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Mercury hurts birds and people: what we can learn from studying our feathered friends
By: Jenny R. Isaacs
January 07, 2013
An interview with Claire Varian-Ramos, a part of our on-going Interviews with Young Scientists series.
Black-capped chickadee. Recent research has shown that many U.S. songbirds are being impacted by mercury pollution. Photo by: Alan D. Wilson, www.naturespicsonline.com.
Like humans, birds are creative and their intelligence is among the highest in the non-human world. In fact, according to young avian researcher and life-long naturalist/bird watcher Claire W. Varian-Ramos, being called a "bird brain" should be taken as a compliment. For almost two decades she has conducted field work and formal study into the lives of birds and appreciates their adaptability and individuality. She teaches and writes often about birds; her published research draws on both lab and field studies of birds such as belted kingfishers, tree swallows, bald eagles, Eastern bluebirds, zebra finches, red-backed fairy-wrens, bald eagles, Nelson and saltmarsh sparrows.
"Even common species like rock pigeons or house sparrows can be fun to watch and you never know when you are going to see an interesting behavior... Birds are incredibly intelligent in comparison to most other taxa and I think it is being increasingly recognized that the phrase 'bird brain' may be a complement rather than an insult," Varian-Ramos told mongabay.com in a recent interview.
"Human induced rapid environmental change...is the leading cause of species endangerment. Introduction of chemical pollutants is one of the major ways that humans have altered the natural environment (in addition to habitat destruction, invasive species introduction, over harvesting and climate change) and threatened wildlife (and human) populations," she says.
Recently Varian-Ramos has been studying the connections between humans and our feathered friends through the lens of pollution effects, specifically mercury’s affect on bird biology and behavior. After previous studies demonstrated the ability of environmental contaminants such as mercury to result in the birth of more females than males (sex ratio) in wild bird populations, similar findings have been reported for human subjects.
"Mercury is a potent neurotoxin affecting birds and other wildlife worldwide," Varian-Ramos wrote as co-author of a study published last year in Ecological Indicators. "Mercury contamination poses a threat to wildlife in ecosystems worldwide, particularly large, predatory species such as bald eagles (Haliaeetus leucocephalus). Mercury can affect behavior and reproduction in birds, and high levels in the diet can cause mortality."
Now a postdoctoral researcher and instructor at The College of William and Mary in Virginia, Claire’s work continues to focus on human-caused rapid environmental change and its harmful effects on birds. In a recent 2012 article on the effects of mercury on birds at a contaminated river site, published in the Journal of Avian Biology, Claire explained as co-author, "Mercury is a ubiquitous environmental pollutant that can negatively impact physiology and behavior of vertebrates, causing sub-lethal changes in condition and reducing fitness." In this study, her team studied three species at contaminated sites and all three exhibited sex ratios shifted towards females "in the predicted direction of greater production of females, and at a magnitude of 5-15% from that observed at reference sites."
Varian-Ramos has discovered that, like people, birds do not react uniformly to environmental contamination. After replicating circumstances sadly common in the wild—as a member of the Institute for Integrative Bird Behavior Studies—Varian-Ramos' interdisciplinary research team will soon publish the details of their lab study which investigated the variety of negative behavioral, physiological, and developmental effects of continued low-level mercury poisoning of songbirds.
"Our study is the first to examine the impact of mercury on offspring sex ratios in birds, and therefore contributes to our understanding of the potential for this persistent biomagnifying contaminant [mercury] to alter fitness and effective population size in wildlife," she says.
Interestingly, her study found that after being exposed to mercury, some bird families suffered negative impacts on breeding and feeding rates while other families' breeding rates were unaffected or their feeding rates increased.
Varian-Ramos' ecotoxicology research on bird poisoning and responses to contamination have important implications for conservation and the health of the environment for both birds and people.
