Field of Science


Your Bird Feeder Could Be Bad for Birds

A free meal might seem like just the thing for your bird friends in winter, especially if that meal takes place in front of your picture window. But your feeder could be harming some bird species more than it's helping them. Even if it's a squirrel-proof seed tube or a pinecone rolled in peanut butter, there's still no such thing as a free lunch.

"We are really only in the early stages of understanding exactly what effects bird feeding is having on our wild bird populations," says Kate Plummer, an ecologist at the British Trust for Ornithology. Britons love to feed the birds. The BTO says that about half of everyone in the United Kingdom does it.

To find out how extra food during the winter months might affect wild birds, Plummer and her colleagues used populations of blue tits (Cyanistes caeruleus) that had never set eyes on a bird feeder. The birds lived at nine different sites in the woods. Researchers set up feeders to provide six bird groups with food (either straight fat, or fat plus vitamin E) while the other three got nothing. Over the course of three years, they rotated which bird populations were fed so they could better compare the results.

The scientists weren't interested in how extra food affected the birds eating it—they wanted to know what happened in the next generation. In nest boxes the following spring, they found that birds that had eaten at feeders hatched smaller chicks. Ultimately, fewer of these chicks grew up and left the nest.

Plummer says there are a few possible explanations. The fatty diet, for one, may have made birds nutritionally unbalanced by the time it came to egg-laying season. An earlier study that fed blue tits peanuts instead of straight fat found that it was beneficial to the next generation (though there were other differences between the studies too).

Feeders might also allow weaker birds to survive the winter, eventually hatching scrawnier chicks and bringing the whole population's average down. Or extra food in winter might encourage birds to invest resources in egg-laying, only to find come spring that their nests aren't in a great spot for food after all. The real answer may be a combination of factors, Plummer says.

Two other recent studies of woodland tits found that supplementing their food over the winter led to fewer chicks raised in the spring. But a similar study in woodpeckers found just the opposite. Bird feeders might be helpful for some species and harmful for others, possibly due to their different nutritional needs.

There may also be "winners and losers of bird feeding," Plummer says, that depend on the combination of species sharing a feeder. Dominant species might outcompete other birds, for example. Birds at feeders might also share diseases while they're pecking at the same seeds.

"People shouldn't stop bird feeding," Plummer says, at least not yet. It's too early to assume that feeding birds is always harmful. So go ahead and fatten up your feathered friends this winter. That is, as long as you can live with the possibility that the scene through your picture window isn't doing them any favors.

Image: David Lewis (via Flickr)

K. E. Plummer, S. Bearhop, D. I. Leech, D. E. Chamberlain, & J. D. Blount (2013). Winter food provisioning reduces future breeding performance in a wild bird Scientific Reports DOI: 10.1038/srep02002

Runners: Stop the Pronation Panic

If you walk into a sporting goods store and ask for shoes, you're likely to be thrown on a treadmill and have your strides dissected on video as if you were crossing an Olympic finish line. Salespeople will give you a thorough analysis of your gait. They may break the news that you "over-pronate," rolling your foot inward to some degree at the end of each step. Don't worry! It's common—and they sell a shoe made for your specific flaw. It's all very scientific, except that it isn't.

Rasmus Nielsen, a sport science graduate student at Aarhus University in Denmark, has seen the process from both sides of the in-store treadmill. When he first started running, he was told he should buy motion-control shoes to correct his pronation. Five years later, he started working in a running store.

"I was told to advise individuals to buy stability or motion control shoes if they were pronators," Nielsen says. "I started to ask the question, 'Why do we do this?' No evidence-based answer was provided."

Since becoming a physical therapist and seeing thousands of runners in his clinic—and dealing with his own running injury—Nielsen has developed a new perspective about where injuries come from. He doesn't think pronation or supportive shoes matter much at all. To add some evidence to the discussion, he conducted a study of more than 900 novice runners.

