De fabel van de Buizerd, de Torenvalk en de Regenworm

In the polders of Zuidelijk and Oostelijk Flevoland Common Buzzards and Kestrels commonly exploit earthworms in winter. Measurements and weights of three earthworm-eating firstwinter Common Buzzards are given. Their mean body mass of 787 g was almost similar to the average body mass of 793 g of 53 Common Buzzards captured in winter in the same area (minimum of 585 g, maximum of 1040 g), indicating that earthworms can be a sustainable food source. Common Buzzards are probably more adept in exploiting earthworms than Kestrels. A Kestrel was seen to search and strike from poles (six worms in 5 min), whereas a Common Buzzard walked through the meadows and picked up earthworms in passing (35 worms in 5 min, same spot and date as the Kestrel). It is suggested that worm-eating does not affect the condition of Common Buzzards and Kestrels negatively, contrary to common belief.