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Institut de recherche pour la conservation des zones humides méditerranéennes

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Titre :	Common Starling Sturnus vulgaris clutch size, brood size and timing of breeding during 1971-2015 in Southwest Jutland, Denmark
Auteurs :	Peder V. Thellesen, Auteur
Type de document :	Article
Dans :	Dansk Ornitologisk Forenings Tidsskrift (111(3) 2017)
Article en page(s) :	87-95
Résumé :	For 45 years (1971-2015), I have studied the breeding biology of the Starling in Southwest Jutland concentrated on a colony at my dairy farm in Hjortaer (5532 N, 08.43 E), housed in up to 27 nest boxes where birds have been ringed every year (Hjortkaer, PVT; Tab. 1). Detailed studies on egg and nestling production and timing were performed on 1025 nests during 1974-2006 and again in 2015. In addition, Starling nestlings were ringed at four neighbouring farms (Hjortkaer, neighbours) during 1974-2015 and at 27 sites in a larger area of Southwest Jutland (Southwest Jutland, minus Hjortkaer; Tab. 1) during 1975-1998.During the study period, 11 978 nestlings from 2580 broods were ringed. In addition, 22 juveniles and 450 adults were ringed; a total of 12450 Starlings altogether. During 1976-2001 and 2015, 448 adult Starlings were also colour ringed, to identify individuals, identify mates in pairbonds and identify which nest box individuals occupied (Thellesen 2002). Nest box occupancy was more or less 100% until c. 2004, after which it fell to c. 60% (Fig. 1).This decrease coincided with feral cat Fells catus and stone marten Martes foina predation during 2004-2006 (Fig. 5), although the decline has continued following these years.The mean number of eggs in the first clutch was 5.56 +/- 0.035 (+/- SE, range 1-11 eggs; Tab. 1), although the larger clutches (811 eggs) were probably the result of another female egg-dumping in an established female's nest.The mean second clutch size was 4.27 +/- 0.074 (range 2-7; Tab. 1).The mean number of nestlings in the first clutch was 4.83 +/- 0.027 (range 1-10) at the time of ringing, and in the second clutch 3.43 +/- 0.056 (range 1-6 nestlings; Tab. 1).The mean number of eggs per clutch, as well as the mean number of ringed nestlings per clutch, showed no significant change amongst both clutches throughout the study period (Fig. 2). The mean duration of incubation was determined for 202 nests and found to be 11.94 +/- 0.034 days (range 11-14 days; Fig. 3), and mean time to fledging for 150 clutches was 19.89 +/- 0.083 days (range 18-23 days; Fig. 3).The number of Starling pairs initiating a second clutch varied greatly from year to year. Second clutches were found in 25 of the 45 years, but in only 10 years were second clutch eggs found in more than half of all nest boxes (Fig. 1).The mean clutch size in second clutches increased with the number of pairs laying second clutches (Fig. 4). Average breeding success (ratio of young fledged in relation to eggs laid) was 79% amongst first clutches and 62% in second clutches (Fig. 5).The annual first egg dates show that the breeding period has advanced by one day per 5.0 years amongst first clutches (1974-2015) and by one day per 4.7 years amongst second clutches (1977-2015), corresponding to an advanced mean egg laying date of 9.1-9.6 days during 1971-2015. The corresponding ringing date (1971-2015) has advanced by 6.1 days and 8.6 days for first and second clutches, respectively (Fig. 6). Amongst first clutches, the slightly lower rate of change for the eggs is the result of a tendency to ring the chicks at an older stage in recent years after the period of intense predation. There was a significant relationship between the annual mean local temperatures in April and the onset of the breeding period (Fig. 7).

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