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  • 1
    Electronic Resource
    Electronic Resource
    Observations on Barnacle Goose Breeding,Branta leucopsis, in Spitsbergen 1975 (1979)
    Springer
    Journal of ornithology 120 (1979), S. 188-195 
    Details
    ISSN: 1439-0361
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung Unsere Beobachtungen an Nonnengänsen in Spitzbergen nach der Brutzeit brachten folgende Ergebnisse: Die Mauser setzte bei den nichtbrütenden Gänsen etwa 16 Tage früher ein als bei den brütenden und fiel zeitlich ungefähr mit dem Schlüpftermin der Gössel zusammen. Die Nichtbrüter bildeten große Mauserverbände in Küstennähe und unterließen fast völlig Verhaltensweisen, die dem Paarzusammenhalt dienen (Schnattern und Triumphgeschrei). Die Brüter wanderten nach dem Schlüpfen der Jungen von den Brutplätzen zu ihren Aufzuchtgebieten, wo sie sich zu kleineren Familienscharen zusammenschlossen. Diese Familienscharen nahmen im Lauf des Sommers und mit dem Einsetzen der elterlichen Mauser zahlenmäßig zu. Sowohl in den Mauser- als auch in den Familienscharen zeigten die Individuen einen starken Zusammenhalt auf engem Raum und synchrone Aktivitäten. Eine Dreifamilienschar wurde im Detail untersucht. Ein Tagesrhythmus in der zeitlichen Verteilung von Weiden, Ruhen und Ortswechsel trat nicht auf. Einem Ganter gelang es häufiger als den beiden anderen, bei Ortsveränderungen eine führende Rolle in der Schar einzunehmen. Die Ganter richteten ihre Angriffe bevorzugt auf andere Ganter und fremde Gössel, die Weibchen auf andere Weibchen. Wir konnten nicht beobachten, daß Gänse oder Gössel von Raubtieren erbeutet wurden. Adulte Gänse griffen Möwen und Raubmöwen an. Vor einem Eisfuchs begaben sich flugunfähige Gänse ins Wasser, während flugfähige Gänse ihn anhaßten.
    Notes: Summary Our observations on Barnacle geese in Spitsbergen permit the following conclusions: The non-breeding geese molted at about the same time as hatching occurred in the nesting colonies, about 16 days before the breeders' molt began. The non-breeders came together into large groups along the coast. Pair bond displays (cackling and triumph ceremonies) were infrequent in non-breeder molting flocks. Families formed small flocks after hatching and migrating to the breeding areas. The flocks grew in number as the summer progressed and the parental molt occurred. The non-breeder flocks and the family flocks were both extremely cohesive. The families in a particular flock were normally synchronized in their activities. A flock of three families was studied in detail. An analysis of activity patterns showed that no diurnal fluctuations in resting, grazing and travelling were present. One gander initiated place changes more successfully than the other two. No geese or goslings were preyed upon during our observations. Gulls and skuas were threatened by individual geese. Arctic foxes caused flightless geese to take refuge in water. Full-winged adults mobbed the foxes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01642997
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  • 2
    Electronic Resource
    Electronic Resource
    Seasonal organization of breeding and molting in the Fiscal Shrike (Lanius collaris) (1986)
    Springer
    Journal of ornithology 127 (1986), S. 79-84 
    Details
    ISSN: 1439-0361
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung Der Fiskalwürger ist die häufigste afrikanische Würgerart. Er ernährt sich von Insekten, Reptilien, kleinen Säugetieren und Vögeln. VonBrown &Britton (1980) undMacDonald (1980) wurde wegen dieser Beutevielfalt vermutet, daß er auch unter ungünstigen Umweltbedingungen (Trockenheit) brüten kann. In Nakuru, Kenya, wurde untersucht, ob jahreszeitlich bedingte Unterschiede in Brutaktivität, Gonadengröße, Mauser und in Plasmatitern von LH, T und E 2 vorhanden waren. Brutaktivität und Mauser waren mit der Hauptregenzeit korreliert. Die Brutzeit endete mit Beginn der Mauser, die von August bis Dezember dauerte. Obwohl die Gonaden bei einigen Vögeln schon während der Trockenzeit (Januar bis März) gut entwickelt waren, gab es bis zur Regenzeit keinen Hinweis auf Fortpflanzungsaktivität. Es wird angenommen, daß eine strenge Trockenzeit die Ausschüttung von Testosteron (♂) und Estradiol (♀) verhindert, ohne die Gonadengröße zu beeinflussen. In Gegensatz zu den vorher genannten Autoren wurde keine Fortpflanzungsaktivität in Trockenzeiten festgestellt. Das beruht vielleicht auf dem in einzelnen Jahren unterschiedlichen Ausmaß der Trockenzeit.
