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La Tour du Valat

Institut de recherche pour la conservation des zones humides méditerranéennes

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Titre :	Bird-watching and species numbers - a local study based on intensely audio-visual recording. (2010)
Auteurs :	Einhard Bezzel, Auteur
Type de document :	Article
Dans :	Vogelwarte (48(1) FEB 2010)
Article en page(s) :	1-13
Langues:	Allemand
Résumé :	In 1978-1987 122 bird species were recorded by several well trained birdwatchers in daily checks at a study plot of eight ha between mountain forest and gardens in a valley of the Bavarian Alps (Germany) at 811 m asl. with six (596) species present in more than 9996 and 44 (3696) in less than 196 of a total of 730 five days periods For 56 species breeding could be proved The yearly set of species did not change within ten years. In three consecutive years after the study period no new species were recorded at the plot, only single individuals of seven new species flying over the valley. Of the species totals per five days periods 72% could be recorded in the first year, 996 in the second, and approx 196 in each of the years seven to ten The species total of ten years indicates seasonal fluctuations as expected with a maximum of 70 species per five days period in May (11 /15 5.) and minima of 31 in January (1 1 -15 1.) as well as in December (22./26.12) The highest daily maximum was 40 species in May (16 -20 5), the lowest 16 in December (22 -26.12) Species totals of five days periods as well as daily maxima correlate positively with daily medians, increase of species numbers in spring and decrease in autumn were positively related to mean temperatures and negatively to the number of days with complete snow cover. Surprisingly, the number of days necessary for detecting a defined percentage of species totals per five clays periods does not follow a yearly fluctuation All the year round 2596 of the species were recorded in 1.2, 5096 in 3.7, 7596 in 11 1 and 10096 in 43,9 days of bird-watching as an average, which means in the 1(st), 1(st), 3(rd), and 9(th) year, respectively Nevertheless, different detection probability plays an important role in seasonal comparisons of species numbers. Among the five days periods between mid of April and end of July only in nine of 22 all 41 breeding species considered could be detected 5096 of the breeding species were recorded on the first day, 65% on the 3(rd), and 80% on the 6(th) day of bird-watching During summer differences of detection probability according to the state of breeding were evident as well as species specific traits Among the species requiring much time to be recorded during advanced breeding season were Hawfinch, Mistle Thrush, Whitethroat, Marsh Tit, and Spotted Flycatcher The results of intensely long-term bird-watching suggest to improve some methodical proposals widely used so far More than four clays seem to be necessary for thorough checks even on smaller plots and more attention should be paid to the end of breeding season with presumable higher detection probabilities in some species To look into more detailed problems minimum standards proposed for practical purposes should be upgraded Moreover, our findings suggest spending more time in using standardised methods for recording arrival or departure of migrants. Presumably, standardised recording of seasonal sets of species offers alternatives for the birdwatcher tracking effects of climate change

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