Reptielen als voer voor jonge Buizerds Buteo buteo

In The Netherlands, reptiles are routinely taken as food by Buzzards during the breeding season, although their proportion in the summer diet differs strongly between years, between regions and between pairs. On the Veluwe, the dry-sandy central Netherlands, reptiles were much less commonly taken (2 Vipera berus and 40 Anguis fragilis among 2603 prey remains between 1974 and 2012, i.e. 1.8%) than in Drenthe, where heathlands and forests are interspersed with brooks and fens (11 Vipera berus, 46 Anguis fragilis and 62 Natrix natrix among 3907 prey remains between 1984 and 2011, i.e. 3.0%). In 2012, snakes and slow worms were even more commonly taken as prey by Buzzards in Drenthe: 32 among 114 prey remains found on 25 nests with 81 nest visits in total. Of these reptiles, all vipers, 6 out of 8 slow worms and 13 out of 16 grass snakes were found on a single nest (with 30 of the 81 nest visits in 2012), situated in the border zone of woodland and heathland (partly wet). This area, Wapserveld, harbours a rather high density of reptiles. Fixed transects (partly outfitted with refuges), carried out by Bastiaan Walpot and Maryan Verver, produced sightings of 3684 reptiles in 2004-10, mostly vipers (37.7%) but also viviparous lizards Zootoca vivipara (26.9%), slow worms (20.3%, almost exclusively beneath refuges) and grass snakes 15.1%). Numerical nor relative abundance, however, could be determined, as reptiles were not individually marked. Similarly, abundance nor accessibility of other prey species, notably small mammals and birds, are known for this region, and hence any reference to this Buzzard pair having a specialised diet (or not) is out of the question. In fact, it is likely that the specific conditions of spring 2012 favoured preying on reptiles, as long periods of inclement weather were interspersed with short sunny episodes, influencing basking behaviour of reptiles. In terms of biomass, slow worms are of minor importance in the diet of Buzzards; the mass of captured males averaged 9.0 g (N=20, SD=2.32, range 1.5-13.0 g, excluding a male that was probably misidentified, and must have been a female), of females 18.7 g (N=11, SD=4,30, range 13.1-26.6 g). Snakes were a bit more profitable to capture. Average mass of vipers taken as prey was 53.3 g (N=3, SD=13.9, range 34-66 g), of grass snakes 115.7 g (N=10, SD=52.6, range 64-219 g). In the summer diet of Buzzards, as found on Veluwe (1974-2012, N=2603) and in Drenthe (1984- 2012, N=4021), the top three constitutes rabbits Oryctolagus cuniculus (although the population of this species has crashed, and rabbits have become rare Buzzard prey in my study plots), nestling carrion crows Corvus corone and moles Talpa europaea (together 49.8% of total biomass; Appendix 1).