In this new blog post, Mary Woodruff presents her recent work ‘Heat alters diverse thermal tolerance mechanisms: An organismal framework for studying climate change effects in a wild bird‘. She explains the importance of understanding thermal tolerance for conservation decision-making in the face of climate change, discusses the challenges of collecting data from nestling birds, and shares the factors she believes contribute to excellent research.
About the paper
This paper is about how wild birds respond to and cope with heat, which we are expecting with the future of climate change. What ‘tools,’ or response mechanisms do young birds have to cope with a particularly hot day and what are the consequences of coping with this hot day?
In response to temperatures elevated 4.5°C above naturally occurring nest temperatures, nestlings moved to cooler areas of the nest, they panted more, and they weighed less than control nestlings. We think this weight difference after just four hours means that panting may come at the cost of water loss. In the blood, heat induced physiological coping mechanisms – higher levels of heat shock protein (HSP) gene expression, alongside other changes related to antioxidant defenses and inflammation. Critically, all nestlings survived the challenge, and those exposed to milder heat were more likely to later return to breed in our population as adults. Early-life exposure to heat may influence which nestlings survive the first year of life, with the potential to shape species survival.
We are learning about how wild animals are coping with our changing environment. With this information, we can look for indicators of species success or challenges in the face of intensifying heat waves. Maybe we can use physiological measurements like HSP90 gene expression to determine how well a species is going to handle the future of climate change heat waves. We want to conserve all species threatened by climate change, but our resources are limited. Understanding wild animal thermal tolerance mechanisms gets us one step closer to creating data-driven tools for conservation decision-making.
Specifically for birds, now that we know that mild heat promotes nestlings returning as adults, but higher temperatures do not, we can use this information to design nest boxes to be cooler environments for nestlings. If we are going to provide nest boxes for birds, we are responsible for making them safe environments.
About the research
We took a multi-pronged approach, observing behavioral and physiological responses to a four-hour heat challenge, like what we might see at the beginning of a heatwave. Our work focused on wild tree swallows (Tachycineta bicolor) during a critical time in development, when nestlings were 12 days old.
We collected behavior data from wild nestlings using a small camera in the top corner of the nest boxes. We collected about 1 terabyte of video data. We collected blood samples from the nestlings, which we used to collect data on gene expression. We measured nestling weight using a scale, and wing length using a stopped wind ruler.
In the next two years, we went back out to our field sites and identified breeding birds to see how many of them were returning nestlings now breeding as adults.
We did a ton of testing of the tools we used to conduct the heat challenge and the experiment in the field. This wasn’t a fail, but I think it’s interesting to think about a published study beginning with large handwarmers in paper bags along a lab bench so we could see how hot they get, or with me in my living room weaving grass into nests and then putting these dummy nests in nest boxes with warmers to test the temperatures of nests… all before my experimental methods ever interacted with a live bird.
The other challenge came with the fact that these birds love wetlands. Our field site was a managed wetland along a river that would flood the dirt road, so we rented a suburban to get through the deep puddles in the road and make it to our nest boxes. We turned that suburban into a mobile field lab! We would park at a distance from our study nest box, prep the trunk with our scales, blood sample tubes, and datasheets, then bring the nestlings there for the ~10 minutes that we were collecting samples, before returning them to their nest. This made an otherwise grueling experimental design much more feasible. Although… the field site roads were closed on the weekends so on those days we walked our supplies to each nest box.
I was surprised by how much variation there was in HSP90 gene expression among siblings in the nest! This variation opens so many questions related to individual nestling behavior, parental genetics, and natural selection that we could not address in this study, but I am very curious about.
There are many future applications of this research. I hope that the field begins to compare species responses to heat waves so that we can better assess which species are equipped to cope with climate change effects in the future, and which species may need concerted conservation efforts to preserve population survival.
About the author(s)
I have always loved nature – I majored in Animal Behavior, Ecology, and Conservation at Canisius University, at the time, because I wanted to rehab domestic animals. Well, I got introduced to research at Canisius and I was marveled by how, through research, I could make a career out of being curious. I would ask questions about the world and find answers that were not available before. I thought it was amazing to contribute a piece of knowledge to the world that someone could Google later and find an answer because of me. I still think that is one of the coolest things we do as scientists.
Hiking, birding, and woodworking are my main hobbies. I love having a creative outlet in woodworking, I recently finished making some pollinator houses! Now that my fieldwork is finished I get to bird just for fun.
I am currently an ORISE (Oak Ridge Institute for Science and Education) Quantitative Ecology & Epidemiology Postdoctoral Fellow with the USDA-APHIS Center for Epidemiology and Animal Health. In my postdoc I research international animal disease introduction risk into the US, so policy makers and wildlife managers can make better decisions about where to surveil and monitor for diseases, and we keep our animals healthy. Really, I help keep diseases out of our country so that we keep the bacon supply going. This work allows me to translate huge, national and international datasets into real-world problem-solving pieces of information. What I learned from my avian work is that I am driven by the applications of my research, and this postdoc gives me the opportunity to conduct science that directly informs USDA policy.
I am extremely grateful to regional Audubon Societies and scientific organizations that have been instrumental in funding my research. The Rosvall lab is a female led research group. Throughout my entire graduate career, I was surrounded by incredibly intelligent, driven, and productive women scientists and I found that environment very empowering. Kim Rosvall’s research group is continuing to work on avian responses to heat research, so check out her lab website for the latest updates.
A scientific team thrives when we hire and train individuals who are passionate about learning. While specific qualifications are important, focusing solely on them can limit the diverse perspectives and enthusiasm that drive discovery. Fostering research environments for growth and mentorship can create teams that are both highly skilled and deeply curious.
Like the blog post? Read the research here.
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