The subjects were healthy Danes of various ages and sizes—on average, 37 years old with a BMI of 26—who didn't run before the study. Physical therapists assessed their gaits and scored each person's feet as neutral, moderately or highly pronated, or moderately or highly supinated (rolling outward). Then subjects spent the next year running as much as they wanted. They logged their miles with a GPS watch and called the study leaders for an appointment if any injury cropped up.

Whatever their gait, all subjects were given identical "neutral" running shoes. Nielsen reasoned that if matching running shoes to foot type prevents injuries, then people with pronating or supinating feet should injure themselves sooner in these shoes than people with neutral feet.

That didn't happen.

Injuries were common; more than a quarter of the new runners were sidelined by injury at some point. But people's foot types had no relation to how soon they got injured. In fact, pronators had slightly (but significantly) fewer injuries per thousand kilometers run than neutral runners did.

Nielsen isn't the first researcher to find plot holes in the story told by shoe companies. A 2009 review concluded that there was no evidence behind the way different shoe types are prescribed. In 2011, a study of female runners found that those randomly assigned to wear motion-control shoes experienced more injuries than those assigned to other types of shoes.

Since the current study only involved uninjured, novice runners, the authors point out that motion-control shoes could be helpful to people who've already had an injury. It's also possible that the most extreme pronators are more prone to injury; in the study, this group was so small—only 18 people—that no real conclusions could be drawn about them. Yet for garden-variety pronators, there was clearly no extra injury risk.

These days, Nielsen says he can run in any type of shoe, once he gets used to it. He thinks how people train matters much more for their injury risk. Worrying about your sneakers, he says, isn't worth it. "I would definitely advise other runners [to do] otherwise than I did."

Image: by Danielle Walquist Lynch (via Flickr)

Nielsen, R., Buist, I., Parner, E., Nohr, E., Sorensen, H., Lind, M., & Rasmussen, S. (2013). Foot pronation is not associated with increased injury risk in novice runners wearing a neutral shoe: a 1-year prospective cohort study British Journal of Sports Medicine DOI: 10.1136/bjsports-2013-092202

How to Detune Someone with Perfect Pitch

Granted, it's a prank you can play on only 1 in 10,000 people. But if you find one of those rare individuals who can name any note they hear, with just a brief manipulation you can set that power awry. You can later console your subject with a reminder that, after all, nobody's perfect.

A children's choir that I used to sing in always performed the carol "Once in Royal David's City" at a certain concert, and the boy soprano who sang the opening solo would be sent up to a high chapel balcony along with a man who had perfect pitch. The adult would hum the correct note in the boy's ear, apparently, so that he could begin the solo out of a dramatic silence. (Looking back, I'm not sure sending someone up to blow very softly on a pitch pipe wouldn't have accomplished the same thing—but the addition of the superpowered helper made the whole thing more thrilling.)

People with perfect, or absolute, pitch can identify any notes they hear, and can tell you if those notes are a little sharp or flat. Stephen Hedger, a graduate student at the University of Chicago who's studying both cognitive psychology and musicology, has perfect pitch. After discovering that his perception could be skewed distressingly by someone fiddling with a tuning knob while he played the keyboard, he decided to test just how absolute "absolute pitch" really is.

Hedger gathered 13 subjects who'd scored as high as possible on a test of absolute pitch. At the beginning of the experiment, they listened to a series of notes; for each one, subjects had to identify the name of the note and whether it was in tune. The notes included everything from middle C to the B above it, and each note had three versions: one in tune, one slightly flat, and one slightly sharp.

(The out-of-tune notes were off by 33 "cents." The distance between any two notes, say C to C#, is 100 cents. Most people can detect a difference of just 25 cents, so a 33-cent difference—a third of the way to the next note—would be comfortably noticeable to all but the tone-deaf.)

Next, subjects listened to the entirety of Brahms's Symphony No.1 in C minor. During the first movement, which is 15 minutes long, the recording ever so slowly went flat. The pitch crept downward at 2 cents a minute, ending a full 33 cents flat from the original. The remaining half-hour of the symphony was played in the new, flattened key. When asked, none of the subjects noticed said they noticed a difference in pitch.

