Large diurnal temperature range increases bird sensitivity to climate change.

Area of Science:

• Ecology
• Climate Change Biology
• Animal Physiology

Background:

• Climate variability is increasing across temporal scales.
• The consequences of short-term climate variability on endotherms are not well understood.
• Diurnal temperature range (DTR) is a key aspect of climate variability.

Purpose of the Study:

• To investigate the impact of diurnal temperature range (DTR) on endotherm mortality.
• To compare the effects of DTR in different foraging environments (lab vs. semi-natural).
• To determine the temporal dynamics of DTR and minimum temperature effects on mortality.

Main Methods:

• Utilized high-resolution mortality data from zebra finches in outdoor aviaries over 5 years.
• Analyzed 359,220 bird-days of data.
• Employed critical time window analyses to assess delayed effects.

Main Results:

• Mortality rate nearly doubled with each 1°C increase in DTR.
• DTR effects on mortality varied with foraging costs and minimum temperatures.
• DTR impacts were more pronounced in semi-natural environments and on younger birds.
• Delayed mortality effects of DTR (up to 3 months) were observed, contrasting with rapid minimum temperature effects (within a week).

Conclusions:

• Daily temperature variability poses a substantial threat to the population viability of endotherms.
• Laboratory studies may underestimate the ecological impact of DTR due to simplified foraging conditions.
• Understanding DTR effects is crucial for predicting species' responses to a warming world.