Ecological causes and consequences of bird orientation

Summary An advanced orientation capability offers possibilities for birds to optimize movement patterns in a wide variety of ecological situations. The adaptive significance of different patterns of angular dispersion and of orientation responses to topography and sociality are elucidated. The orientation capacity is characterized by flexibility, exemplified by reorientation promoting safety and restoration of fat reserves during migration. There are also limitations to the orientation process, leading to costs of migration through mis- or disorientation, and to constraints on the evolution of routes and timing of migratory flights. Young migrants may acquire an erroneous compass sense, and misorient several thousands of kilometers off their normal course. Widespread and dense fog of long duration causes disorientation and mortality among land birds migrating over the sea. Orientational constraints in the evolution of migration routes may be most easily disclosed at high geographic and magnetic latitudes. Here the birds are faced with special difficulties in using their celestial as well as their magnetic compasses. The sun compass could be used for great circle orientation, but observed spring flight trajectories of high arctic shorebirds and geese seem to conform with rhumbline routes.     

Wind and orientation of migrating birds: A review

Summary Migratory flights are strongly affected by wind, and birds have developed many adaptations to cope with wind effects. By day, overland migrants at high altitudes may often allow crosswinds to drift their tracks laterally from the preferred heading. In contrast, many birds at low altitude adjust their headings to compensate for drift, and may overcompensate to allow for previous drift. The relative motion of landscape features is probably used to sense drift, at least by day. By night, some overland migrants compensate fully for drift but others do not; no pattern is obvious. Over the sea, compensation is rarely if ever total; wave patterns may allow partial compensation. Other adaptations can include reduction of drift by flying at times and/or altitudes without strong crosswinds. Some birds recognize the need to change course to allow for previous wind displacement, and reorient at least roughly toward the original route or destination. Some juveniles en route to previously-unvisited wintering grounds seem to have this ability, but corroboration is needed. Such reorientation may not require a true navigation ability. However, some birds have unexplained abilities to sense the wind while aloft.     

Olfactory navigation in birds

Summary Many bird species rely on an osmotactic mechanism to find food sources even at a considerable distance. Pigeons also rely on local odours for homeward orientation, and they integrate those perceived during passive transportation with those at the release site. It is possible to design experiments in which birds are given false olfactory information, and predictions about the effects of this can be made and tested. Pigeons build up their olfactory map by associating wind-borne odours with the directions from which they come; this was shown by experiments which aimed at preventing, limiting or altering this association. Some objections have been made to this conclusion; namely that even anosmic pigeons are sometimes homeward oriented, that they may be demotivated in flying or disturbed in their general behaviour, and that olfactory cues may be only one component of pigeo's navigational repertoire. The most recent experiments, however, confirm that pigeons derive directional information from atmospheric odouts. The lack of any knowledge about the chemical nature and distribution of the odorants which allow pigeons to navigate hinders progress in this area of research.     

Evolutionary aspects of orientation and migration in birds

Summary Evolutionary aspects of avian migratory orientation and navigation are reviewed. A theoretical approach to the evolution of complex (endogenously programmed) migratory behavior is presented using the comparative method of ordering a progression in existing behavioral characteristics from dispersal, to facultative migration, to obligate migration.     

Genetic transmission of migratory behavior into a nonmigratory bird population

Summary Crossbreeding experiments with blackcaps from a nonmigratory population (of the Cape Verde Islands) and a migratory population (from southern Germany) demonstrated that the urge to migrate as well as orientation behavior can be transmitted rapidly into a nonmigratory bird population and thus have a substantial genetic basis.     

A magnetic pulse leads to a temporary deflection in the orientation of migratory birds

Migratory Australian Silvereyes were treated with a strong magnetic pulse designed to alter the magnetization of the small magnetite particles that are found in birds' heads. Prior to the treatment, the birds preferred the northeasterly migratory direction. The pulse initially resulted in a 90° clockwise shift of orientation; however, within about a week, the birds seemed to return to their original headings. These findings, which seem to suggest an involvement of magnetite in migratory orientation, are in contrast with previous findings which indicated that it is a light-dependent process. They are discussed in view of the current concepts on magnetoreception and on the role of magnetic information in avian orientation.     

Magnetic inclination compass: A basis for the migratory orientation of birds in the Northern and Southern Hemisphere

We conducted orientation experiments with Silvereyes,Zosterops lateralis, Australian passerine migrants, to see whether birds living in the Southern Hemisphere in a magnetic field with an upward inclination orient in the same way as birds in the Northern Hemisphere that experience a downward inclination of the magnetic field. Tested indoors in the local geomagnetic field, the birds preferred southerly directions corresponding to their migratory direction in spring. In a magnetic field with a reversed vertical component, they reversed their directional tendencies. This shows that the magnetic compass of Silvereyes also functions as an inclination compass based on the inclination of the field lines instead of the polarity.     

