Large diurnal temperature range increases bird sensitivity to climate change.

Michael Briga,Simon Verhulst

doi:10.1038/srep16600

Abstract

Climate variability is changing on multiple temporal scales, and little is known of the consequences of increases in short-term variability, particularly in endotherms. Using mortality data with high temporal resolution of zebra finches living in large outdoor aviaries (5 years, 359.220 bird-days), we show that mortality rate increases almost two-fold per 1°C increase in diurnal temperature range (DTR). Interestingly, the DTR effect differed between two groups with low versus high experimentally manipulated foraging costs, reflecting a typical laboratory ‘easy’ foraging environment and a ‘hard’ semi-natural environment respectively. DTR increased mortality on days with low minimum temperature in the easy foraging environment, but on days with high minimum temperature in the semi-natural environment. Thus, in a natural environment DTR effects will become increasingly important in a warming world, something not detectable in an ‘easy’ laboratory environment. These effects were particularly apparent at young ages. Critical time window analyses showed that the effect of DTR on mortality is delayed up to three months, while effects of minimum temperature occurred within a week. These results show that daily temperature variability can substantially impact the population viability of endothermic species.

Highlights

IntroductionFor example one can arbitrarily choose to average climatic variables over one or two weeks before each day
A large diurnal temperature range (DTR) substantially increased mortality rate and this effect was modulated by minimum temperature, age and environment, but not by developmental conditions
That DTR affects mortality is relevant because climate change is associated with changes in temperature variability on short time scales, i.e

Summary

Introduction

For example one can arbitrarily choose to average climatic variables over one or two weeks before each day Such arbitrary choices may not reflect the timeframe over which the biological effects occur, and this approach implicitly makes the unlikely assumption that all days within the selected time interval have equal effects on the phenomenon that is studied. Large broods are a poor developmental environment that causes pervasive negative effects during adulthood in many species[39,40,41,42,43], and this manipulation allows us to investigate whether effects of DTR depend on phenotypic quality. Since DTR represents a challenge, DTR will have more pronounced effects on mortality in animals that experience(d) poor quality environments

Methods

Results

Conclusion