Weathering the storm: Do arctic blizzards cause repeatable changes in stress physiology and body condition in breeding songbirds?

Jesse S Krause,Jonathan H Pérez,Helen E Chmura,Simone L Meddle,Kathleen E Hunt,Laura Gough,Natalie Boelman,John C Wingfield

doi:10.1016/j.ygcen.2018.07.004

Abstract

Severe weather events are increasing worldwide because of climate change. To cope with severe weather events, vertebrates rely on the stress response which is activated by the hypothalamic-pituitary adrenal (HPA) axis to adjust physiology and behavior. Previous studies have detailed changes in baseline concentrations of the stress hormone corticosterone during a single storm event, but little data exists on how stress physiology and body condition are adjusted as the storm progresses across multiple days. This represents a serious gap in our understanding of how birds respond physiologically over the duration of a storm. We documented arctic snowstorms that occurred over five consecutive years that were endured by Lapland longspurs (Calcarius lapponicus; 2012–2016) and in three consecutive years by white-crowned sparrows (Zonotrichia leucophrys gambelii; 2014–2016). Data were collected on storm-free days, during snowstorms ranging in length from 1 to 3 days, and the day immediately following a snowstorm. The specific aims were to understand how stress physiology, measured at baseline and in response to restraint handling, and body condition changed over multiple days of the storm, and if these responses were consistent across years. Snowstorms did not affect baseline corticosterone concentrations for either species except for female Lapland longspurs and male white-crowned sparrows in 2014. Lapland longspurs, regardless of sex, increased stress-induced (restraint handling) corticosterone in response to snowstorms in all years but 2013, which was characterized by unusually harsh conditions. Both sexes of White-crowned sparrows showed a significant increase in the stress-induced levels of corticosterone during snowstorms in one of the three years of the study. Stress-induced corticosterone concentrations were only different across each day of the storm in one year of the study for Lapland longspurs. Changes in fat and body mass were not uniform across years, but measurable increases in fat stores and body mass were detected in males of both species during the first day of a snowstorm with declines typically occurring by the second day. Our study showed that severe weather events often caused rapid increases in HPA axis activity and body condition, but these profiles are likely dependent upon ecological and environmental context within the breeding season.

Highlights

When migratory songbirds arrive on their breeding grounds they face many environmental challenges that vary from year to year such as predation, snow cover, severe weather, social instability, and food shortages (Newton 2006; Wingfield et al 2015)
The goals of this study were to understand 1) if physiology and body condition changed in response to severe snowstorms, 2) if these responses changed over the duration of the storm and immediately after its conclusion, 3) if the responses differed by sex and species, and 4) if these responses were repeatable at the population level across years
In agreement with our hypothesis, HPA axis activity was predominantly higher on days with snowstorms compared to those without for Lapland longspurs while this was less supported for white-crowned sparrows

Summary

Introduction

When migratory songbirds arrive on their breeding grounds they face many environmental challenges that vary from year to year such as predation, snow cover, severe weather, social instability, and food shortages (Newton 2006; Wingfield et al 2015) Each of these factors can cause physiological and psychological stress that disrupt homeostasis. Baseline levels of corticosterone act primarily through high affinity mineralocorticoid receptors (MR) while stress-induced concentrations act on low affinity glucocorticoid receptors (GR) (Joëls et al 2008; de Kloet 2014) This creates a two-tier system of receptor activation by which physiology and behavior can be modified based on the level of HPA axis activation (Sapolsky, Romero & Munck 2000; Angelier & Wingfield 2013; de Kloet 2014)

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