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  • 1
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Table 1 Genotypes of nest attendants and goslings of four lesser snow goose families DNA marker DQSG1-AI DQSG1-AII DQSG1-CI DQSG5-BI DQSG5-BH DQSG5-BIU DQSG6-AIS DQSG7-BI DQSG7-BII DQSG7-BIII DQSG8-BI DQSG8-BII DQSG8-DI ...
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1939
    Keywords: Clutch size ; Feeding ecology ; Energy budgets ; Pre-breeding period ; Anser caerulescens caerulescens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The potential contribution of early spring feeding conditions in the Arctic to clutch size variation was examined in a population of Lesser Snow Geese Anser caerulescens caerulescens. Behavioural observations were combined with energetic analyses of food material to derive an estimate of the energy budgets of pre-laying and laying females. Food intake of females between arrival on the breeding grounds and incubation was considerable; estimated energy gains in this period were in the same magnitude as the cost of one or several eggs. The pre-laying period spent on the breeding grounds can thus be energetically beneficial rather than costly. Accumulation of resources for reproduction in Snow Geese is a continual process including the breeding grounds, and nutrient limitation after arrival in the Arctic cannot sufficiently explain the environmental component of clutch size variation. The timing of migration and follicle development is such that clutch size decisions are sometimes made during the late stages of migration and some-times after arrival. In the latter case food conditions on the breeding grounds may greatly influence clutch size; in the former case they may still influence readjustments of clutch size after the initial decision. The universal negative correlation between clutch size and laying date in Snow Geese can be explained by negative fitness consequences of late hatching, which outweigh the benefits of delayed laying and further nutrient accumulation. Food shortage on the breeding grounds may sometimes be a secondary factor contributing to seasonal clutch size decline.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 79 (1989), S. 83-90 
    ISSN: 1432-1939
    Keywords: Clutch size ; Laying date ; Lesser Snow Goose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Different mechanisms proposed to explain the intra-seasonal decline in clutch size of Lesser Snow Geese (Anser caerulescens caerulescens) were tested at the La Perouse Bay colony, Manitoba, Canada. Ovary examination of females collected after laying revealed that the actual number of eggs produced per female decreased over the laying period. This finding eliminates nest-parasitism, partial clutch predation and renesting attempts as sufficient explanations for seasonal clutch size decline. Follicular atresia induced by reserve depletion was also rejected since its occurrence was similar among early and late nesters. The decline in clutch size was observed within age-classes, and therefore age effects on clutch size and laying date per se do not account for the observed relationship. Clutch size and laying date were respectively positively and negatively correlated with the amount of nutrient reserves in females at the onset of laying, and also covaried within individuals observed breeding in several seasons. Laying date repeatability was estimated at 0.22. It is postulated that the seasonal decline in clutch size results mainly from a positive feed-back of female's nutrient reserves on the hormones controlling ovary development. Hatching synchrony or shortness of the breeding season may be the ultimate factors responsible for the intra-seasonal clutch size decline in Lesser Snow Geese.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] 'Independent' male ruffs have a territorial breeding strategy of defending lek mating courts against other independents. Non-territorial 'satellites', representing about 16% of males15 (D.B.L. and CMS., unpublished data), move among, are recruited to and share independents' courts7'8'11. ...
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 56 (1983), S. 318-322 
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In many species, fecundity is dependent on age. For some populations — particularly those exploiting temporally variable environments — these age-specific fecundities may themselves vary with time. In this report, we investigate the general effects of age and time on clutch size in a wild population of Lesser Snow Geese (Anser caerulescens caerulescens). We show that both factors affect clutch size independently. Age effects are confined almost exclusively to the two, three and four year old age classes. Mean clutch sizes of all age classes show considerable inter-seasonal variation. These temporal differences in fecundity will ultimately influence the dynamics of the population. In particular, they imply that there will be no convergence to a constant growth rate or a stable age distribution.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of ornithology 135 (1994), S. 355-358 
    ISSN: 1439-0361
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of ornithology 125 (1984), S. 473-477 
    ISSN: 1439-0361
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Summary Eight ♂ and eight ♀ each of the mainland (T. g. castanotis) and the island race (T. g. guttata) were kept together in a large outdoor flight cage (22×8×5 m). Over a two months period, the pattern of pair formation was observed. In this time seven pairs of the mainland and four pairs of the island race were formed. No pair-formation was observed between members of the opposite race even though at the end of the experiment unpaired individuals of only the opposite race were available as potential mates. Social interactions between the races were rare. It can be concluded that under the semi-natural conditions of the experiment the two races of the Zebra Finch behaved like separate species.
