Aves, p�le ornithologique de Natagora

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Aves, 57/2 | 2020 | 59-86

  A move between two broods is the answer of Little Grebe Tachybaptus ruficollis to extreme climatic events
Alain Jortay

Article is not available in pdf French article available for download in 2022

Article summary

This work is the result of a 20 years weekly survey of a Little Grebe breeding population (average 20 pairs) in 3 sewage ponds sites of Hesbaye (Belgium). Breeding pairs were allocated to territories; 444 territories were defined and compared in terms of estimated arrival dates. Two waves of incoming birds are described, the first one from February to mid-May, the second one from mid-May to August. The Grebes incoming with the first wave seems to use the same territory during the whole breeding season, but 12 % changed to another pond of the same site and 4 % to a pond of one of the 3 sites. 74 % of these moves can be explained by changes in the ponds water level. The second wave is not observed every year, but some years (2005/2006 and 2011/2012) increase by a factor 2 the usual local breeding population total. Statistical tests with meteorological data from France and southern Belgium were used to test links between Little Grebe moves and rainfall excess or deficit. When Belgian data provided only negative correlations, significant correlations were found for 56 meteorological stations in France (on a total of 96) for 2-3 years long drought. In these extreme climatic event conditions, Little Grebe can be classified as itinerant breeder (Newton, 2008). As the information of breeding period moves of Little Grebe in Europe is very partial, especially including Mediterranean range, and without any satellite ringing program available, we recommend to birdwatchers doing local surveys the approach of a new methodology. This methodology implies the definition of 2 different periods (March / May and May / August) with 5 census in each period, and was successfully tested in our study for a local population of 15 pairs.


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