Magnetic orientation and celestial cues in migratory orientation

Summary Young birds on their first migration possess innate information on the direction of their migration route. It is present in two forms, using celestial rotation and the geomagnetic field as references. These two systems, together with information provided by factors associated with sunset, interact in a complex way to establish the migratory direction. During ontogeny, celestial rotation appears to be dominant; during migration, however, celestial cues appear to be controlled by the magnetic field. The factors associated with sunset — the view of the setting sun, the characteristic pattern of polarized light — are important secondary cues which seem to derive their directional significance from the magnetic field. Their role appears to be more variable, with possible species-specific differences. During spring migration and later autumn migrations, flying in the migratory direction is complemented by navigational processes which enable the birds to return to a specific home site known from previous stays.     

Experimental studies of the development of migratory orientation mechanisms

Summary Recent experimental studies (since ca 1985) on the ontogeny of orientation mechanisms in migratory birds are reviewed. The processes and interactions are synthesized into a framework that may help identify critical research questions. Birds that grow up in the earth's magnetic field develop the ability to perform appropriate migratory orientation even in the absence of any experience with relevant visual cues. In two species, large changes in direction during the course of migration seem to be controlled by an endogenous time program. In one of these, the pied flycatcher (Ficedula hypoleuca), the correct magnetic orientation seems to occur only when the magnetic fields appropriate to the latitudes encountered en route were experienced at the proper seasonal time. The magnetic compass may be modified by visual experience with either the daytime or night sky. Celestial rotation may be the calibrating reference in this case, as it is in the development of the star compass. Young Savannah sparrows (Passerculus sandwichensis) learn to perform compass orientation at sunset based on polarized skylight. This compass capability seems to be calibrated by magnetic directions. Some problems of experimental design and the interpretation of results from experiments on development are discussed.     

Initial orientation of homing pigeons: different sensitivity to altered magnetic fields in birds of different countries

Summary In experiments performed in Italy, altered magnetic fields were effective in biasing the initial orientation of Italian pigeons but not that of German pigeons raised in Italy, suggesting a genetic difference between the two bird stocks.We are grateful to Dr H. G. Wallraff who kindly supplied the German pigeons used in our experiments and gave useful suggestions.     

高纯铝再结晶晶界面的择尤取向

相比于传统的晶体择尤取向（晶体织构,简称织构）,晶界面择尤取向是一个新的科学问题.系统地研究晶界面择尤取向的形成规律和演化机制对合理调控显微组织结构以显著改善材料的各种使用性能具有非常重要的科学意义和应用价值.本文利用基于体视学原理和电子背散射衍射技术的晶界特征分布五参数表征分析方法,研究了冷轧变形高纯铝（99.99%）再结晶晶界面的择尤取向问题.结果表明,在再结晶及晶粒长大过程中,晶界面择尤取向由最初的{2 2 3}晶面转变为{1 1 1}晶面,最后取向在{1 0 0}晶面上.分析指出,冷轧变形高纯铝再结晶组织中,小角度晶界（取向差介于2°~15°）是其晶界构成的主体部分;在晶粒长大过程中,晶体织构由{1 1 0}〈1 1 2〉黄铜织构为主转变为以{0 1 1}〈1 0 0〉高斯织构和{0 2 3}〈1 0 0〉织构共存为主,受晶面能和晶体织构的影响,小角度晶界一般择尤取向于可形成能量较低的倾侧型小角度晶界所对应的晶面上.这是导致高纯铝再结晶晶界面择尤取向随晶粒长大而发生上述规律性变化的主要原因.     

More on the need for circadian,circaseptan and circannual optimization of cyclosporine therapy

Summary Cyclosporine chronotherapy of pancreas-allotransplanted rats revealed, beyond a circadian stage-dependence of equal daily doses, further gain in graft function from doses varying from day to day with an about 7-day periodicity, the first highest dose being given on the 3rd or 5th day after surgery.     

Conceptual approaches to avian navigation systems

Summary The general basis of migratory orientation in birds is most probably an endogenous time-and-direction program. Directions are selected with respect to celestial and geomagnetic clues. Using these clues, a bird may reach a large population-specific area; however, it will hardly be able to find a particular location, for instance its previous breeding site. Homing to a familiar site over several hundred kilometres of unfamiliar terrain appears to be based on the smelling of atmospheric trace compounds. Conceptual approaches to the mechanism of olfactory navigation have as yet only reached an early state of speculation.     