"Ecotoxicology aims to explain how these pollutants are affecting ecosystems, and ultimately, what steps can be taken to mediate or ameliorate these effects…[it] helps us to understand and mitigate our effects on the world. One major limitation is that some pollutants, once present in the environment, are persistent and nearly impossible to either remove or break down. In these cases, ecotoxicology can inform us on the damage done, but there may be little we can do to fix the problem," Varian-Ramos told mongabay.com.
In a January 2013 interview, Claire Varian-Ramos discussed the impact of mercury pollution on birds, why birds are smarter than we think, and her favorite places to go birding.
AN INTERVIEW WITH CLAIRE VARIAN RAMOS
Claire Varian-Ramos in the lab.
Mongabay: What is so awesome about birds?
Claire Varian-Ramos: What I find most fascinating about birds is their behaviors. One example is the behaviors that have evolved in some species to attract mates. From the complete transformations that birds of paradise perform in courtship displays, to cooperative dances in manakins, to the dawn chorus that can be heard in any backyard, sexual selection has produced the most beautiful, unique, and extreme displays seen anywhere in the animal world. Birds also complete some of the most amazing physical feats of any animals. Migration takes arctic terns from the pole to pole every year, albatrosses travel over 1,500 miles per trip to supply their chicks with food, and blackpoll warblers fly non-stop over water from Cape Cod to South America, losing as much as a quarter of their body mass along the way.
Most species of birds are also diurnal and very active, which makes them easy and fun to watch. Because of this it is much easier to be a bird watcher than a mammal or herp watcher. They are also found pretty much everywhere. Even in the middle of the city, there are birds. I’ve watched birds while stuck in traffic, waiting for people to show up for meetings, and even while working on this interview (a red-breasted nuthatch decided to cache some seeds in the siding of my house a little while ago). Even common species like rock pigeons or house sparrows can be fun to watch and you never know when you are going to see an interesting behavior.
One final thing I am grateful for as an ornithologist who frequently gets to handle wild birds; birds don’t have teeth.
Mongabay: What is the smartest thing a bird has done which you’ve seen, heard, or read about? Are they smarter than we think?
Other groups of birds may also be smarter than we give them credit for. On the field site where I did my dissertation research, we had one female red-backed fairy-wren who lived to be at least 11 years old, which is very old for 6 gram bird. We affectionately called her "Granny." Because she lived on the field site, every year we would try to trap her and her mate to get measurements and also try to find her nests so we could monitor them. As she got older, she changed her behavior in response to our presence. She started flying up into the trees whenever she saw a person, which made it nearly impossible to trap her. She also started walking through dense grass to get to and from her nest, rather than flying directly to it like other females. She was the only bird on our site who adopted these behaviors.
Mongabay: Where did you get your start/your love of birds and nature? Did you ever consider doing anything else?
Claire Varian-Ramos: I have been fascinated by animals for my entire life. I was very lucky that my parents recognized this and encouraged my interests. It also helped that they loved the outdoors too. We took a lot of family camping trips and I had pretty much every field guide I could get my hands on and was always trying to identify every bird, flower, and chipmunk I saw. I don’t think I knew I wanted to be a biologist when I was young, but I remember a conversation I had with my mom in my sophomore year high school. I was about a month into my first formal biology class and was absolutely enthralled by the whole subject. I came home one afternoon and asked my mom what kind of careers I could have in biology.
"Well, you could be a doctor," she said.
"No, I don’t really like people that much."
"You could be a vet."
"Hmmm… I think seeing hurt animals everyday would make me sad."
"You could be a field biologist."
"People do that?"
The summer after my junior year I volunteered on my first field project trapping small mammals. After senior year I volunteered on a bird mist-netting project, and then it was a done deal. I knew I wanted to study birds. During college I majored in biology and environmental studies and worked field jobs in the summers for more experience. When I got to grad school I discovered that I also love teaching biology and so my career goal now is to be a college professor so that I can teach in addition to continuing my research.
MERCURY POLLUTION, BIRDS, and PEOPLE
Bald eagle. Photo by: Rhett A. Butler.
Mongabay: How is mercury impacting birds and the food-web generally?
