Polarized light cues underlie compass calibration in migratory songbirds

Migratory songbirds use the geomagnetic field, stars, the Sun, and polarized light patterns to determine their migratory direction. To prevent navigational errors, it is necessary to calibrate all of these compass systems to a common reference. We show that migratory Savannah sparrows use polarized light cues from the region of sky near the horizon to recalibrate the magnetic compass at both sunrise and sunset. We suggest that skylight polarization patterns are used to derive an absolute (i.e., geographic) directional system that provides the primary calibration reference for all of the compasses of migratory songbirds.     

Magnetic direction finding: evidence for its use in migratory indigo buntings

The orientational capabilities of caged migratory indigo buntings were studied under differing magnetic field conditions. When tested in a situation allowing minimal exposure to visual cues but in the presence of the normal geomagnetic field, the birds demonstrated a significant orientation in the appropriate migratory direction (to the north). When the horizontal component of the magnetic field was deflected clockwise 120 degrees by activation of Helmholtz coils surrounding the cage, the orientation of the buntings shifted accordingly (clockwise to geographic east-southeast). These results suggest that indigo buntings are not only able to detect the geomagnetic field, but also can use this information in the finalization of their migratory direction.     

The movement of aquatic mercury through terrestrial food webs

Mercury has contaminated rivers worldwide, with health consequences for aquatic organisms and humans who consume them. Researchers have focused on aquatic birds as sentinels for mercury. However, trophic transfer between adjacent ecosystems could lead to the export of aquatic mercury to terrestrial habitats. Along a mercury-contaminated river in Virginia, United States, terrestrial birds had significantly elevated levels of mercury in their blood, similar to their aquatic-feeding counterparts. Diet analysis revealed that spiders delivered much of the dietary mercury. We conclude that aquatic mercury pollution can move into terrestrial habitats, where it biomagnifies to levels in songbirds that may cause adverse effects. Rivers contaminated with mercury may pose a threat to the many bird species that feed on predatory invertebrates in adjacent riparian habitats.     

Two magnetoreception pathways in a migratory salamander

Male eastern red-spotted newts (Notophthalmus viridescens) under controlled laboratory conditions exhibit unimodal magnetic compass orientation either in a trained compass direction or in the direction of their home pond. If the vertical component of the magnetic field is inverted, newts exhibiting the simple-compass response undergo a 180 degree reversal in orientation, whereas newts orienting in the home direction are unaffected by this treatment. These results indicate that newts use an axial compass mechanism for simple-compass orientation similar to that found in migrating birds. However, a distinct magnetoreception pathway with polar response properties is involved in homing and is possibly linked in some way to the navigational map.     

Decline of DDT residues in migratory songbirds

Analyses of ten species of migratory songbirds killed when the birds flew into television towers in Florida showed a progressive decline in the concentration of DDT and its metabolites (DDD and DDE) in their fat depots for the period 1964 to 1973. This decline is apparently correlated with the decreased usage of DDT in the United States during the same time.     

Migration along orthodromic sun compass routes by arctic birds

Flight directions of birds migrating at high geographic and magnetic latitudes can be used to test bird orientation by celestial or geomagnetic compass systems under polar conditions. Migration patterns of arctic shorebirds, revealed by tracking radar studies during an icebreaker expedition along the Northwest Passage in 1999, support predicted sun compass trajectories but cannot be reconciled with orientation along either geographic or magnetic loxodromes (rhumb lines). Sun compass routes are similar to orthodromes (great circle routes) at high latitudes, showing changing geographic courses as the birds traverse longitudes and their internal clock gets out of phase with local time. These routes bring the shorebirds from high arctic Canada to the east coast of North America, from which they make transoceanic flights to South America. The observations are also consistent with a migration link between Siberia and the Beaufort Sea region by way of sun compass routes across the Arctic Ocean.     

Vocalization evoked from the optic lobe of a songbird

Vocalizations from songbirds have been evoked by electrical stimulation of the torus. These vocalizations resemble the normal alarm and scolding calls of the species. The torus of the birds appears to correspond functionally and anatomically to the mammalian central gray matter.     

惠州鸟类资源调查

2005年3月～2012年12月,惠州记录到鸟类18目、58科、299种。其中,雀形目鸟类27科、151种,占总数的50.50%;非雀行目鸟类31科、148种,占总数的49.50%。国家重点保护鸟类Ⅰ级2种,Ⅱ级37种。我国特有种2种。CITES记录的鸟类11种,《中国濒危物种红皮书》中的鸟类23种。留鸟157种,占总数的52.51%;冬候鸟90种,占总数的30.10%;夏候鸟37种,占总数的12.37%;旅鸟或迷鸟15种,占总数的5.02%。东洋界种155种,占总数的51.84%;古北界种107种,占总数的35.79%;广布种37种,占总数的12.37%。鸣禽151种,占总数的50.50%;湿地水鸟73种,占总数的24.7%。麻雀、白喉红臀鹎等15种鸟类是惠州的优势种,占总数的5.01%。     

A specialized forebrain circuit for vocal babbling in the juvenile songbird

Young animals engage in variable exploratory behaviors essential for the development of neural circuitry and adult motor control, yet the neural basis of these behaviors is largely unknown. Juvenile songbirds produce subsong-a succession of primitive vocalizations akin to human babbling. We found that subsong production in zebra finches does not require HVC (high vocal center), a key premotor area for singing in adult birds, but does require LMAN (lateral magnocellular nucleus of the nidopallium), a forebrain nucleus involved in learning but not in adult singing. During babbling, neurons in LMAN exhibited premotor correlations to vocal output on a fast time scale. Thus, juvenile singing is driven by a circuit distinct from that which produces the adult behavior-a separation possibly general to other developing motor systems.     

