Webcamobservaties bij het nest van een Torenvalk Falco tinnunculus in 2008

The breeding behaviour of a Kestrel pair, breeding in a small nestbox, was observed with two webcams, one in the box itself, another focused on the plank in front of the entrance. Observations started on 19March 2008. The first egg was laid on 17 April, and every other day another egg was added until the clutch was completed on 27 April. During egg laying the female’s presence in the nextbox increased from 2 hours per day till 11 hours by the time the clutch was completed (excluding the night). The first four eggs hatched on 23 May, followed by the 5th and 6th egg on 24 and 25 May, respectively. The frequency of shifts during incubation decreased from 27 times per day at first, to 7 times per day just before hatching. Female shifts averaged 38 minutes early in the incubation period, to increase to 200 minutes prior to hatching (maximum of 230 min); at the same time the female’s share in incubation (excluding the night) increased from 493 to 843 minutes. Conversely, male shifts declined from 39 to 9 minutes on average (maximum of 92 min), and his daily incubation effort declined from 352 to 27 minutes. Just before hatching, his hunting efforts substantially increased instead. During the first nine days after hatching, the female stayed in the nestbox most of the time. She partitioned the prey brought by the male (which took 6 minutes per vole), and fed the chicks. The chicks were seen tearing apart prey by themselves on their 12th day of life. From then on, the female increasingly spent time outside the nestbox (partly to hunt): during the first week of life, the chicks were unattended by the female for on average only 46 minutes per day, but this already increased to 700 minutes per day after the second week. The number of prey delivered to the nest increased twofold in the first week after hatching (from 7 to 15 voles, on average 1.2-2.5 voles/chick), then slightly increased to 17 voles/day in the second week and to 27 voles/day in the third week; from then on, prey delivery remained more or less stable (in terms of biomass: 80-100 g per day). The main prey species was the Common Vole Microtus arvalis, with 90% of all prey items (91% in biomass). The first chick fledged prematurely when 29 days old, as it was accidentally pushed off the plank in front of the nestbox by the prey-delivering male. Another fledged when 30 days old, and all six juveniles had fledged some days later.