Aves, p�le ornithologique de Natagora

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Aves, 23/1 | 1986 | 22-33

  Autumnal observations of Cormorant (Phalacrocorax carbo) in the Woluwe valley.
WALRAVENS, M.

Article summary

Observation of visible migration in the woluwe valley (Brabant) since 1976 has confirmed the passage of the Cormorant since 1982. The number of flights and birds involved have continued to increase, concordant with the increase of nesting populations of this species in Western Europe. The passage commences timidly with a small flight at the beginning of September, but is essentially concentrated in october and the beginning of November. The average date of passage fluctuates between 12 and 28 October. The end of observations is often very sudden and occurs at the onset of the first cold spell. This is also the time of passage of the Grey Lag Geese (Anser anser). An astonishing correlation was noted between days of passage and week-ends in 1985. The modulation of the passage during the course of the morning comprises essentially two phases : the first, beginning more than half an hour after sunrise, reaches apogee between two and three hours and a half : the flights of which it is comprises most possibly come from Zealand. The second, often consisting of large flights, is short and takes place between four and a half and five hours after sunrise; it probably comes from south Zuiderzee.

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