Claire Varian-Ramos: Mercury is a naturally occurring element present in the earth’s crust; however human activities have greatly increased the amount of available mercury in the environment. The largest anthropogenic source of mercury is coal fired power plants as elemental mercury present in the coal is released into the atmosphere when the coal is burned. Mercury in the atmosphere is deposited into aquatic systems through rain and snow. Manufacturing and artisanal mining are also significant point sources of mercury, usually directly contaminating waters. Once elemental mercury gets into the aquatic system, microbes in the water can convert it to elemental mercury to methylmercury, which is much more bioavailable and toxic. Methylmercury bioaccumulates in organisms and biomagnifies up the food chain, so species higher on the food chain, like birds, are at greater risk than those lower on the food chain. Because mercury usually occurs in aquatic ecosystems, until recently, only fish eating birds, like loons, bald eagles, and osprey, were thought to be at risk for mercury poisoning. However recent studies have revealed that insect eating birds, like vireos, chickadees, and wrens, that live adjacent to polluted environments have mercury levels similar to fish eating birds; the mercury is not remaining isolated in the aquatic ecosystem, but is escaping out into adjacent terrestrial ecosystems. It is not completely clear how this occurs. It may be that insects whose larvae are aquatic introduce mercury into the terrestrial food web after they emerge from the water and are eaten by terrestrial predators, like spiders. In both aquatic and terrestrial birds, field studies have revealed that elevated mercury levels result in reduced reproductive success, hormonal disruptions, immune suppression, and numerous behavioral changes including reduced complexity of learned songs and reduced parental activity. Our lab based studies have confirmed all of these effects in addition to effects that are difficult to study in the field such as on memory, flight performance, gene expression, and physiological stress.
Mongabay: What levels of mercury are safe for birds? How will your study help in assessing a "safe level" and how is that determination made?
Claire Varian-Ramos: I wouldn’t say there is a level of mercury that is "safe" for birds. One problem with a lot of toxicological studies is that they focus on the LD50 (lethal dose, 50%), or the dose of a contaminant at which 50% of exposed individuals die. This is a pretty narrow measure of the effects of a contaminant. An individual can survive but fail to reproduce and, at the population level, that is equivalent to that individual dying as it does not contribute to the next generation in either case. What we have focused on in our studies is the effects of chronic low level exposure which is more likely to be what birds experience in the field. We are looking for more subtle, sub-lethal effects that are likely to have an impact on individual fitness in a natural situation. Different effects occur at different levels of mercury. For example, behavioral effects, such as problems with learning and memory, occur at much lower levels than many of the physiological effects. Also, there is a lot of variation in the sensitivity of different species. Not all birds react to mercury in the same way and so using a single value for all species is an over simplification. That being said, it is not possible to test every end point in every species. The best we can do is to provide as much information to regulators as possible, which they can use to make a conservative estimate of the effects of mercury on wild birds.
Mongabay: How does your work in behavioral, physiological, and developmental effects of poisoning (on birds) overlap with, build upon, and complement ecotoxicology?
Mongabay: What changes can humans make to reduce the effects of mercury on birds? And do you see your work playing a role in affecting change for birds/the environment?
Claire Varian-Ramos: The biggest single source of mercury pollution is coal fired power plants. Reducing the amount of mercury in emission from these plants would go a long way to slow the increase in mercury pollution. The EPA is in the process of enforcing new regulations on mercury emissions from power plants in the US, but there is projected to be a huge increase of coal combustion in developing countries, so the US's contribution to global mercury pollution may be a drop in the bucket. The EPA has also increased regulation of mercury pollution from other industrial sources in recent years. The problem is that in areas with historical pollution there is little that can be done to remove mercury from an ecosystem. Since mercury is an element, it doesn't break down over time and is only removed from ecosystems very slowly (in the South River in western Virginia there hasn’t been an appreciable decrease in mercury in the fish in 30 years). What we can do is gain a better understanding of what species are likely to be effected (e.g. not just aquatic species) and what kinds of sub-lethal effects occur that might be over looked. This can help us understand what damage has already been done and what populations may need additional support to help offset the effects of the pollution.
