Exploiting boom times. Southern Boobook OwlNinox novaeseelandiaediet during a rodent irruption in central Australia

Abstract

Populations of Australian desert rodents are known to undergo booms in response to resource pulses following periods of high rainfall. Australia's arid-adapted Tyto owls have been recorded responding functionally and numerically to these small mammal booms, though it is not known whether Southern Boobook Ninox novaeseelandiae is able to respond similarly. We aimed to determine whether Southern Boobooks could find and exploit a localised rodent irruption in the western Simpson Desert, in a location with few roost trees and no tree hollows. Boobook owls immigrated to the site from an estimated distance of ≥ 32 km and appeared to be resident over a period of ≥ 4 months, coinciding with a localised irruption of Plains mice Pseudomys australis. Dietary analysis confirmed that the owls specialised on small mammals, with rodent and dasyurid species accounting for c. 98% of prey items and > 99% of prey biomass. There was no evidence of reproductive activity among the owls and they vacated the area as the small mammal irruption subsided. Although a dietary generalist across its range, our results indicate the Southern Boobook is capable of specialising on small mammals during population irruptions.