Vergelijking van de broedcyclus van polygame en monogame Buizerds Buteo buteo

The parental investment of a long-term bigamous Buzzard pair was compared to that of a monogamous pair (in fact, two pairs, as the one covered during the nestling stage was another than the one used for the incubation period), using time-laps webcams. The number of observation hours amounted to resp. 192 h and 174.3 for incubation and nestling stage of the monogamous pairs, and resp. 192.8 h and 129.6 h for ditto stages of the bigamous pair. The cameras were positioned within 1.5-4 m of the nest. Each minute a photograph was taken, with three additional photographs (in 15 sec intervals) per minute in the nestling stage when movement was detected (to allow identification of prey items). Photograps taken between 22.00 and 5.00 h summer time were not used in the analysis. The monogamous pair started laying on 11 April 2014, and clutch size was 3 eggs. During day 7-14 the female’s share in incubation was 91% of the daylight hours, the male’s share 7%; the clutch was not incubated during only 2% of the time. The second monogamous had two chicks, which were monitored from day 4 onwards. The female was on the nest for 81.8% of the observation period, the male for 0.4%, both for 0.1%; during 17% of the time neither parent stayed on the nest. The female’s activities consisted of leisure time (83%), feeding chicks (16%) and preening (1%). Of 61 preys brought to the nest, 95% were provided by the male. Prey consisted of Arvicola amphibius (1), Rattus norvegicus (2), Microtus sp. (18), voles/mice (26) and unidentified (14). The bigamous pair started laying on 9 April 2014, and produced a clutch of 7 eggs (the trio produced 5x 4, 2x 5, 1x 6 and 1x 7 eggs in 2008-16, resulting in 3x 0, 3x 1, 2x 3 and 1x 4 fledglings). During day 24 through 32 of the egg stage, the females were incubating in duo for 51% of the observation time, with another 23% by female A and 25% by female B. The male stayed on the nest for only 0.2% of the time (twice on the same day, for 6 and 13 minutes respectively); the nest was not incubated for 0.11% of the time. This nest produced a single chick. During the nestling period, the females stayed on the nest together for 63% of the time, female A for another 20% and female B for 15%. The nest remained unattended for 2% of the time (that is: within frame of the camera); the male was never seen on the nest during this stage. The female(s) spent 68% of the time preening, 23% in leisure and 9% in feeding the chick. Of 26 preys delivered, 73% were by the male. Prey included 10 mice/voles, 7 Microtus sp., 2 Arvicola amphibius, 2 Apodemus sylvaticus and 2 unidentified.