Then subjects completed the pitch quiz a second time. Now, pitches that were flat sounded in-tune, and pitches that were in tune sounded a little out of tune. (The subjects still correctly identified sharp pitches.)

In a second experiment, instead of Brahms subjects heard a series of modern musical compositions that only include 5 pitches. Just as before, the music slowly drifted flat and then stayed that way. In the pitch quiz afterward, subjects misjudged all the flat and in-tune notes they heard—not only the five notes they'd listened to.

A brief time listening to out-of-tune notes was able to skew a person's whole internal scale. Yet when subjects heard test pitches played by an instrument they hadn't listened to during the experiment—for example, a set of piano notes after the Brahms symphony, which didn't include a piano—their judgements were correct again. It is "as if each instrument voice retains its own tuning," Hedger and his coauthors write in Psychological Science.

People with absolute pitch, those superpowered few, are thought to learn their pitches in childhood. The pitches aren't absolutely stable, though: the detuning study shows they can be bent and changed by music a person has recently heard.

In a video, senior study author Howard Nusbaum says that the group is now looking for ways to improve people's sense of pitch, rather than detuning it, by taking advantage of this flexibility. "We are constantly changing to meet the circumstances around us," he says. That means someday the rest of us may be a little more perfect.

Image: by Timothy Valentine (via Flickr)

Hedger, S., Heald, S., & Nusbaum, H. (2013). Absolute Pitch May Not Be So Absolute Psychological Science DOI: 10.1177/0956797612473310

Compost Program Could Bring Dangerous Fungus into NYC Homes

If Mayor Bloomberg's wildest decay-related fantasies are realized, New Yorkers will soon be sparing their food scraps from the garbage. A new composting program would encourage (or possibly require) people in the city to collect their food waste in a separate container. Yet Bloomberg may want to consider whether a Manhattan apartment has the square footage to fit both its residents and their potentially harmful compost fungi.

The New York City recycling plan, as described in the New York Times this week, would start out on a voluntary basis. Participants would gather their food waste in "containers the size of picnic baskets in their homes," then dump the compost in curbside bins for regular collection. Instead of going into landfills, that waste might be turned into biogas for electricity. Eventually, the program could become mandatory.

Vidya De Gannes, a graduate student at the University of the West Indies, St. Augustine campus, in Trinidad and Tobago, has been composting too. She made three kinds of compost, each based on one type of dried plant material (agricultural wastes from the processing of rice, sugar cane, or coffee) mixed with cow or sheep manure. De Gannes and William Hickey, a soil microbiologist at the University of Wisconsin, Madison, who's the senior author of the new study, say these composts are most similar to a homeowner's compost mix of grass and yard waste.

To study the biodiversity of species living in compost, De Gannes collected fungal DNA from her compost containers and sequenced it. In total, she found 120 different species of fungus. Each kind of compost had a unique mix of species living inside it.

She also turned up 15 fungus species that can cause disease in humans. These were present in every kind of compost and ranged from Aspergillus fumigatus, a common fungus that can cause lung infections in people with compromised immune systems, to other species that can infect the skin or eyes.

Although the composts De Gannes studied weren't quite what New Yorkers would be collecting in their kitchens—unless they're keeping pet sheep too—some of the potentially dangerous fungi she found have also turned up in studies of all-plant compost.

Keeping a compost bucket in an enclosed space is "potentially risky," Hickey and De Gannes wrote in an email. Fungal spores floating on the air can cause infections, especially in people with weakened immune systems. "Compost kept in an enclosed area like a small apartment would probably not have adequate ventilation."

To get some fresh air, composters might have to leave their apartments and go around the corner for an extra-extra-large soda.