Orientation by pigeons: is the sun necessary?

Although most recent hypotheses of pigeon homing have assigned an essential role to the sun, there has been some evidence suggesting that the sun is not essential. Two series of releases were designed to examine the question more carefully. Birds whose internal clocks had been shifted 6 hours were used in the critical tests. Under sun, the vanishing bearings of the clock-shifted birds were deflected in the direction predicted by a hypothesis of use of the sun as a simple compass. By contrast, under total overcast the bearings of both the clock-shifted and the control birds were homeward oriented and there was no difference between them, even at a release site the birds could never have seen previously. Therefore it is concluded that the sun is used as a compass when it is available, but that the pigeon navigation system contains sufficient redundancy to make accurate orientation possible in the absence of both the sun and familiar landmarks; the orientational cues used under such conditions do not require time compensation. This conclusion is in complete disagreement with the Matthews sun-arc hypothesis of pigeon navigation, and it makes necessary a major reformulation (at the very least) of the other principal hypothesis, that of Kramer.     

Partner-specific odor recognition in an Antarctic seabird

Among birds, the Procellariiform seabirds (petrels, albatrosses, and shearwaters) are prime candidates for using chemical cues for individual recognition. These birds have an excellent olfactory sense, and a variety of species nest in burrows that they can recognize by smell. However, the nature of the olfactory signature--the scent that makes one burrow smell more like home than another--has not been established for any species. Here, we explore the use of intraspecific chemical cues in burrow recognition and present evidence for partner-specific odor recognition in a bird.     

海南岛湿地鸟类的资源调查及多样性研究

为了掌握海南岛湿地珍稀濒危鸟种和常见鸟类的基础信息，于 2020年12月和2021年5月在岛内32处湿地开展了鸟类调查，共行走样线215条，完成调查样点157个，记录鸟类206种34 673只，隶属17目61科，其中国家1级保护鸟类4种，国家2级保护鸟类34种。涉禽和鸣禽的数量占多数，分别占59.9%、32.2％。优势和常见鸟类共28种，如白鹭Egretta garzetta、丝光椋鸟Spodiopsar sericeus、蒙古沙鸻Charadrius mongolus、牛背鹭Bubulcus coromandus等，这28种鸟类记录占海南岛湿地整个鸟类记录总数的78%。Shannon-Wiener指数以河流湿地最高（5.225），湖泊湿地最低（2.843）；Pielo指数以沼泽湿地最高（0.776），人工湿地最低（0.618）；鸟类相似度以河流湿地和人工湿地最高（0.67），近海与海岸湿地和湖泊湿地最低（0.22）。     

Orientation of Migratory Restlessness in the White-Crowned Sparrow

Individuals of two migratory races of white-crowned sparrows (Zonotrichia leucophrys) caged under an open sky showed a pronounced orientation in their night restlessness during normal periods of migration for the species. In August and September 1958 most birds showed a southerly orientation at night; daytime activity was random to somewhat northerly. In April and May 1959 most birds showed a strong northerly orientation at night; daytime activity was random to somewhat southerly (1).     

Conflicting evidence about long-distance animal navigation

Because of conflicting evidence about several fundamental issues, long-distance animal navigation has yet to be satisfactorily explained. Among the unsolved problems are the nature of genetic spatial control of migration and the relationships between celestial and magnetic compass mechanisms and between different map-related cues in orientation and homing, respectively. In addition, navigation is expected to differ between animal groups depending on sensory capabilities and ecological conditions. Evaluations based on modern long-term tracking techniques of the geometry of migration routes and individual migration history, combined with behavioral experiments and exploration of the sensory and genetic mechanisms, will be crucial for understanding the spatial principles that guide animals on their global journeys.     

Celestial rotation: its importance in the development of migratory orientation

Three groups of indigo buntings were hand-raised in various conditions of visual isolation from celestial cues. When they had been prevented from viewing the night sky prior to the autumn migration season, birds tested under planetarium skies were unable to select the normal migration direction. By contrast, when they had been exposed as juveniles to a normal, rotating, planetarium sky, individuals displayed typical southerly directional preferences. The third group was exposed to an incorrect planetarium sky in which the stars rotated about a fictitious axis. When tested during the autumn, these birds took up the "correct" migration direction relative to the new axis of rotation. These results fail to support the hypothesis of a "genetic star map." They suggest, instead, a maturation process in which stellar cues come to be associated with a directional reference system provided by the axis of celestial rotation.     

