Sensory basis of bird orientation

Summary Sensory information which may be essential for the complex process of orientation of birds is described in this article. The use of vibrational, visual, chemical, olfactory, magnetic cues and their receptive mechanisms, as far as they are known, are explained. Special reference is given to the behavioral and physiological aspects of magnetic sensitivity.     

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.     

Endogenous control as a possible basis for varying migratory habits in different bird populations

Summary In handraised experimental groups of 4 populations ofSylvia atricapilla, it was found that the development of migratory restlessness under constant conditions was a fairly good reflection of the different (typical, partial, and non-) migratory habits of the populations. Thus, the different migratory habits seem to be endogenously preprogrammed and genetic in origin. The results of a preliminary cross-breeding experiment are at least compatible with the assumption that partial migratory habit in the blackcap is due to polymorphism.Supported by the Deutsche Forschungsgemeinschaft; 25th paper of the warbler program of the institute.     

Genetic basis of moult,wing length,and body weight in a migratory bird species,Sylvia atricapilla

Summary In hand-raised groups of 4 populations of Blackcaps, different patterns of juvenile moult as well as differences in wing length and body weight, adaptive to the various degrees of migratory performance, could be demonstrated. 33 F₁-hybrids which were produced experimentally with 2 of these groups (1 African×1 European) showed an intermediate expression of these adaptations relevant to migration, indicating that these physiological and morphological features are under strong direct genetic control.     

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.     

Non-visual orientation inTalitrus saltator

Zusammenfassung Die Versuche vonPapi undPardi ^1–6 wurden mitTalitrus saltator wiederholt. Auch unter völligem Lichtabschluss zeigten die Tiere ein noch ähnlich orientiertes Verhalten. Ausschaltung des erdmagnetischen Feldes bis auf 50 konnte die Orientierung im Dunkeln nicht aufheben.     

Spatiotemporal programs and genetics of orientation

Summary A number of migratory bird species have endogenous annual rhythms that regulate the entire annual cycle including the migratory portion. Moreover, captive migrants display inherited migratory activity; this could theoretically also be used by free-living migrants as a time-program for migration. Finally, this heritable migratory activity is oriented in a seasonally appropriate direction even in naive birds. These, characteristics should enable inexperienced migrants isolated from contact with experienced conspecifics to utilize a heritable vector-navigation program to migrate from the breeding grounds to the winter quarters. That is, migrants should reach goal areas they have never experienced by migrating in programmed directions, for as long a period as the genetically fixed time-program for migratory activity induces them to do so. The time-course of migration as established by trapping stations, theoretical influences of environmental variables on migratory programs, and also compensatory behavior and migratory backup measures, are discussed. The present evidence supports the view that a large number of migrants are essentially brought to their wintering areas by vector-navigation systems.     

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.     

Molecular basis of Alzheimer's disease

Despite an exponential production of data, Alzheimer's disease (AD) remains an enigma. Unresolved questions persist in the face of the heterogeneity of this neuropathology. Recent progress in understanding mechanisms for AD results from the study of amyloid precursor protein (APP) metabolism and the involvement of senile plaque-associated proteins. In addition to the amyloid cascade hypothesis, alternative schemes emerge, in which the amyloid peptide is not the primary effector of the disease. Perturbations of vesicular trafficking, the cytoskeletal network, and membrane cholesterol distribution could be central events. Furthermore, since the physiological role of APP, presenilins, and apolipoprotein E in the central nervous system are not completely understood, their involvement in AD etiology remains speculative. New actors have to be found to try to explain sporadic cases and non-elucidated familial cases.     

Structural basis of nucleolar function

Zusammenfassung Es scheint ein fundamentaler Zusammenhang zwischen Struktur und Funktion des Nukleolus vorhanden zu sein. Die Spätphase des Hauptnukleolus hat eine Doppelstruktur. Die beobachtete Nukleolusvermehrung zeigt, dass der Nukleolus ein aktives Gebiet für RNS und Proteinsynthese ist. Die Übertragung der Nukleolusstoffe vom Kern ins Cytoplasma wird diskutiert.     

Risk-sensitive foraging by a migratory bird (Dendroica coronata)

Cellular and Molecular Life Sciences - Because migration is a period of exceptional energy demand, individuals in migratory disposition should be particularly sensitive to variability in food...