would not necessarily preclude a linear molecular clock or change the rate of molecular evolution (assuming the neutral allele theory). A pervasive influence of horizontal gene transfer is more than just consistent with the data of molecular evolution, it also provides a unique explanation for a number of possibly conflicting phylogenies and contradictory clocks. This phenomenon might explain why some protein clocks are linear while the superoxide dismutase clock is not, how the molecular data on the phylogeny of apes and Australian song birds are not necessarily in conflict with those based on morphology, and, finally, why the mycoplasmas have an accelerated molecular clock.     

Patterns of phenological changes in migratory birds

The phenology of avian migration appears to be changing in response to climate change. Seemingly contradictory differences in the timing of these annual cycles have been reported in published studies. We show that differences between studies in the choice of songbird species, as well as in the measurements of migration phenology, can explain most of the reported differences. Furthermore, while earlier spring arrival is evident across these studies, trends in timing of departure show large variation between species and according to individual timing of migration (early-arriving vs. late-departing individuals). Much of the variation in departure between species could be explained by each species’ migratory status. We present a detailed analysis of migrants recorded at a Danish migration site, and reveal that although shifts in migration timing can be demonstrated for almost all species, these shifts are either most pronounced in the early arriving/late departing individuals or the changes are similar. Thus most individuals do not seem to change their breeding-area residence time (BART). As BART is likely to reflect ecologically important factors, e.g. number of clutches, we expect that only small effects have been exerted on the breeding ecology of the studied species in the time period investigated. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

新纹状体巨细胞核外侧部（LMAN）与鸣禽鸣唱学习可塑性

鸣禽鸣唱控制系统的前端脑通路（anterior forebrain pathway, AFP）在鸣唱学习中发挥着重要作用。新纹状体巨细胞核外侧部（lateral magnocellular nucleus of the anterior neostriatum, LMAN）是AFP的最后一级输出核团,AFP中的信号通过LMAN传导到弓状皮质栎核（robust nucleus of the arcopallium, RA）,与高级发声中枢（high vocal centre,HVC）共同调节RA的活动,从而影响鸣禽的发声行为。LMAN可能通过其与RA的单突触连接来影响鸣唱可塑性。文章对近年来LMAN在鸣唱学习可塑性方面的研究进行综述。     

白腰文鸟发声行为的性别差异及其机制

通过声谱分析,研究了５－１２０日龄雌、雄白腰文鸟（Lonchura striata swinhoei)的声谱变化,及该时段３个主要发声控制核团）ＨＶＣ、ＲＡ、Ａrea X)体积、睾丸（睾酮）的相应改变。结果如下：①４５日龄以前,雌雄鸟只能发出简单鸣叫（call),鸣声基本不会鸣唱。②雄性ＨＶＣ,ＲＡ,ＡreaX体积均比雌性大２－６部。３个核团的大小发育不完全一致。各核团的快速生长期与鸣唱学习的主要时段（６０－１２０日龄）不同步,说明核团的个体发育可能不完全受发声行为的影响。③睾丸的充分发育（１２０日龄后）及血液中具有较高的睾酮水平是雄鸟发出成熟鸣唱语句的重要条件。     

10种鸣禽控制鸣啭神经核团大小与鸣唱复杂性的相关性

为进一步揭示鸣禽鸣唱行为的神经生物学机制 ,本实验先对 8个科 10种鸣禽的鸣唱行为进行了观察和录音 ,并借助声谱软件分析了每种鸣禽的鸣唱复杂性。鸣唱语句复杂性的评价指标包括 :短语总数、每个短语中所含的平均音节数及音节种类数、所有短语的总音节数及音节种类数、最长短语的音节数及音节种类数。然后 ,测定了前脑三个鸣啭学习控制核团和一个与发声无关的视觉参考核团体积 ,分析了鸣唱语句复杂性和这些核团大小间的相关关系。结果表明 :1)HVC和HVC/Rt与 7种鸣唱语句复杂性指标无关 ;RA和RA/Rt与总音节种类数相关 ;AreaX与总音节数及音节种类数相关 ;2 )HVC/RA和HVC/X比值与多个鸣唱语句复杂性指标相关。结果提示 :鸣禽鸣唱复杂性不同特征可能受不同神经控制