Summary: Der Ornithologische Beobachter 101: 1924 (2004) 19
Bestand und Verpaarungsstatus von Nachtigallen Luscinia
megarhynchos im elsässischen Rheintal bei Basel
Valentin Amrhein und Daniel Zwygart
Population size and mating status of Rufous Nightingales Luscinia megarhynchos in the Upper Rhine
Valley near Basel. In 2003, we censused singing Rufous Nightingales in a study area of 17.9 km2 between
Saint-Louis and Kembs-Loechlé (France). Three surveys were made during the day and one at night. We
counted 194 singing males, 83 of which were heard only during the day, 38 only at night, and 73 bothat day
and night. Since male Nightingales usually stop singing at night after pairing, we suggest that the 111 noctur-
nal singers were mostly unpaired males, while the minimum number of paired males would be 83. However,
Nightingales were less easily heard during the day than at night. Based on the results from an intensively ex-
amined part of the study area (the Petite Camargue Alsacienne), we assume that the actual number of paired
males was higher than 83 and that the population size was up to 240 males, about half of them being unpaired.
We suggest that the high proportion of unpaired males reflects a strongly male-biased adult sex ratio and dis-
cuss implications for sexual selection and the interpretation of bird census data.
Key words: Luscinia megarhynchos, population size, mating status, bird census, Upper Rhine Valley.
Valentin Amrhein, Forschungsstation Petite Camargue Alsacienne (Universität Basel), Rue de la Piscicul-
ture, F 68300 Saint-Louis, e-mail firstname.lastname@example.org; Daniel Zwygart, Gymnasium Liestal, Friedens-
strasse 20, CH 4410 Liestal, email@example.com
Die Anwesenheit männlicher Nachtigallen ist