Drie broedgevallen van Rode Wouwen Milvus milvus in Drenthe in 2018
De Takkeling , Volume 27 - Issue 2 p. 117- 137
At three localities in SW-Drenthe, from March through October 2018, the behaviour of breeding Red Kites and the progress of the breeding cycle were monitored from a distance. Moulted flight feathers, plucks and pellets were collected at the breeding sites. On 5 June nine nestlings, three in every nest, were ringed and their age calculated from the maximum wing chord of the oldest young. Laying date of first eggs were calculated as 3, 4 and 6 April, with hatching date 18 May in all three cases. All nine juveniles left the nesting sites between 13-29 July, when 67-80 days of age. At the nest site Wilhelminaoord the parents left six days before fledging of the young. At the sites De Wijk and Zuidwolde (one of the) parents were observed till 20 September and 11 October respectively. Observations during the day-light period at the site Wilhelminaoord in 16 June-17 July revealed that adults stayed at the nest site, often preening, till 6h15-7h50. The first adult with food arrived 85-186 minutes later. Between 4h20 and 22h20 on average once per 148 minutes an adult arrived with food, approximately 7.3 times per day (n=29) and for the period 9h00-18h00, when adults actually supplied food, 14.2 times per day. Frequency of food-calling was distinctive per nest, low in Wilhelminaoord (once per 23.5 min) and high in De Wijk (once per 11.3 seconds). In plucks, preys and pellets the remains of at least 39 different animal species were found. The share of birds was 49% (n=87 mainly in plucks), mammals 43% (n=74 mainly in pellets) and fish 6%. Red Kites predominantly were seen feeding in agricultural grassland, natural landscapes and along highways. The share in the latter two is relative high. Grasslands were especially frequented during mowing and the processing of cut grass. According to observations of moulting adults and collected primaries 1 to 9 (n=28) and tail feathers 1 to 6 (n=12), moulting of primaries took place between 12 April and 20 September and rectrices between 18 June and 5 September. Primaries 5-6 were moulted by the time the young fledged and shortly thereafter moulting of tail feathers commenced. Timing of the moult of primaries and rectrices in 2018 was on average 14-17 days ahead of the mean dates mentioned in Brune (2001).
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