Helen E. Chmura

The stress response is attenuated during inclement weather in parental, but not in pre-parental, Lapland longspurs (Calcarius lapponicus) breeding in the Low Arctic

Birds breeding at high latitudes can be faced with extreme weather events throughout the breeding season. In response to environmental perturbations, vertebrates activate the hypothalamic-pituitary-adrenal (HPA) axis and synthesize corticosterone, which promotes changes in behavior and physiology to help the animal survive. The parental care hypothesis suggests that the HPA axis activity should be downregulated during the parental stage of breeding to prevent nest abandonment. However, it is unknown what happens to HPA axis activity in response to severe weather at the transition from the pre-parental to parental stages of breeding. We sampled baseline corticosterone levels and the time course of corticosterone elevation over 60min of restraint stress and assessed body condition and fat stores in Lapland longspurs (Calcarius lapponicus) breeding in the Low Arctic in the presence and absence of snowstorms. The results showed that during the pre-parental stage, HPA axis activity was up-regulated in response to snowstorms, with corticosterone levels continuing to increase through 60min of restraint. However, once birds were parental, HPA axis activity was unaffected by snowstorms and levels peaked at 10min. Fat levels and body condition did not change in response to snowstorms but fat levels declined in males during the pre-parental stage. These data suggest that the parental care hypothesis can be applied to severe storm events; parental birds restrained the activity of the HPA axis, likely to focus on the reproductive effort that is already underway, while pre-parental birds greatly upregulated HPA axis activity in response to snowstorms to maximize self-preservation.

A mechanistic approach to understanding range shifts in a changing world: What makes a pioneer?

Highlights • Many species are expanding or contracting their geographic distribution.• Range changes are caused by climate change, human disturbance and invasive species.• What are the characteristics of pioneers in new habitat?• Individuals at the leading edge appear to be highly variable.• In range expanding songbirds responses to stress are extremely variable.

The effect of extreme spring weather on body condition and stress physiology in Lapland longspurs and white-crowned sparrows breeding in the Arctic.

Highlights • The spring of 2013 was extreme with record low temperatures and snow cover.• Arrival of migrant birds in Arctic was significantly delayed in 2013 compared to 3 other years.• Body condition was negatively affected in white-crowned sparrows and Lapland longspurs.• Stress physiology was increased in Lapland longspurs but not white-crowned sparrows.• Extreme events have the capacity to affect phenology, body condition and stress physiology.

Nestling growth rates in relation to food abundance and weather in the Arctic

ABSTRACT Raising nestlings to fledging is energetically demanding for songbirds, requiring parents to balance several major tradeoffs. Nestling growth rates are highly susceptible to variation in environmental conditions and parental investment, and highly variable environments with short breeding seasons such as the Arctic magnify these tradeoffs. Arctic-nesting passerines provide a good model system in which to explore variation within and between species in growth rates with regard to environmental conditions and the timing of clutch initiation. Here we investigated interannual and interspecies variation in nestling mass gain for 2 species of Arctic-breeding passerine, Gambels White-crowned Sparrow (Zonotrichia leucophrys gambelii) and Lapland Longspur (Calcarius lapponicus), across 2 years. The nestling period of 2014 was both colder (with lower minimum and maximum temperatures) and wetter (with 73% more rainfall) than 2013. Arthropod biomass was also reduced in shrub tundra in 2014 compared to 2013. Both species showed reductions in rate of daily mass gain of nestlings in 2014 compared to 2013, but we observed no significant difference between species. Furthermore, we found that in 2014 early nesting birds had higher rates of nestling growth than those initiating clutches later in the season. These findings suggest that overall environmental conditions were more challenging for raising nestlings in 2014 compared to 2013 and that these differences were manifested in a reduced rate of nestling mass gain in both species. Furthermore, both species showed a negative correlation between precipitation and growth rates, whereas only Lapland Longspur showed a positive correlation between growth rates and temperature.

