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Understanding how organisms respond to environmental perturbations is essential for coping with environmental challenges, especially when extreme global weather events are becoming more frequent due to climate change. We performed RNA sequencing on samples from wild, free-living male Lapland longspurs (Calcarius lapponicus) during their arrival on the breeding grounds and during incubation on the Arctic tundra of Alaska, USA. Samples were collected during an extremely cold arrival period in 2013 and incubation during a severe snowstorm in 2016. We performed RNA-seq analyses on liver, hypothalamus, heart, and gonad testicular tissues to understand how this Arctic species responds to an extreme weather event. influences the biological system. We present a high quality Lapland longspur genome assembly and gene annotation of Lapland longspurs, with whichand we identified differentially expressed genes associated with inclement weather events. We identified that FKBP5 was significantly up-regulated in the hypothalamus during a snowstorm, suggesting that FKBP5 is functionally important for theduring an environmental stress response. FKBP5 is reported to be a regulator of the Hypothalamic-Pituitary-Adrenal (HPA) axis during the stress-response, and acts to modulate glucocorticoid receptor sensitivity in mammals. FKBP5 acts as a co-chaperone, negatively regulating the glucocorticoid signalling pathway and provides a mechanism by which an individual can rapidly and accordingly adjust its HPA axis function in response to unpredictable environmental perturbations. Other pathways in the hypothalamus and other tissues were seen to be involved during these stressful conditions, included specifically those involved in metabolism, the immune response and the circadian cyclerhythms. Such findings will contribute to the understanding of gene expression changes in multiple physiological systems to mediate stress in wild free-living birds.

Extreme weather events are becoming more frequent because of climate change. Understanding how organisms respond to adverse environmental conditions is a prerequisite to coping with environmental challenges. We studied a unique set of samples collected from free-living Lapland longspurs (Calcarius laponnicus) during their arrival and incubation. Birds were sampled at an extreme arrival period, a typical arrival period, and incubation before and during a severe snowstorm. To understand how climate change influences the biological systems of wild birds, we performed RNA-seq on the liver, hypothalamus, heart, and gonad. Plasma levels of glucocorticoids were elevated in response to stress handling during the extreme spring and during the snowstorm. We identified storm-associated differentially expressed genes (DEGs). In particular, the gene encoding FKBP5 was up-significantly regulated in hypothalamus, suggesting that FKBP5 is functionally important for the response to inclement weather. FKBP5 is a regulator of the Hypothalamic-Pituitary-Adrenal (HPA) axis stress-response, and it acts to modulate glucocorticoid receptor sensitivity. FKBP5 acts as a co-chaperone, negatively regulating the glucocorticoid signalling pathway and provides a mechanism by which an individual can adjust to environmental perturbations. Such findings will build on our understanding of endocrine mediated stress and resilience in freely living animals in a changing world. Extreme weather events are becoming more frequent because of climate change. Understanding how organisms respond to adverse environmental conditions is a prerequisite to coping with environmental challenges. Wild animals are an excellent proxy, so we studied a unique set of samples collected from wild Lapland longspur (Calcarius laponnicus) breeding in Alaska, representing different tissues under exposure to different environmental conditions, including a severe snowstorm. To understand how climate change influences the biological systems of wild birds, we performed RNA-seq on different tissues including liver, hypothalamus, heart, and gonad, with the presence and absence of storm condition.We identified many storm-associated differentially expressed genes (DEGs). In particular, when comparing the differentially expressed genes in hypothalamus, the gene encoding FKBP5 is significantly up-regulated, which suggests FKBP5 is functionally important in response to storm conditions. FKBP5 is a regulator of the Hypothalamic-Pituitary-Adrenal axis and stress-response, and in response to stress FKBP5 modulates glucocorticoid receptor sensitivity. FKBP5 acts as a co-chaperone, negatively regulating the glucocorticoid signalling pathway and other biological functions. Such findings will provide the foundations to develop resilience strategies to mitigate potentially devastating effects in all life on earth including those of global agricultural importance.

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 while 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 1-3 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.

