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Aves, 39/2 | 2002 | 65-84

  Breeding and wintering of Coots (Fulica atra) on sewage ponds of Hesbaye close to Liège (Belgium)
Jortay, A.

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Our observations of Coot's breeding in sewage ponds of Hesbaye area close to Liège (Belgium) result in estimates of 2.26 +/ - 0;09 youngs hatched per territorial pair, a rate of fledged/ hatched youngs of 64 %, of 1.51 +/ - 0.29 youngs fledged by territorial pair, and of 2.3 % rate of second brood. Those two latter rates are low and could be linked to low food supply. The breeding population has tripled in two years (1997 to 1999), to stabilize around 30 to 40 pairs. This increase follows an increase of water levels, in relation with the agro-industrial activity and abundant winter rains and was made possible by an abundant external income of breeding pairs. 1999 is an exceptional breeding year with a total output of 100 fledglings. The year 2000 presents the highest level of non-territorial coots, suggesting that they may be the surviving juveniles of the year 1999. From 1995 to 2000 the average number of winter coots has been multiplied by factors of 20 to 60. The number of wintering coots was very low in the beginning. Now, the average number of wintering birds fluctuates between a quarter of and the whole breeding local population, depending on the site. This can be explained by a more important level of competition for territories. The Hollogne site seems to be the only one with moulting flocks and wintering there is more frequent. The fast reestablishment of the wintering population following a short period of hard frost suggests that birds could find shelter not far from the concerned sites and the river Meuse (17-30 Km) could be that shelter. More information should be obtained about the links between global evolution of coots numbers and their local breeding, the local exchanges between the different sites in the area and the impact of differences in breeding success between the sites on the population dynamics.

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