Annual Hematocrit Profiles in Two Subspecies of White-Crowned Sparrow: A Migrant and a Resident Comparison

Hematocrit is an easily measured parameter that can be used to assess changes in oxygen carrying capacity necessitated by fluctuations in metabolic demands. Most hematocrit studies draw conclusions from changes in hematocrit that occur over a small sampling interval without an understanding of the variation that exists across the annual cycle. White-crowned sparrows provide an excellent model system due to the existence of a resident subspecies (Zonotrichia leucophrys nuttalli) that serves as a natural control for a migrant subspecies (Zonotrichia leucophrys gambelii). Comparing these two subspecies allows for the investigation of adaptive physiological changes at each life-history stage (i.e., migration, breeding, molt, etc.) in response to changing metabolic demands. Of particular interest, this subspecies comparison, by both calendar month and life-history stage, allows for the separation of adaptive increases in hematocrit due to migration from the natural seasonal variation in hematocrit. Hematocrit levels for males and females ranged throughout the year between 42%–47% and 40%–47% in the resident and between 45%–58% and 45%–56% in the migrant. In both subspecies, hematocrit levels were elevated during the breeding season compared to the nonbreeding season, and levels were reduced in females during egg laying. When grouped by life-history stage, hematocrit levels were always higher in the migrant compared to the resident. During the months in which migration occurred, hematocrit levels were 10%–12% higher in the migrant compared to the resident subspecies. These data suggest differential regulation of hematocrit between the two subspecies that may be attributed to phenotypic plasticity or genetic differences.

Effects of a social cue on reproductive development and pre-alternate molt in seasonally breeding migrant and resident female songbirds (Zonotrichia leucophrys)

ABSTRACT 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. Highlighted Article: Migrant and resident birds exhibit differences in reproductive development consistent with adaptive specialization in the use of photoperiodic cues, but not social cues, to regulate reproductive development.

Eavesdropping on the Arctic: Automated bioacoustics reveal dynamics in songbird breeding phenology

Soundscape-level acoustic recordings revealed delay in arrival of songbird community to arctic breeding grounds. Bioacoustic networks could vastly expand the coverage of wildlife monitoring to complement satellite observations of climate and vegetation. This approach would enable global-scale understanding of how climate change influences phenomena such as migratory timing of avian species. The enormous data sets that autonomous recorders typically generate demand automated analyses that remain largely undeveloped. We devised automated signal processing and machine learning approaches to estimate dates on which songbird communities arrived at arctic breeding grounds. Acoustically estimated dates agreed well with those determined via traditional surveys and were strongly related to the landscape’s snow-free dates. We found that environmental conditions heavily influenced daily variation in songbird vocal activity, especially before egg laying. Our novel approaches demonstrate that variation in avian migratory arrival can be detected autonomously. Large-scale deployment of this innovation in wildlife monitoring would enable the coverage necessary to assess and forecast changes in bird migration in the face of climate change.

Tundra avian community composition during recovery from the Anaktuvuk River Fire

In 2007, a fire burned over 100000ha along the Anaktuvuk River in Alaska, causing widespread ecological disturbance. Despite efforts to understand ecosystem recovery, little is known about higher trophic levels. Here, we present qualitative findings from a preliminary bird survey of the burn scar region, conducted in 2014, at three sites representing varying severity of burn damage. We found that abundance and species richness both appear higher at a site that experienced a moderate degree of burn damage than unburned control and severely burned sites. These findings suggest that the impacts of fires on bird communities may be minimal within 7 years post fire. Furthermore, our findings highlight the need for more rigorous efforts to understand the dynamics of tundra bird community fire recovery in a rapidly changing world.

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

Highlights • Stress physiology was analyzed in response to multi-day snowstorms in 5 years.• Baseline corticosterone was unaffected by snowstorms in all but two instances.• Stress-induced corticosterone were typically elevated during snowstorms.• Stress physiology was significantly different across a multiday storm in only one year.• Body condition tended to increase on the first day of the storm.

Biologging Physiological and Ecological Responses to Climatic Variation: New Tools for the Climate Change Era

In this mini-review, we discuss how biologging technology can be used to detect, understand, and forecast species’ responses to climate change. We review studies of phenology, thermal biology, and microhabitat selection as examples to illustrate the utility of a biologging approach in terrestrial and aquatic species. These examples show that biologgers can be used to identify and predict behavioral and physiological responses to climatic variation and directional climate change, as well as to extreme weather events. While there is still considerable debate as to whether phenotypic plasticity is sufficient to facilitate species’ responses to climate change or whether responses to short-term climate variability are predictive of climate change response, understanding the scope and nature of plasticity is an important step towards answering these questions. One advantage of the biologging approach is that it can facilitate the measurement of traits at the level of the individual, permitting research that investigates the degree to which physiology and behavior are plastic. As such, combining biologging with metrics of fitness can provide insight into how plasticity might confer population and species resilience to climate change. Increased use of biologgers in experimental manipulations will also yield important insight into how phenotypic flexibility allows some animals to mitigate the negative consequences of climate change. Although biologging studies to date have mostly functioned in measuring phenotypic responses to short-term climate variability, we argue that integrating biologging technology into long-term monitoring programs will be instrumental in documenting and understanding ecological responses to climate change.