Depolarization of natural skylight disrupts orientation of an avian nocturnal migrant

Summary Given a view of clear evening skies, migratory blackcaps (Aves:Sylvia atricapilla) orient appropriately in the absence of meaningful information from the geomagnetic field. When the intensity of natural skylight polarization patterns was reduced with pseudodepolarizers by over 90%, test birds were disoriented, and their migratory restlessness in autumn was drastically reduced.     

Strain differences in the pattern and intensity of wheel running activity in laboratory rats

Summary Wheel running activity rhythms of three inbred rat strains, ACI/Ztm, BH/Ztm, and LEW/Ztm, were compared in order to evaluate the effect of genetic differences on circadian rhythm parameters. Significant strain differences were found in the general pattern of the activity rhythms and their characteristic periodicities as well as in the amount and duration of wheel running activity and the timing of activity onsets and offsets. The results suggest that genetic differences exist in the coupling of the multiple circadian oscillators that generate the overall pattern of wheel running activity.     

Population genetics of a colonizing lizard: Loss of variability in introduced populations ofPodarcis sicula

Allozyme electrophoresis was used to study the genetic variability (proportion of polymorphic loci and heterozygosity) in insular populations (Corsica, Elba, Montecristo, Marettimo, Pantelleria) of the lacertid lizardPodarcis sicula. These populations were presumed to have originated from episodes of accidental anthropogenic introduction. In order to test the hypothesis of a man-aided colonization and to provide comparative data, heterozygosity and polymorphism were also estimated in autochthonous populations ofP. sicula from the Italian peninsula and Sicily. In each case, the presumed introduced population showed levels of genetic variability significantly lower than those detected in the autochthonous ones. Very little genetic differentiation was found among native and presumed colonist populations, Nei's standard genetic distances ranging from 0.001 to 0.009. These results strongly support the hypothesis thatP. sicula was only recently introduced to the studied islands, and provide additional evidence of reduced genetic variability due to founder effect in insular populations originating from episodes of human transportation.     

Common antigenic properties of a g-type (goose) and a c-type (duck) egg white lysozyme: Antibody responses in rabbits and mice

Embden goose (GEWL) and Barbary duck (DEWL) egg white lysozymes possess different amino acid sequences corresponding to the g-type and c-type, respectively. GEWL was shown to be a better immunogen than DEWL in both rabbits and mice. The antigenicity of the two lysozymes was tested using different technique (i.e. indirect ELISA, inhibition tests and immunoabsorption experiments). Injection of either GEWL or DEWL into rabbits and mice induced both specific antibodies and cross-reacting antibodies. Moreover, anti-GEWL antibodies, in contrast to anti-DEWL antibodies, did not cross-react with hen egg white lysozyme (HEWL), a c-type lysozyme. While the structure of GEWL was not modified after binding to plastic, DEWL was denaturated, but it did keep some native epitopes. It was concluded that g-type and c-type lysozymes, which have different amino acid sequences, exhibit strong common antigenic properties.     

Genetic and photoperiodic control of an avian reproductive cycle

European blackcaps,Sylvia atricapilla, with one breeding season per year, have a single-peaked annual testes cycle. However, African conspecifics from the Cape Verde Islands with two breeding seasons per annum demonstrate a two-peaked cycle. Both population-specific cycles reflect differences in the respective endogenous circannual rhythms. Experimental hybridization of birds of the two populations resulted in an intermediate pattern of testes cycle, thus demonstrating that there are genetic components for some temporal aspects in an avian reproductive cycle. Another characteristic of the African birds, their extremely rapid juvenile development and early sexual maturity (at an age of 5–6 months) proved largely to be a photoperiodic (short-day) effect in birds hatched in autumn. The same effect could also be induced in European conspecifics exposed to correspondingly short day-lengths.     

Pharmacogenetics and disease genetics of complex diseases

Advances in technologies and the availability of a single nucleotide polymorphism (SNP) map are beginning to show the true potential for the human genome project to affect patient healthcare. A whole genome scan, the use of 100,000–300,000 SNPs across the genome, is now possible. Use of traditional approaches and the whole genome scan will result in identification of disease susceptibility genes and development of many new treatments in the longer term. In the shorter term, the goal will be to predict those patients at risk to experience an adverse reaction or those with a high probability for improved efficacy (i.e. pharmacogenetics). As progress is made in the area of disease genetics and pharmacogenetics, our understanding of disease susceptibility and its interrelationship with drug response will improve, making targeted therapy (i.e. the right drug to the right patient) a reality.Received 19 December 2002; received after revision 14 February 2003; accepted 20 February 2003