    Notes: Summary Free-living Fiscal Shrikes were investigated in Nakuru Kenya for seasonal patterns in breeding, gonadal size, molt and the plasma titers of LH, T in males and E 2 in females. Both breeding and molt were found to be seasonally restricted activities. A complete molt occurred from August to December after breeding had ceased. Although the gonads in some birds were well developed during the dry season, at the beginning of the year, no breeding was found until the onset of the heavy rains. It is proposed that severe drought inhibits reproductive activity and correspondingly the secretion of gonadal steroids (T and E 2) in Fiscal Shrikes without affecting increases in gonadal size.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01641445
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  • 3
    Electronic Resource
    Electronic Resource
    Symposium: Ornithology in Austria (1994)
    Springer
    Journal of ornithology 135 (1994), S. 269-275 
    Details
    ISSN: 1439-0361
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01639958
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  • 4
    Electronic Resource
    Electronic Resource
    Reproductive effort and costs of reproduction in female European ground squirrels (1999)
    Springer
    Oecologia 121 (1999), S. 19-24 
    Details
    ISSN: 1432-1939
    Keywords: Key words Ground squirrel ; Female ; Reproduction ; Lactation ; Gonad development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Reproductive effort, factors affecting reproductive output and costs of reproduction were studied in primiparous yearling compared to multiparous older female European ground squirrels (Spermophilus citellus). Yearling females weaned smaller litters than older ones. Litter size increased with posthibernation body mass at the expense of slightly lighter young for yearling but not for older mothers. In older females, on the other hand, emergence body mass influenced offspring mass, whereas litter size was affected by oestrus date. High reproductive effort entailed reproductive costs in terms of reduced subsequent fecundity but not subsequent survival for both yearling and older females. The production of large litters and long duration of lactation delayed subsequent oestrus, which, in turn, correlated negatively with litter size. During the second half of lactation, oestradiol levels were significantly elevated, indicating the initiation of follicular maturation processes. Oestradiol levels during that time correlated negatively with current, but positively with subsequent litter size. We therefore assume that inhibitory effects of lactation on gonadal development may mediate the negative relationship between reproductive effort and subsequent reproductive timing in adults. This effect is absent in yearlings because they are reproducing for the first time. Reproductive output in yearlings was influenced by interactions between structural growth and puberty.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050902
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  • 5
    Electronic Resource
    Electronic Resource
    Territorial spacing and interspecific competition in three species of reed warblers (1991)
    Springer
    Oecologia 87 (1991), S. 443-448 
    Details
    ISSN: 1432-1939
    Keywords: Reed warblers ; Interspecific spacing ; Territoriality ; Ecological separation ; Dominance behavior
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Ecological and temporal aspects of the occurrence and dispersion patterns in three reed warbler species were examined. This provided insight into their intra-and interspecific territoriality. Seasonal changes in the occurrence of territorial males in a reed bed along a gradient from the shore landward were studied. The results demonstrate that intra- and interspecific spacing depends on interspecific dominance and/or ecological constraints. In this case it was shown that there is competition for common habitats between reed warblers and great reed warblers, whereas the moustached warbler is ecologically segregated. The reasons for these dispersal patterns are discussed. They do not appear to enhance the availability of food resources. It seems more likely that territorial spacing might function to reduce nest predation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00634604
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  • 6
    Electronic Resource
    Electronic Resource
    The seasonal development of photoperiodic responsiveness in an equatorial migrant, the garden warblerSylvia borin (1988)
    Springer
    Journal of comparative physiology 162 (1988), S. 389-396 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Garden warblers (Sylvia borin) are migrating European passerines that spend the winter in tropical Africa. To investigate how photoperiod controls the annual cycles of reproduction, molt and migration, garden warblers were exposed to photoperiodic changes simulating those experienced by conspecifics with an equatorial wintering area. At three different times groups of birds were moved from a constant equatorial photoperiod of 12.8 h to a 15-h photoperiod: group 1 on November 19, group 2 on February 24, and group 3 on April 12. In all birds the changes in body weight, nocturnal migratory restlessness, testicular width or diameter of the largest oocyte, and plasma LH concentrations were determined. In addition, the birds were examined for molt. In all birds of groups 2 and 3 the transfer to long photoperiods induced a gonadal cycle associated with ‘spring’ migratory restlessness and, in the group 3 birds, an increase in LH. In group 1 only few birds showed marginal gonadal responses and the gonadal cycles of the group 2 birds were less pronounced than those of group 3. The results suggest that the hypothalamo-pituitary-gonadal axis was refractory to stimulation by long photoperiods in autumn but, later in the season, became responsive to the same long photoperiods. Unlike the situation in other temperate zone birds, the transition from the photorefractory to the photosensitive state seems to be a gradual process which develops spontaneously and with the appropriate temporal characteristics in the absence of photoperiodic change.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00606125