Mongabay: What are the environmental implications from the mercury effects on birds you’ve discovered? I.e. How could this be affecting other species? Soil, air, or water quality?
Mongabay: Might your work on mercury levels in birds have any implications for human health?
Claire Varian-Ramos: For the last couple years I have been studying the effects of mercury on learned bird song. Birds use song for attracting mates and defending territories. Most Passerine birds (aka songbirds) learn their song from their fathers. The process of song learning is analogous to speech learning in humans in that it occurs mostly within a critical window in development and uses similar brain regions and even similar genes. I have found that zebra finches exposed to mercury from a young age produce songs that are significantly lower pitched and less complex. In most species, females prefer males with more complexity in their song. Mercury also causes developmental delays in language in humans. I am now working to try to identify the mechanisms through which mercury effects song in birds and this could help us understand the developmental effects in humans as well.
Mongabay: When scientists examine and report on human-caused mercury poisoning of the environment, is there an inevitable intersection of ethics and politics with conservation biology?
Claire Varian-Ramos: I think there is often a conflict between economic development and conservation biology. It often comes down to whether more value is placed on human economic wellbeing or environmental wellbeing. Mercury pollution is a perfect example of this. It is estimated that the EPA’s new regulations for mercury emissions from power plants will cost $10 billion dollars to implement and may increase a family’s monthly energy bills by $3-$4. Some might argue that is too high a cost to pay to protect wildlife, but considering the longevity of mercury in the environment, I think it is an issue we need to start considering now before mercury levels are high enough to cause an environmental crisis. Additionally, mercury contamination has important implications for humans as well, since neonatal exposure to mercury though a mother’s diet during pregnancy has been shown to have substantial effects on children.
Mongabay: You have conducted indoor and outdoor studies of birds. Can you discuss the different advantages/disadvantages of lab studies (versus in-the-wild studies) including how the study setting affect conclusions?
Claire Varian-Ramos: Lab based studies allow you to control for confounding variables that can limit the interpretations of field studies. In most field ecotoxicological studies, a contaminated site is compared to a nearby uncontaminated (reference) site that is as similar as possible. However, there may be other differences between the sites besides contaminant levels that affect the species you study, so there is a correlation between contaminant levels and effects, but that may not reflect actual causation of those effects. Conducting a lab based experiment can confirm the effects seen in the field and allow you to be more confident of your interpretation of field data. You can also more finely grained data because you can reliable sample the birds whenever is needed without needing to find and catch them. One of the drawbacks of lab based experiments is that they are not always realistic reflections of the field. A bird in an aviary has unlimited food and no predators, so in many ways it faces fewer challenges than it would in the wild. This may mean that lab based studies underestimate severity of the effects of contaminants.
LEARNING AND THE FUTURE
House wren, another common U.S. species that is imperiled by mercury pollution. Photo by: Rhett A. Butler.
Mongabay: Would you like to comment on the ethical/moral aspects of reproducing conditions of mercury poisoning on lab subjects/birds?
Claire Varian-Ramos: The ethical aspects of dosing studies is something that I am concerned about. Ultimately, I feel that the benefit of the information we are gain to whole communities of wild birds outweighs the harm caused to a small number of captive bred birds. If we hope to help conserve populations in polluted areas, we need to understand both the effects the pollution is having and the mechanisms through which these effects occur. These mechanistic studies are nearly impossible in a field setting. Additionally, lab based experiments establish causation not just correlation, which is important for conservation managers who are trying to establish damage caused by pollution and seek restoration or remediation funds from polluters. Finally, we do everything in our power to make sure our animals are as comfortable as we can make them. Because we are interested in the more subtle, sub-lethal effects, you can't tell just by looking the difference between a bird in our experiment who has been exposed and one who has not. They all appear to look and act similarly, and it is only through long term observation and careful measurement that the effects become apparent. All of our procedures and care protocols are approved and overseen by the Institutional Animal Care and Use Committee (IACUC) at William and Mary which consists of scientists and veterinarians concerned with the health and welfare of laboratory animals.