Image: Waldo Jaquith (not, as far as I know, a dangerous fungus)

De Gannes, V., Eudoxie, G., & Hickey, W. (2013). Insights into fungal communities in composts revealed by 454-pyrosequencing: implications for human health and safety Frontiers in Microbiology, 4 DOI: 10.3389/fmicb.2013.00164

Baseball Players Make Worse and Worse Decisions as the Season Goes On

If their goal were to frustrate fans, they couldn't plan it any better. Major-league baseball players reach a low point in their decision making in September, just in time for playoffs. Across all teams, batters swing at more and more pitches they shouldn't as the season goes on.

They may just need a nap.

"Consistently getting too little sleep—even if it's just [by] one hour a night—can lead to a state of chronic sleep deprivation that can compromise performance," says Vanderbilt University neurologist Scott Kutscher. "Specifically, things like judgment and reaction time."

Judgment and reaction time are just what a baseball player needs when a ball is hurtling toward his body at 90 miles an hour: he has to decide whether to swing, then react quickly enough to actually get it done. And sleep deprivation is familiar to pro ball players, who have a packed schedule and frequently travel back and forth across the country.

To see whether baseball players suffer the effects of sleep loss as the season drags on (or skips along for six non-tedious months, depending on your inclinations), Kutscher and his colleagues looked at data from 2011 back to 2006, after the MLB cracked down on steroid use. For each team, they tracked how often players swung at pitches outside the strike zone.

Over the course of the season, the researchers saw a steady increase in how many out-of-the-strike-zone pitches players swung at. These badly judged swings went up by about six-tenths of a percent each month.

Then Kutscher and his colleagues tested that model on the data from the 2012 season. When the numbers from all the MLB teams were pooled together, the model was a tight fit. Out of 30 teams, 24 were swinging at more balls in September than in April. Kutscher presented the findings at a recent conference on sleep.

Other factors aside from sleepiness may be at work. Pitchers might be throwing better curveballs as the months pass, for example. But Kutscher says pitchers threw pretty much the same ratio of balls and strikes throughout the season; if they were improving a lot, you'd expect to see them throwing more strikes. (Not to mention that batters, too, are practicing and honing their skills during the season.)

Since the researchers looked at whole teams rather than individuals, it's also possible that a change in the roster during the season—say, the addition of less experienced players who are called up from the minors—has an effect. Kutscher doesn't think this could account for all the deterioration he witnessed, though.

"I am hesitant to argue that fatigue is 100% of the story," Kutscher says. "But we have findings that are consistent with what we know about fatigue and chronic sleep loss."

Pro ball players, and other athletes, might see their performance improve if they could avoid sleep deprivation. So stop shouting at that guy on your screen who just struck out—he needs to go home and get some rest.

Image: Ed Gaillard (via Flickr)

Moths Wait until Bats Lock On, Then Jam Their Sonar

If you are a human reader, you've probably never seen your lunch put up an invisibility shield and perform an evasive maneuver just as you reached for it. But spare a thought for the bats. If your peanut-butter sandwich were anything like a tiger moth, you'd have a hard time finding a meal.

Several kinds of insects are able to detect the echolocation calls of a bat that's approaching like an enemy submarine. Moths may fly in another direction if they hear a bat nearby, or even drop into an escape spiral. Some species of tiger moth, while making their dramatic maneuvers, also make clicking sounds that jam a bat's sonar.

"Jamming is the most effective defense against bats ever documented," says Aaron Corcoran, a postdoc who studies echolocation at the University of Maryland. The moths generate "bursts of ultrasonic clicks" like machine-gun fire—as many as 4,500 clicks a second—and those clicks mix with the echoes from the moth's body that the bat is listening for. "This distorts the echo signature, effectively blurring the acoustic image in the bat's brain," Corcoran says.

In a study published in PLOS ONE, Corcoran and his coauthors examined the timing of that jamming signal: how does a tiger moth decide when to start clicking? If it throws around its sound effects too freely, the moth risks drawing attention to itself (usually a bad idea for a prey species).

