Prey delivery and diet of the Eurasian kestrel (Falco tinnunculus) in a peak year of the wood lemming (Myopus schisticolor)

Abstract

I used video monitoring to study diet and prey delivery rate of six breeding pairs of the Eurasian kestrel (Falco tinnunculus) in Trysil, south eastern Norway, during the breeding season 2011. A total of 284 prey items of 9 species were recorded delivered at the kestrel nests. The abundance of small mammals was estimated in each kestrel territory. Voles were the most abundant prey delivered at the nests. The kestrels showed a functional response to Microtus voles (Field vole (Microtus agrestis) and Root vole (Microtus oeconomus) pooled), but not to bank vole or wood lemming. This suggests that Microtus voles were preferred prey for the kestrels. Wood lemming was an alternative prey to Microtus voles, while bank vole had a negative, but insignificant trend. Birds or common lizard was not alternative prey to Microtus voles. Studies on predation on wood lemming by kestrels are rare, and I suggest that wood lemmings are caught only when the abundance of wood lemming is high and the abundance of Microtus voles is low. Common lizard were more frequently delivered between 9 am and 1 pm, and the probability of a bird being delivered at kestrel nests increased with solar height. The probability that a prey delivered at the nest was a wood lemming increased throughout the day, and was twice as high in the evening than in the morning. This may suggest that the wood lemming is more active in the evening and therefore more vulnerable to hunting kestrels, or may be mistaken for a Microtus vole as the daylight fades away.