Predation of boreal owl nests by pine martens in the boreal forest does not vary as predicted by the alternative prey hypothesis
Auteur : Sonerud (Geir A)
Année de publication : 2022
Publication : Oecologia
Volume :
198
Fascicule : 6
Pagination : 995-1009
Résumé :
The alternative prey hypothesis (APH) states that temporally synchronous population fluctuations of microtine rodents andother small herbivores are caused by generalist predators that show functional and numerical responses to the abundanceof microtines. This would lead to an increased predation of alternative prey in the low phase of the microtine populationfluctuations. One candidate for such a predator is the tree-climbing pine marten (Martes martes), which includes bird eggsin its diet, among them eggs of the cavity-nesting boreal owl (Aegolius funereus). I used long-term data to test whether pine marten predation of boreal owl eggs in nest boxes varied as predicted by the APH. The probability of predation of owl nestssituated < 45 km from a site where microtines were trapped in spring during four decades increased with microtine trap-ping index, which is opposite to the prediction from the APH. As the data set was limited to one nest per box, I extended itspatially and temporally using the clutch size of each boreal owl nest as a proxy for the actual microtine abundance at thesite. The probability of nest predation increased with clutch size. However, the effects of microtine index and owl clutchsize became non-significant when I controlled for habitat, and in particular cavity age, which had an overriding effect. Theincrease in predation probability with cavity age suggests that the long-term spatial memory of pine marten is an important factor in the pattern of its nest predation in tree cavities.