Where two subspecies meet: Origin, habitat choice and niche segregation of Cormorant Phalacrocorax c. carbo and P. c. sinensis in the common wintering area France, in relation to breeding isolation in Europe.

Great Cormorant (Phalacrocorax carbo) Science Article 24

abstract

The wintering population of Cormorants Phalacrocorax carbo in France reached 66000 birds in January 1992 against 14 000 in 1983. This increase largely concerned the inland areas (holding 55% of the population instead of 28% in 1983). The most important area is the Loire Valley. Analysis of 704 new recoveries or sightings of individually marked birds since 1983 confirms the segregation of habitat between the two races, 84% of sinensis birds being controlled or recovered in inland areas and 80% of carbo birds at sea. The same difference is observed between the French birds from inland and coastal colonies (16% and 97% of ringing sightings or recoveries at sea). In spite of the colour-marking of 22 600 birds among all European breeding areas in the 1980s, only few proofs of exchange of breeders between countries occurred until 1993 (0.3% of Dutch or Danish birds), with a total of 13 birds concerning Denmark, Germany, The Netherlands, France and Ireland, all of them within each race’s breeding area. The new inland tree-nesting colonies in France and East Anglia (England) seem to concern sinensis incursions in vacant breeding carbo area. This juxtaposition of the two races, based on ecological segregation, is discussed.

Marion L., ARDEA 83 (1): 103-114

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