Hummingbirds Live in a More Colorful World, Study Confirms
Hummingbirds live a more colorful existence than humans do, a new study published in the Proceedings of the National Academy of Sciences Monday confirmed.
While humans only have three color cones, birds have four, meaning they can theoretically see colors on the ultraviolet spectrum, National Geographic explained. Until now, however, no scientist had really tried to discover what a bird's eye view of color would look like.
"Humans are color-blind compared to birds and many other animals," lead study author and Princeton University assistant professor Mary Caswell Stoddard said in a Princeton press release. "Not only does having a fourth color cone type extend the range of bird-visible colors into the UV, it potentially allows birds to perceive combination colors like ultraviolet+green and ultraviolet+red — but this has been hard to test."
To overcome these difficulties, Stoddard and a team of scientists from Princeton, the University of British Columbia (UBC), Harvard University, University of Maryland and the Rocky Mountain Biological Laboratory (RMBL) set up a series of outdoor experiments with broad-tailed hummingbirds in Colorado. They wanted to test the birds' abilities to see nonspectral colors, colors perceived from widely distinct parts of the color spectrum.
The only nonspectral color humans can see is purple, which is not part of the rainbow.
"Instead of being formed by a single light or mixture of similar lights, purple is formed by simultaneously stimulating our non-adjacent red-sensitive and blue-sensitive cones in our eyes," study coauthor and UBC Ph.D. student Harold Eyster explained on Twitter.
Since purple is my favorite color, & birds are my favorite animals, I wondered, "Can birds see purple?" Today, our paper led by Dr. Cassie Stoddard with @dylanhmorris @B_G_Hogan @DavidInouye1 Ed Soucy is in @PNASNews that shows that yes, birds can! https://t.co/lcFuu2yt1l 3/n— Harold Eyster (@HaroldEyster) June 15, 2020
But birds, because of their fourth cone, can in theory see up to five nonspectral colors: purple, ultraviolet+red, ultraviolet+green, ultraviolet+yellow and ultraviolet+purple.
To test whether the birds really did see these colors, researchers placed feeders containing sugar and plain water in an alpine meadow next to LED tubes designed to emit a variety of colors, including nonspectral ones, the press release explained. The researchers conducted 19 experiments over three years, recording data from more than 6,000 feeder visits. They found that the birds could learn to visit the sugar water feeder even when the two LED tubes marking the feeders were indistinguishable to human eyes.
The details of color vision are usually studied in the lab, but we wanted to know how birds act in the wild. Thus,… https://t.co/3JoxVNIY29— Harold Eyster (@Harold Eyster)1592252910.0
"Seeing them do this right in front of my eyes is one of the most exciting things I've ever witnessed," Stoddard told National Geographic.
The hummingbirds could see purple, ultraviolet+green, ultraviolet+red and ultraviolet+yellow, the researchers confirmed, according to the press release.
University of Chicago evolutionary biologist Trevor Price, who was not involved with the research, told National Geographic that the findings marked a "big step forward" for understanding how birds and other animals see.
"We're really only beginning to scratch the surface in our understanding of color vision in animals," he said.
The scientists think the birds use their enhanced color vision to locate a wide variety of plants for nectar. They found that the birds would be able to distinguish nonspectral colors in 30 percent of birds' plumage and 35 percent of plants from a database.
Birds can see nonspectral colors, and these colors make up a substantial part of the bird visual environment. We ho… https://t.co/160gQITMyo— Harold Eyster (@Harold Eyster)1592252913.0
"The colors that we see in the fields of wildflowers at our study site, the wildflower capital of Colorado, are stunning to us, but just imagine what those flowers look like to birds with that extra sensory dimension," co-author David Inouye of the University of Maryland and RMBL said in the press release.
The findings also have conservation implications.
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By Joni Sweet
If you get a call from a number you don't recognize, don't hit decline — it might be a contact tracer calling to let you know that someone you've been near has tested positive for the coronavirus.
Interviews With Contact Tracers<p>Contact tracing is a public health strategy that involves identifying everyone who may have been in contact with a person who has the coronavirus. Contact tracers collect information and provide guidance to help contain the transmission of disease.</p><p>It's been used during outbreaks of sexually transmitted infections (STIs), Ebola, measles, and now the coronavirus that causes COVID-19.</p><p>It starts when the local department of health gets a report of a confirmed case of the coronavirus in its community and gives that person a call. The contact tracer usually provides information on how to isolate and when to get treatment, then tries to figure out who else the person may have exposed.</p><p>"We ask who they've been in contact with in the 48 hours prior to symptom onset, or 2 days before the date of their positive test if they don't have symptoms," said <a href="https://case.edu/medicine/healthintegration/people/heidi-gullett" target="_blank">Dr. Heidi Gullett</a>, associate director of the Center for Community Health Integration at the Case Western Reserve University School of Medicine and medical director of the Cuyahoga County Board of Health in Ohio.</p>
“You’ve Been Exposed”<p>After the case interview, contact tracers will get to work calling the folks who may have been exposed to the coronavirus by the person who tested positive.</p><p>"We give them recommendations about quarantining or isolating, getting tested, and what to do if they become sick. If they're not already sick, we still want them to self-quarantine so that they don't spread the disease to anyone else if they were to become sick," said Labus.</p><p>Generally, the contact tracer won't ask for additional contacts unless they happen to call someone who is sick or has a confirmed case of the virus. They will help ensure the contact has the resources they need to isolate themselves, if necessary. The contact tracer may continue to stay in touch with that person over the next 14 days.</p><p>"We follow the percentage of people that were contacts, then converted into being actual cases of the virus. It's an important marker to help us understand what kind of transmission happens in our community and how to control the virus," said Gullett.</p>
Why You Should Participate (and What Happens If You Don’t)<p>A <a href="https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(20)30457-6/fulltext" target="_blank">Lancet study</a> from June 16, which looked at data from more than 40,000 people, found that COVID-19 transmission could be reduced by 64 percent through isolating those who have the coronavirus, quarantining their household, and contacting the people they may have exposed.</p><p>The combination strategy was significantly more effective than mass random testing or just isolating the sick person and members of their household.</p><p>However, contact tracing is only as effective as people's willingness to participate, and a small number of people who've contracted the coronavirus or were potentially exposed are reluctant to talk.</p><p>"Contact tracers have all been hung up on, cussed at, yelled at," said Gullet.</p><p>The hesitation to talk to contact tracers often stems from concerns over privacy — a serious issue in healthcare.</p>
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Climate Explained is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.
