Individual study: Supplementary feeding appears to promote early laying and larger clutch sizes in European kestrels Falco tinnunculus in the Netherlands
Dijkstra C., Vuursteen L., Daan S. & Masman D. (1982) Clutch size and laying date in the kestrel Falco tinnunculus: effect of supplementary food. Ibis, 124, 210-213
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Provide supplementary food for raptors to increase reproductive success
A replicated controlled trial near wetlands in the northern Netherlands in 1978-80 (Dijkstra et al. 1982) found that European kestrel Falco tinnunculus pairs that were provided with supplementary food initiated clutches earlier and laid larger clutches than control (unfed) pairs in two out of three years (six fed pairs started laying on 6-17th April, average of 5.0-5.7 eggs/clutch vs. 8-10th May and 4.5-4.6 eggs/clutch for 30 controls). In 1980, the differences were far smaller (23rd April and 6 eggs/clutch for three fed pairs vs. 25th April and 5.6 eggs/clutch for 18 controls), possibly due to it being a peak vole year. Significance levels were not provided. Supplementary feeding consisted of 100-120 g of mouse meat every daily (approximately twice the daily needs of captive kestrels), provided from late January (1978) or early March (1979 and 1980) until the start of incubation in late April or early May.