广东翁源青云山省级自然保护区的鸟类多样性及群落特征分析

【目的】了解广东翁源青云山省级自然保护区鸟类的群落组成与多样性。【方法】于2021年,采用样线法对青云山保护区中林区、公路、村庄和水库4种生境的鸟类群落进行实地调查,同时访问调查本地居民和保护区工作人员、查阅保护区本底资料和科考报告,查找中国知网、中国观鸟记录中心等有关记录。【结果】本研究共统计到鸟类17目51科168种。区系组成：东洋界103种,广布种40种,古北界25种。居留型组成：留鸟119种,候鸟43种(冬候鸟27种、夏候鸟16种),旅鸟6种。生态类型以鸣禽为主,食性组成以杂食性和食虫为主。鸟类优势种包括淡眉雀鹛Alcippe hueti、栗背短脚鹎Hemixos castanonotus、赤红山椒鸟Pericrocotus speciosus。国家一级重点保护鸟类2种,国家二级重点保护鸟类30种。不同生境鸟类的平均生物量从高到低依次为：林区、村庄、水库、公路。多样性指数分析表明,村庄生境的Shannon-Wiener多样性指数(3.24)、Pielou均匀度指数(0.61)最高;公路生境的Margalef丰富度指数(7.34)最高;村庄和公路生境的Simpson优势度指数(0...     

Aversive learning enhances perceptual and cortical discrimination of indiscriminable odor cues

Learning to associate sensory cues with threats is critical for minimizing aversive experience. The ecological benefit of associative learning relies on accurate perception of predictive cues, but how aversive learning enhances perceptual acuity of sensory signals, particularly in humans, is unclear. We combined multivariate functional magnetic resonance imaging with olfactory psychophysics to show that initially indistinguishable odor enantiomers (mirror-image molecules) become discriminable after aversive conditioning, paralleling the spatial divergence of ensemble activity patterns in primary olfactory (piriform) cortex. Our findings indicate that aversive learning induces piriform plasticity with corresponding gains in odor enantiomer discrimination, underscoring the capacity of fear conditioning to update perceptual representation of predictive cues, over and above its well-recognized role in the acquisition of conditioned responses. That completely indiscriminable sensations can be transformed into discriminable percepts further accentuates the potency of associative learning to enhance sensory cue perception and support adaptive behavior.     

北京温榆河生态廊道春季鸟类物种构成与多尺度环境因子的关系

  目的  城市化进程加剧了城市绿地的破碎化,严重威胁了城市鸟类多样性,河流生态廊道在鸟类栖息地保护方面起到重要作用。然而,各类群鸟类多样性受多尺度环境因子的共同影响,针对不同类群的城市生态廊道鸟类栖息地格局优化与栖息地营造亟待理论研究的支撑。本文在分析北京温榆河生态廊道春季鸟类物种构成特征的基础上,对景观格局、栖息地斑块和微栖息地3个尺度下的环境因子对各类群鸟类物种构成的影响进行综合分析,以期深入了解影响鸟类栖息地选择的环境因素,为城市鸟类多样性保护和城市河流生态廊道栖息地建设提供参考。  方法  于2019年春季对温榆河生态廊道内部鸟类物种构成和植物群落结构特征进行实地调研,并对流域栖息地类型进行目视解译和格局分析,通过冗余分析法（RDA）对鸟类物种构成特征与多尺度环境因子的相关性进行分析。  结果  50 ~ 200 m内的景观格局环境因子对廊道内鸟类总体物种构成解释度最高。鸣禽类群物种构成与微栖息地内的乔木均匀度、小范围内的水体、湿地面积以及较大范围内的草地、落叶林地相关指数相关;陆禽类群物种构成与耕地和灌丛相关;游禽和涉禽类群物种构成与较小范围内的水体面积、湿地面积相关;猛禽与湿地水体相关性强。相同生态类群下不同居留型鸟类与环境因子之间的相关关系存在差异。多数鸟类的多度与100 m范围内湿地面积、湿地最大斑块占比和湿地结合度以及2 000 m范围内水体分离度等指数正相关。  结论  不同类群鸟类与各环境因子的关系存在差异,但水体和湿地相关指数对河流生态廊道内各生态类群鸟类均有影响。在未来的城市生态廊道建设中,建议考虑不同类群鸟类的栖息地偏好,注重廊道内部湿地水体格局的优化,针对目标物种开展鸟类栖息地营造与保护工作。      

Encoding predictive reward value in human amygdala and orbitofrontal cortex

Adaptive behavior is optimized in organisms that maintain flexible representations of the value of sensory-predictive cues. To identify central representations of predictive reward value in humans, we used reinforcer devaluation while measuring neural activity with functional magnetic resonance imaging. We presented two arbitrary visual stimuli, both before and after olfactory devaluation, in a paradigm of appetitive conditioning. In amygdala and orbitofrontal cortex, responses evoked by a predictive target stimulus were decreased after devaluation, whereas responses to the nondevalued stimulus were maintained. Thus, differential activity in amygdala and orbitofrontal cortex encodes the current value of reward representations accessible to predictive cues.