If you have a question you'd like an expert to answer, please send it to email@example.com
What was the climate and sea level like at times in Earth’s history when carbon dioxide in the atmosphere was at 400ppm?<p>The last time global carbon dioxide levels were consistently at or above 400 parts per million (ppm) was around <a href="https://www.nature.com/articles/nature14145" target="_blank">four million years ago</a> during a geological period known as the <a href="http://www.geologypage.com/2014/05/pliocene-epoch.html" target="_blank">Pliocene Era</a> (between 5.3 million and 2.6 million years ago). The world was about 3℃ warmer and sea levels were higher than today.</p><p>We know how much carbon dioxide the atmosphere contained in the past by studying ice cores from Greenland and Antarctica. As compacted snow gradually changes to ice, it traps air in bubbles that contain <a href="https://www.cambridge.org/core/journals/annals-of-glaciology/article/enclosure-of-air-during-metamorphosis-of-dry-firn-to-ice/09D9C60A8DA412D16645E6E6ABC1892F" target="_blank">samples of the atmosphere at the time</a>. We can sample ice cores to reconstruct past concentrations of carbon dioxide, but this record only takes us back about a million years.</p><p>Beyond a million years, we don't have any direct measurements of the composition of ancient atmospheres, but we can use several methods to estimate past levels of carbon dioxide. One method uses the relationship between plant pores, known as stomata, that regulate gas exchange in and out of the plant. The density of these stomata is <a href="https://journals.sagepub.com/doi/abs/10.1177/095968369200200109" target="_blank">related to atmospheric carbon dioxide</a>, and fossil plants are a good indicator of concentrations in the past.</p><p>Another technique is to examine sediment cores from the ocean floor. The sediments build up year after year as the bodies and shells of dead plankton and other organisms rain down on the seafloor. We can use isotopes (chemically identical atoms that differ only in atomic weight) of boron taken from the shells of the dead plankton to reconstruct changes in the acidity of seawater. From this we can work out the level of carbon dioxide in the ocean.</p><p>The data from four-million-year-old sediments suggest that <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2010PA002055" target="_blank">carbon dioxide was at 400ppm back then</a>.</p>
Sea Levels and Changes in Antarctica<p>During colder periods in Earth's history, ice caps and glaciers grow and sea levels drop. In the recent geological past, during the most recent ice age about 20,000 years ago, sea levels were at least <a href="https://science.sciencemag.org/content/292/5517/679.abstract" target="_blank">120 meters lower</a> than they are today.</p><p><span></span>Sea-level changes are calculated from changes in isotopes of oxygen in the shells of marine organisms. For the Pliocene Era, <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2004PA001071" target="_blank">research</a> shows the sea-level change between cooler and warmer periods was around 30-40 meters and sea level was higher than today. Also during the Pliocene, we know the West Antarctic Ice Sheet was <a href="https://www.nature.com/articles/nature07867" target="_blank">significantly smaller</a> and global average temperatures were about 3℃ warmer than today. Summer temperatures in high northern latitudes were up to 14℃ warmer.</p><p>This may seem like a lot but modern observations show strong <a href="https://journals.ametsoc.org/jcli/article/23/14/3888/32547" target="_blank">polar amplification</a> of warming: a 1℃ increase at the equator may raise temperatures at the poles by 6-7℃. It is one of the reasons why Arctic sea ice is disappearing.</p>
Impacts in New Zealand and Australia<p>In the Australian region, there was no Great Barrier Reef, but there may have been <a href="https://link.springer.com/content/pdf/10.1007/BF02537376.pdf" target="_blank">smaller reefs along the northeast coast of Australia</a>. For New Zealand, the partial melting of the West Antarctic Ice Sheet is probably the most critical point.</p><p>One of the key features of New Zealand's current climate is that Antarctica is cut off from global circulation during the winter because of the big <a href="https://www.tandfonline.com/doi/abs/10.3402/tellusa.v54i5.12161" target="_blank">temperature contrast</a> between Antarctica and the Southern Ocean. When it comes back into circulation in springtime, New Zealand gets strong storms. Stormier winters and significantly warmer summers were likely in the mid-Pliocene because of a weaker polar vortex and a warmer Antarctica.</p><p>It will take more than a few years or decades of carbon dioxide concentrations at 400ppm to trigger a significant shrinking of the West Antarctic Ice Sheet. But recent studies show that <a href="http://nora.nerc.ac.uk/id/eprint/521027/" target="_blank">West Antarctica is already melting</a>.</p><p>Sea-level rise from a partial melting of West Antarctica could easily exceed a meter or more by 2100. In fact, if the whole of the West Antarctic melted it could <a href="http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.695.7239&rep=rep1&type=pdf" target="_blank">raise sea levels by about 3.5 meters</a>. Even smaller increases raise the risk of <a href="https://www.pce.parliament.nz/publications/preparing-new-zealand-for-rising-seas-certainty-and-uncertainty" target="_blank">flooding in low-lying cities</a> including Auckland, Christchurch and Wellington.</p>
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