    Notes: Zusammenfassung In einem großen Freiflugraum wurden jeweils acht ♂ und acht ♀ der Festlandrasse (Taeniopygia guttata castanotis) und der Inselrasse (T. g. guttata) des Zebrafinken zusammengebracht und die auftretenden Paarbildungen verfolgt. Im Verlauf des mehr als zweimonatigen Versuchs bildeten sich sieben Paare der Festland- und vier Paare der Inselrasse. Mischpaare wurden nicht beobachtet, obwohl am Ende unverpaarte Vögel nur der jeweils anderen Rasse als potentielle Partner zur Verfügung standen. Auch soziale Interaktionen zwischen den Rassen waren selten. Unter den halbnatürlichen Bedingungen des Experiments verhielten sich die beiden Rassen somit wie zwei getrennte Arten.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-4927
    Keywords: isoenzyme status ; electrophoretic genetic variability ; snow goose ; esterases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract A maximum of 22 bands comprising four esterase subgroups—acetylesterase, carboxylesterase, cholinesterase, and acetylcholinesterase—were detected following electrophoresis of lesser snow goose sera on polyacrylamide gels. A minimum of seven structural genes was surmised to be involved in the biosynthesis of these enzymes following physiochemical characterizations. The genetic variability of these loci was calculated to be 1.25% average heterozygosity, while 14.3% of the loci were polymorphic. These estimates of genetic variability were substantially lower than those reported for other vertebrate species. The low degree of genetic variability found in snow goose serum esterases coupled with the extensive protein multiplicity observed may possibly reflect an adaptive strategy based on “biochemical plasticity” rather than genic heterozygosity for this species. The nature of evolutionary forces acting upon multiple enzyme systems such as esterases is discussed. The concept of “conditional neutrality” is introduced and defined within this context.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1573-3297
    Keywords: Drosophila pseudoobscura ; Drosophila persimilis ; phototaxis ; intrapopulation variation ; behavior
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract The photoresponses of natural populations ofD. pseudoobscura andD. persimilis, occurring sympatrically, are measured in two environmental conditions (“at rest” and “disturbed”). Comparisons of the responses, intraspecifically and interspecifically, lead to the following conclusions. These must be considered within the confines of the operational nature of the measurement of laboratory photoresponses. (1) Within each species population, significant nonenvironmental differentiation has been allowed or produced by selection in the “at rest” photoresponse. No significant nonenvironmental differentiation is found in the photoresponse measured in a disturbed condition. (2) Within each species population, a higher mean “disturbed” photoresponse has been favored. The intensities or patterns of selection acting on these two photoresponses have differed such that more intrapopulation differentiation has been allowed or produced in the “at rest” photoresponse. (3) A higher mean photoresponse has been favored inD. persimilis for both conditions. The intensities or patterns of selection acting between these two species populations on the “at rest” photoresponse have differed such that more intrapopulation differentiation has been allowed or produced inD. persimilis. (4) Comparisons of this study with one on intraspecific and interspecific differentiaiton in wing length lead to the conclusion that the selective differences inferred above have acted at a level more specifically attuned to photobehavior.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Behavioral ecology and sociobiology 18 (1986), S. 303-310 
    ISSN: 1432-0762
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Seasonal changes in sex ratios during a 4-year study of red-necked phalaropes and a 3-year study of Wilson's phalaropes showed that females preceded males to breeding and/or courtship areas. The degree to which females preceded males may have been constrained by harsh weather, as the arrival of red-necked phalaropes was synchronous in 1983, when spring was unusually late. Neither sex defended territories; females competed vigorously for direct access to males. These findings show that selection for sexually asynchronous arrival need not act through territoriality. We interpret early female arrival as an adaptation for obtaining mates and coclude that sexual selection may be an important determinant of arrival times in mate defense social systems.
    Type of Medium: Electronic Resource
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