Climate change and perishable food hoards of an avian predator: Is the freezer still working?

Abstract

Changing climate can modify predator–prey interactions and induce declines or local extinctions of species due to reductions in food availability. Species hoarding perishable food for overwinter survival, like predators, are predicted to be particularly susceptible to increasing temperatures. We analysed the influence of autumn and winter weather, and abundance of main prey (voles), on the food‐hoarding behaviour of a generalist predator, the Eurasian pygmy owl (Glaucidium passerinum), across 16 years in Finland. Fewer freeze–thaw events in early autumn delayed the initiation of food hoarding. Pygmy owls consumed more hoarded food with more frequent freeze–thaw events and deeper snow cover in autumn and in winter, and lower precipitation in winter. In autumn, the rotting of food hoards increased with precipitation. Hoards already present in early autumn were much more likely to rot than the ones initiated in late autumn. Rotten food hoards were used more in years of low food abundance than in years of high food abundance. Having rotten food hoards in autumn resulted in a lower future recapture probability of female owls. These results indicate that pygmy owls might be partly able to adapt to climate change by delaying food hoarding, but changes in the snow cover, precipitation and frequency of freeze–thaw events might impair their foraging and ultimately decrease local overwinter survival. Long‐term trends and future predictions, therefore, suggest that impacts of climate change on wintering food‐hoarding species could be substantial, because their ‘freezers’ may no longer work properly. Altered usability and poorer quality of hoarded food may further modify the foraging needs of food‐hoarding predators and thus their overall predation pressure on prey species. This raises concerns about the impacts of climate change on boreal food webs, in which ecological interactions have evolved under cold winter conditions.

Estimating the long-term repeatability of food-hoarding behaviours in an avian predator

“…Among-individual variation in food-hoarding behaviours is likely owing to consistent differences in how individuals cope with risks and therefore may reflect different individual strategies to buffer against starvation risks. Recent research showed that climate change can lower food store quality [11], prey abundance [56,57] and cause higher uncertainty in environmental conditions, thus potentially impacting pygmy owls’ fitness and population dynamics in the long-term. Whether repeatable variation in food-hoarding behaviours can facilitate pygmy owls' persistence and adaptation to climate changes remains to be investigated.…”

“…The optimal food-hoarding strategy is hence likely determined by trade-offs between risks and benefits and may shift among and within individuals. Indeed, previous research showed that food-hoarding behaviours can covary with environmental factors [10,11] and differ between sexes and age classes [12,13], while variation in food-hoarding behaviours was also shown to associate with survival, breeding success [11,14] and sexual selection [15]. Importantly, among-individual variation in food-hoarding behaviours may capture intrinsic tendencies of individuals to be more risk-prone or risk-averse and to minimize the potential consequences of uncertainty [16].…”

Frozen out: unanswered questions about winter biology

“…Leveraging the growing number of published studies investigating how winter influences populations can provide insight into broader trends of the mechanisms by which events in winter influence populations and how interspecies variability in life history traits may influence their susceptibility to the effects of winter (Question 24; Altwegg et al 2005). Abiotic winter conditions are a potentially important selective filter, but variation in the behavioural and D r a f t physiological responses of individuals to these harsh abiotic conditions can also buffer or magnify the effects of these conditions on populations (Leirs et al 1997;Coulson et al 2002;Uelman Jr et al 2016;Froy et al 2019;Masoero et al 2020). Broader life-history characteristics, such as life span (Saether and Bakke 2000), overwintering strategy (e.g.…”

Flight capacity drives circadian patterns of metabolic rate and alters resource dynamics

“…Thus, I used the variable field cricket ( G. lineaticeps ) to examine the role of flight capacity in (1) circadian patterns of SMR, (2) food consumption, and (3) efficiency by which ingested food is converted to somatic and reproductive tissues. Careful examination of the role of life‐history strategy in circadian patterns of resource use, as well as in resource acquisition and allocation, may inform drivers of life‐history evolution given the increasing uncertainty of food availability in many global regions (Ciais et al, 2005; Currano et al, 2008; Masoero et al, 2020).…”