While the effect of weather on reproduction has been studied for many years in avian taxa, the rapid pace of climate change in arctic regions has added urgency to this question by changing the weather conditions species experience during breeding. Given this, it is important to understand how factors such as temperature, rain, snowfall, and wind affect reproduction both directly and indirectly (e.g. through their effects on food availability). In this study, we ask how weather factors and food availability influence daily survival rates of clutches in two arctic-breeding migratory songbirds: the Lapland longspur Calcarius lapponicus, a circumpolar breeder, and Gambel’s white-crowned sparrow Zonotrichia leucophrys gambelii, which breeds in shrubby habitats across tundra, boreal and continental climates. To do this, we monitored clutch survival in these two species from egg-lay through fledge at field sites located near Toolik Field Station (North Slope, Alaska) across 5 yr (2012–2016). Our results indicate that snowfall and cold temperatures decreased offspring survival rates in both species; although Lapland longspurs were more susceptible to snowfall. Food availability, quantified by pitfall sampling and sweep-net sampling methods, had minimal effects on offspring survival. Some climate models predict increased precipitation for the Arctic with global warming, and in the Toolik region, total snow accumulation may be increasing. Placed in this context, our results suggest that changes in snow storms with climate change could have substantial consequences for reproduction in migratory songbirds breeding in the North American Arctic.

Most seasonal species rely on the annual change in day length as the primary cue to appropriately time major spring events such as pre-nuptial molt and breeding. Thyroid hormones are thought to be involved in the regulation of both of these spring life history stages. Here we investigated the effects of chemical inhibition of thyroid hormone production using methimazole, subsequently coupled with either triiodothyronine (T3) or thyroxine (T4) replacement on the photostimulation of pre-nuptial molt and breeding in Gambel’s white-crowned sparrows (Zonotrichia leuchophrys gambelii). Suppression of thyroid hormones completely prevented pre-nuptial molt, while both T3 and T4 treatment restored normal patterns of molt in thyroid hormone-suppressed birds. Testicular recrudescence was blocked by methimazole, and restored by T4 but not T3,in contrast to previous findings demonstrating central action of T3 in the photostimulation of breeding. Methimazole and replacement treatments elevated plasma luteinizing hormone levels compared to controls. These data are partially consistent with existing theories on the role of thyroid hormones in the photostimulation of breeding, while highlighting the possibility of additional feedback pathways. Thus we suggest that regulation of the hypothalamic pituitary gonad axis that controls breeding may be more complex than previously considered.

To time reproduction optimally, birds have evolved diverse mechanisms by which they respond to environmental changes that help them anticipate and prepare for the breeding season. While residents initiate reproductive preparation and breed in the same geographic location, migrant birds simultaneously prepare for breeding and migration far from their breeding grounds. As a result, it is hypothesized that migrant and resident birds use environmental cues differently to prepare to breed and that there is adaptive specialization in mechanisms regulating reproductive preparation. Specifically, residents are expected to rely more on non-photic cues (e.g. food, temperature, social cues) than migrants. We tested this general prediction using a social cue manipulation. First, we compared the effects of subspecies-appropriate recorded male song on reproductive development in migrants and residents on a naturally increasing photoperiod. Second, we tested the sensitivity of migrant-specific life history events (fattening and pre-alternate molt) to song treatment. After 82 days, residents had higher luteinizing hormone and greater ovarian development than migrants, but song treatment had no effect on these metrics in either subspecies. Song advanced pre-alternate molt but had no effect on fattening in migrants. While our study does not support specialization in social cue use in migrants and residents, it is consistent with findings in the literature of specialization in photoperiodic response. It also demonstrates for the first time that social cues can influence molt in a migrant species. Additional findings from a pilot study looking at responses to a live male suggest it is important to test other kinds of social cues.

For wild free-living animals the availability of food resources can be greatly affected by environmental perturbations such as weather events. In response to environmental perturbations, animals activate the hypothalamic-pituitary-adrenal (HPA) axis to adjust physiology and behavior. The literature asserts that during weather events food intake declines leading to changes in HPA axis activity, as measured by both baseline and stress-induced glucocorticoid concentrations. Here we investigated how body condition, locomotor activity, and stress physiology were affected by varying lengths of a fast (1, 2, 6, and 24 h; similar to that experienced by free-living birds) compared to when food was provided ad libitumin captive wintering male white-crowned sparrows, Zonotrichia leucophrys gambelii, exposed to a short day photoperiod. Baseline corticosterone concentrations were increased for all fasting durations but were highest in 6 and 24 h fasted birds. Stress-induced corticosterone was elevated in 1 h fasted birds with a trend for the 2 h of fast; no other differences were found. Baseline corticosterone concentrations were negatively related to both total fat scores and body mass. All birds lost body mass regardless of fast length but birds fasted for 24 h lost the most. Fat scores declined in the 6 and 24 h groups, and no measureable changes were detected in pectoralis muscle profile. Locomotor activity was increased over the entire period in which food was removed regardless of fasting duration. Together this suggests that reduced food availability is responsible at least in part, for the rapid elevation both baseline corticosterone under any duration of fast and stress-induced concentrations during short-term fasts.