Autumn freeze-thaw events carry over to depress late-winter reproductive performance in Canada jays

Abstract

Evidence suggests that range-edge populations are highly vulnerable to the impacts of climate change, but few studies have examined the specific mechanisms that are driving observed declines. Species that store perishable food for extended periods of time may be particularly susceptible to environmental change because shifts in climatic conditions could accelerate the natural degradation of their cached food. Here, we use 40 years of breeding data from a marked population of Canada jays ( Perisoreus canadensis ) located at the southern edge of their range in Algonquin Provincial Park, Ontario, to examine whether climatic conditions prior to breeding carry over to influence reproductive performance. We found that multiple measures of Canada jay reproductive performance (brood size, nest success and nestling condition) in the late winter were negatively correlated with the number of freeze–thaw events the previous autumn. Our results suggest that freeze–thaw events have a significant detrimental impact on the quality and/or quantity of cached food available to Canada jays. Future increases in such events, caused by climate change, could pose a serious threat to Canada jays and other food caching species that store perishable foods for long periods of time.

Raising young with limited resources: supplementation improves body condition and advances fledging of Canada Jays

“…The hoard-rot hypothesis, proposed to explain the > 50% decline in the Canada Jay population observed since the 1980s, suggests that cached food degrades more quickly with warmer fall conditions, resulting in a reduction of the food available to support the late-winter nesting of Canada Jays (Waite and Strickland 2006). While there has been some support for this hypothesis (Sechley et al 2015, Whelan et al 2017, Sutton et al 2019, we did not detect a decline in nestling body mass, body size, or body condition over the past 40 yr. It is possible that breeding pairs will only continue with a nesting attempt if their cached food stores remain above a certain threshold.…”

Simple signals indicate which period of the annual cycle drives declines in seasonal populations

“…The need to identify the period of the annual cycle that is driving population declines is particularly pertinent to migratory species whose seasonal habitats are often separated by vast geographic distances and whose populations have experienced ongoing global declines (Wilcove & Wikelski 2008;Young et al 2016;Ceballos et al 2017). Several recent examples have demonstrated the insights gained from integrating information across the annual cycle to understand how changes in the environment drive population dynamics, both in the wild (Norris & Marra 2006;Luis et al 2010;Ferreira et al 2016;Woodworth et al 2017;Sutton et al 2019) and in experimental populations (Betini et al 2013a(Betini et al , 2014(Betini et al , 2017. Knowledge of when and where populations are limited has important implications for the targeting of conservation efforts and funding (Sheehy et al 2011).…”

Environmental conditions modulate compensatory effects of site dependence in a food‐caching passerine

“…Given this critical dependence on perishable cached food items, two factors have been proposed as being especially important for Canada Jay survival and reproductive success. The first is a consistent, below‐freezing winter temperature regime, which is supported by evidence indicating that Canada Jay reproductive performance is greater following falls and winters of lower than normal temperatures and/or numbers of fall freeze‐thaw events (Waite and Strickland 2006, Sutton et al 2019, in press ). The second is the availability and quality of storage sites that preserve cached food over time.…”