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  • 7
    Electronic Resource
    Electronic Resource
    Melatonin and the circadian rhythms of feeding and perch-hopping in the European starling,Sturnus vulgaris (1988)
    Springer
    Journal of comparative physiology 164 (1988), S. 7-14 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The role of melatonin plasma titers in the control of free-running circadian rhythms was investigated in European starlings,Sturnus vulgaris, held in continuous dim light. Simultaneous recordings of plasma melatonin, perch-hopping and feeding activity revealed synchronous circadian variations in all three functions with high melatonin titers during resting and low titers during activity periods. Implanting birds with melatonin silastic capsules resulted in a 100-fold increase in plasma concentrations and an abolition of the endogenous melatonin rhythm. Feeding rhythms persisted during this treatment, although the activity time (α) was lengthened and the circadian period (τ) shortened. Similar changes were found in perchhopping activity, but in some birds, this activity was more or less suppressed. These data demonstrate that although melatonin plasma titers freerun synchronously with other circadian parameters, fluctuations in peripheral melatonin are not essential for the expression of circadian activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00612712
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  • 8
    Electronic Resource
    Electronic Resource
    Food exploitation by a winter flock of greylag geese: behavioral dynamics, competition and social status (1993)
    Springer
    Behavioral ecology and sociobiology 33 (1993), S. 289-295 
    Details
    ISSN: 1432-0762
    Keywords: Anser anser ; Groups ; Social interactions ; Strategies ; Parent-offspring
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary To investigate the dynamics of the winter flock patch exploitation, feeding experiments were performed with 140 semi-tame, free-roaming greylag geese (Anser anser). Three different initial densities of barley were offered on a 50-m2 patch: low (1600 grains/m2), intermediate (3300/m2) and high (I 1500/m2). Goose numbers on the patch, peck rates, and frequencies of agonistic encounters and of alert postures were observed by scanning the flock and in focal individuals. At low and intermediate initial food densities, peck rates decreased with food density, whereas at high food density, peck rates decreased only slightly over the feeding bout. Agonistic interactions increased as food decreased. A switch from exploitation to interference competition occurred at a threshold of approximately 900 remaining grains per square meter. With high initial food density, agonistic encounters began to increase gradually after 20–30 min. The same general patterns were observed for frequency of alertness. Family members occupied the patch for the longest time periods. The family female and the offspring fed most intensely. The family gander however, fed significantly less but was more aggressive and vigilant than all other social categories. Solitary geese spent their time on the patch doing little else but feeding and were the first to leave. It seems that high-ranking families and low-ranking singles adopt different competitive strategies, the former being superior interference competitors whereas the latter are forced scramble competitors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00172926
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  • 9
    Electronic Resource
    Electronic Resource
    Seasonal reproduction, moult and their endocrine correlates in two tropical Ploceidae species (1986)
    Springer
    Journal of comparative physiology 156 (1986), S. 641-647 
    Details
    ISSN: 1432-136X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Populations of Reichenow's weavers and rufous sparrows living at the equator were investigated and compared for seasonality in breeding, moulting and fluctuations in the plasma titers of LH, testosterone (in males) and estradiol (in females). These species did not breed during the dry season and they commenced breeding at the onset of the heavy rains (April). In both species, the change from the dry season to the rainy season was accompanied by dramatic increases in gonadal size and steroidogenesis. Surprisingly, plasma titers of the hypophysial hormone LH were not affected. Differences were found in the length of the breeding season: in the weavers it was terminated in September whereas the sparrows bred through January, the end of the study. The differences between the two species in the absence of a pronounced dry season are assumed to be related to the sparrow's ability to interrupt moult and renest in fall when environmental conditions are favourable. in the weavers, no differences in the seasonal changes in gonadal size and plasma titers of LH, T (males) and E2 (females) were found between ‘wet’ and ‘dry’ post-heavy rain periods (October–January) whereas differences were found in the sparrows.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00692741
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  • 10
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    Territorial spacing and interspecific competition in three species of reed warblers (1991)
    Springer
    Details
    Publication Date: 1991-01-01
    Print ISSN: 0029-8549
    Electronic ISSN: 1432-1939
    Topics: Biology
    Published by Springer
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