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  • 1970-1974  (4)
Material
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 83 (1973), S. 93-102 
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Beginning from fledging time up to the time of homing experiments, 33 experimental pigeons were kept alternatively for three days in a wire-netting aviary which they could leave for spontaneous flights (O-aviary), and for three days in a closed aviary fenced with plastic sheeting (C-aviary). In the O-aviary they wore masks which prevented or limited their breathing through the nostrils. As controls, 31 birds were kept for three days in the O-aviary without masks and for three days in the C-aviary wearing masks. In eight releases from places situated between 10 and 61 km from the aviary, the experimental birds gave worse homing performances than the control birds. Besides, contrary to the control birds, the initial orientation is mostly either wrong or at random in the experimental ones. These results support the hypothesis of olfactory navigation (Papiet al., 1972), which supposes that the pigeons, during their first months of life, gather information on smells prevailing in surrounding regions through the winds.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 73 (1971), S. 317-338 
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The initial orientation of pigeons with various degrees of homing experience was investigated in releases over the sea. The collected data encompasses 22 releases in which a total of 160 pigeons were used and 415 vanishing points recorded. The experiments are grouped into three series: 1. Five groups of young pigeons without homing experience were released over the sea NE, S, and WNW of the loft, situated at S. Piero a Grado near Pisa. Mean directions taken by the birds were between W and NNW (Pigs. 1, 2). In at least four cases the choice seems to be the result of a compromise between a strong directional tendency and a homeward tendency. 2. Young pigeons housed in a loft situated on the coast of the Isle of Capraia and released over the sea at a short distance gave evidence of an orientation influenced by the sight of the island. The pigeons were later divided into two groups and released at 30 km S and 76 km N (Fig. 3); distributions of vanishing points were not significantly different from each other. 3. Two groups of adult pigeons, housed in the loft of S. Piero a Grado and directionally trained on two opposite lines along the coast, were later released from four different points over the sea. All mean directions lead approximately inland and are very close to one another. They do not seem to be affected by the differences in home direction. No deviations between the two groups as predictable on the basis of their training were observed while such deviations are seen to occur in two releases from an overland point (Fig. 6). The orientation over the sea was not guided by direct sensory contact with the land, since birds whose clock had been shifted six hours forward took a course parallel to the coast (Fig. 9). It is tentatively assumed that the birds orientated towards the land by means of a sun-compass mechanism assuming a perpendicular direction to the stretch of the coast with which they had become familiar during their training flights.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 83 (1973), S. 81-92 
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Pigeons not experienced in homing and subjected to olfactory nerve section are generally found to be unable to home from short distances. In nine successive releases from different localities at 3.3 to 11.8 km from the loft, 15 out of 19 experimental birds were lost as well as 2 out of 40 control birds. The homing capacity improves when the birds are released from familiar localities on a line along which they have been trained before undergoing nerve section, but they still perform very poorly in later releases from unfamiliar localities outside the training line. 11 experimental birds showed fairly good performances from a familiar locality on the training line at 43.4 km from the loft (10 returned within the same day of the release, at an average speed of 32 km/h). Only one of these birds was able to home within the same day in a later release in an unfamiliar locality outside the training line at 34.9 km from the loft. Five other birds of this group homed one or more days later, and the remaining five were lost. The initial orientation was poorer amongst the experimental birds. More of the inexperienced experimentals landed near the release point. As the experiments show that olfactory nerve section causes no disturbances in general behaviour and homing drive, it is concluded that olfaction plays an important and specific role in the homing mechanism of pigeons.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 7 (1971), S. 356-360 
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary By producing subitaneous eggs the rhabdocoel Mesostoma ehrenbergii may quickly increase the population size. The production of this kind of eggs by young worms is inhibited by the presence of adults in the culture medium. The inhibition is specific, and it is observed also if young and adult worms are not in direct contact, or if young worms are added to the water where adults had been previously kept: there is therefore evidence for a chemical mediator. The sensitivity to the inhibition occurs during the first five days after birth, with a maximum on the 2nd to 3rd day.
    Type of Medium: Electronic Resource
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