Temperaturabhängiger Brutbeginn, Pflanzenphänologie und Zweitbrutanteil bei der Wasseramsel Cinclus cinclus.
(von 1994 bis 2006 vergeben)
Brutbiologie, Brutperiode, Schlüpfdatum, Phänologie, Lufttemperatur, Wassertemperatur, Beringung, Blütezeit
Schweiz, Zürichsee, Sihl, Wehrenbach, Küsnachter Bach
Spring temperature, plant development, hatching date and frequency of second clutches in the White-throated Dipper Cinclus cinclus. In the 21 years from 1992 to 2012 breeding data of White-throated Dippers were collected in the region of Zurich on the Swiss Plateau, at an altitude of 410 to 680 m a.s.l. The colour-ringed populations of three rivers with a length of 22 km (27 breeding pairs), 7 km (13 bp) and 6 km (7 bp on average) were observed year-round with special effort in spring. Out of 1341 broods a total of 3848 nestlings were ringed at the age of 9–13 days. 876 (65.3 %) of all successful broods were first, 465 (34.7 %) second broods. The yearly hatching dates of first broods were compared with the mean air and water temperature in January, February and March in the corresponding year. Furthermore phytophenological data were analysed, i.e. onset of full flowering for Coltsfoot Tussilago farfara, Wood Anemone Anemone nemorosa, Cuckoo Flower Cardamine pratensis and Dandelion Taraxacum officinale, the date at onset of flowering for Cherry tree Prunus avium, and the date at onset of foliation for Common Hazel Corylus avellana, Horse Chestnut Aesculus hippocastanum, European Rowan Sorbus aucuparia, Weeping Birch Betula pendula and Common Beech Fagus sylvatica (air temperature and phytophenological data provided by MeteoSwiss). The median hatching date of first broods was correlated significantly with mean air and water temperatures in February (Spearman rank correlation, p<0.001 both), whereas in January or March there was only a weak or no correlation. In particular, the onset of flowering of all 4 field flowers analysed was correlated significantly (p<0.001, p<0.05 resp.) with the Dippers hatching date, as well as the onset of flowering in the Cherry tree and the onset of foliage of 4 out of the 5 bush and tree plant species. Finally, hatching date of the first broods predicted a precocious or delayed flowering or leaf growth for many plant species. As a principle, air temperature in February influences water temperature and determines the reproduction of Dippers: The proportion of second broods is correlated significantly (p<0.02) with the hatching date of first broods. And, due to the great variability of this date, the proportion of second broods was varying from 20.0 % to 43.4 % per year.
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