Mongabay: You’ve traveled a lot for bird study: favorite places to see birds?
Claire Varian-Ramos: One of the things I love about international travel is getting to see completely different communities of birds. In North America, I can usually classify an unknown bird into a general group and then figure out what it is from there (e.g. "Oh, that’s a sparrow, let’s flip to the sparrow section of the bird book"). When I first got to Australia for my dissertation research I was completely lost. I had no idea even where to start when identifying birds. It was really fun to start all over again learning new bird groups.
I think the best birding I’ve ever experienced was along the Gulf Coast of Louisiana during spring migration. While there in March and April of 2002, I saw an amazing diversity of marsh birds, including just about every heron and egret, huge flocks of dunlin and sanderlings, and a wide selection of migratory song birds in beautiful spring plumage. Highlights included a king rail with her chicks, flocks of black skimmers foraging, and a vagrant varied bunting in stunning blue and purple plumage.
Another place I love to bird is in Central Park. Because there is little green space around New York City, birds get concentrated into the park. It’s especially fun during migration when the trees can seem to be dripping with birds.
Mongabay: I’ve heard many ecologists say that birds are hard to study: what makes them so hard to study?
Claire Varian-Ramos: I'm not sure birds as a whole are any more difficult to study than other taxa. Most are species are diurnal, noisy, and active, which makes them easy to find relative to something like a wolverine or rattlesnake. I think difficulty varies by species. Each species has its challenges. It just takes patience to learn the behaviors of your particular species that will allow you to gather the information that you need. I was fortunate in my choice of study species for my dissertation. Red-backed fairy wrens live low in the understory and nest about knee height in grass and shrubs. Because of this they are relatively easy to catch (you can “herd” them into a mist net) and the nests are easily accessible. I learned all of their calls and became very good at tracking them through the dense undergrowth to their nests. There are definitely other species that pose other challenges. Canopy species are difficult to observe and catch. Corvids learn to avoid traps. Goshawks will attack researchers near their nests and can be quite dangerous.
Mongabay: What do you learn from teaching? What makes a good teacher?
Claire Varian-Ramos: I think teaching is the one of the most rewarding parts of my job. I love working with students from different backgrounds. Each student brings a different perspective and different interests to the research and makes the whole project stronger. I think good teachers excite and inspire their students. Also teachers need to be compassionate and encouraging, because sometimes science is frustrating and it is important for students to learn to troubleshoot and work through their problems. Finally, I think it is important to let students to be creative and to come up with their own solutions.
Mongabay: What would you like to be your greatest contribution to the field of ornithology/zoology?
Claire Varian-Ramos: I hope to continue to combine teaching and research as I go forward with my career. It’s hard to know exactly where my career will go from here, but I hope to continue working with students to understand how the changes that humans have made to the global ecosystem affect avian populations and to use that information to help preserve species and the communities in which they live.
Mongabay: You've had a lot of success in your career to date, what advice would you give students interested in wildlife conservation and research?
Claire Varian-Ramos: My biggest piece of advice is to follow your passion. If you study what you love, you will find your career rewarding and have the inspiration to work through the long hours and frustration that are inherent in science. I would also advise students to try to get research experience as early as possible. If you are in high school, try to find researchers working in your area and ask if you can volunteer on their project. Most wildlife biologists would be eager to have an enthusiastic young volunteer to help them even for only a few hours a week. In college, try to get involved in research early. Find a professor whose research you are interested in and contact them about doing research in their lab. It is particularly important to take the initiative at larger schools because often times most of the research opportunities go to graduate students and undergraduates need to be very proactive to get that experience. Research experience will help you to get hired after college and make you more attractive to potential graduate advisors. Finally, don’t be afraid of math. Getting experience with statistics, modeling, GIS, and other mathematically based skills will not only help you succeed in your career but will make you a better scientist.
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