Owls’ hoards rot

For predators, climate change-induced shifts in prey numbers, behaviours and spatial or temporal locations can be a major threat to food security. For predators that hoard prey to ensure survival through harsh winters, climate variation can have a doubled effect — influencing both food capture and store stability. Although northern latitude autumn and winter temperatures have increased dramatically in recent years, the effects of climate on foraging and storing throughout winter remain understudied.

Giulia Masoero at the University of Turku, Finland, and colleagues analysed the impact of climate on Eurasian pygmy owl (Glaucidium passerinum) food-hoarding behaviour across 16 years. They found increased freeze–thaw frequency, lower winter precipitation and deeper snow cover were linked to greater hoard consumption. Higher autumn precipitation and an early hoarding start led to food rot, which reduced female owl recapture (indicating death or emigration).

Although owls delayed hoarding in autumns with fewer freeze–thaw events, suggesting some potential for climate change adaptation, the study indicates that altered climates can decrease owl overwinter survival, which may in turn have vast impacts on the boreal food web.