Seasonal variation in the whistles of starling Sturnus vulgaris
Résumé
Observations of sedentary male Starlings at two sites in Brittany from December 1979 to December 1980 showed that the amount of whistled song varies during the year, principally from March to July during the reproductive season. Whistles are not numerous in summer but increase from September. These results suggest a link between whistled songs and testosterone titers. The different whistle types present different evolutions of their relative frequencies. Some are abundant during the nest building phase, others during the feeding phase. The curves were similar at the two sites for a given theme, showing that each theme constitutes an entity and that the different themes are influenced differently by environmental factors. The significance to the learning process in young birds is discussed.