The researchers secured Bertholdia trigona tiger moths in dark chambers and played recordings of echolocating bats, observing which bat signals triggered clicking from the moths. Then they went into the woods and hung the moths on tethers from a device not unlike a giant fishing pole. (After each moth was "hoisted into the air," the paper explains, "the pole was shaken periodically by the experimenter to add motion to the tethered moth and to keep the moth flying.") Also hanging from the pole was a tiny microphone, which let the researchers record the sounds of approaching bats--as well as bats snagging nearby, non-tethered moths.

In a bat's hunt, there are three main phases: the search, when the bat scans the area with sonar; the approach, once the bat has found a target and begins sending faster, more intense sound pulses at it; and the "terminal buzz" as it homes in to make the kill.

The researchers found that tiger moths, dangling from their fishing poles, liked to start their sonar-jamming clicks early in the approach phase. "This allows the moth the maximum amount of time to jam the bat," Corcoran says. It also lets the moth make sure the bat's sonar is aimed at itself, and not at a nearby, less fortunate insect. Corcoran says, "The interesting part to me is that the moths appear very well adapted for determining precisely when they have been targeted by a bat."

Once a moth takes action, the approaching bat is in trouble, Corcoran says. A tiger moth sending out a jamming signal is about 10 times more likely to escape its pursuer than it would be otherwise. In his study, moths that sent out jamming clicks and simultaneously made an escape dive "got away every time." It's enough to make a hungry bat wish it had packed a sandwich.

Corcoran, A., Wagner, R., & Conner, W. (2013). Optimal Predator Risk Assessment by the Sonar-Jamming Arctiine Moth Bertholdia trigona PLoS ONE, 8 (5) DOI: 10.1371/journal.pone.0063609

Image: by Aaron Corcoran. You can find more photos, videos, and other tidbits at his website.

Now Available: A Chastity Belt for Your Mouth

Is your main problem with dieting that you have a whorish mouth? Instead of saving itself for the truly worthy suitors—the poached lean proteins and steamed vegetables with dressing on the side—does it open up for every corn chip and chicken wing that passes by?

Good news, tramp-trap! For only $2,000 plus airfare to Los Angeles, you can have a patch of spiky plastic mesh stitched onto your tongue.

Doctor Paul Chugay promises the procedure is quick and easy. You’ll be back at work the next day. And instead of snacking at your desk, you’ll be sipping a new all-liquid diet, because your lingual chastity garment makes it too painful to consume solid foods.

Patients can expect to lose 20 to 30 pounds in a month on his 800-calorie-a-day “liquid beverage plan,” Chugay says in a video* on his site, or as much as 50 pounds in two months. After that, according to a Time article, the patch will have to be removed; otherwise it may be absorbed into the flesh permanently. That tongue just can’t control itself.


*Website NSFW, thanks to perky plastic-surgery “after” photos everywhere.

Better IQ Testing for Animals: There's an App for That

It's 2013, and laboratory pigeons are demanding an upgrade. Well, maybe they aren't demanding so much as continuing to do whatever tasks get them their pigeon pellets. Nevertheless, switching from analog to digital testing could mean more rigorous studies, better statistics, and a chance for previously ignored animals to try their paws at cognition research.

One of the classic cognitive tests that psychologists like to give animals involves two or more strings. At the far end of one string, there's a treat. The animal has to figure out that tugging on the near end of this string will gradually bring the reward close enough to eat.

How classic is the string test? In a recent Animal Cognition paper, Edward Wasserman of the University of Iowa and his coauthors list 74 different papers involving this experiment. Animals subjected to string-pulling tasks have includes apes, monkeys, birds, cats, rats, and Asian elephants. The experiments have been limited, though, to animals that can grasp and pull on a string or rope. Another constraint is the time it takes an experimenter to physically set up the strings and refill the food dishes over and over again.

Wasserman and his colleagues used a pigeon focus group to try out a new kind of string test with no string at all. The whole thing took place on a touchscreen, which you can see above. When pigeons pecked at the square on the near end of a "string," the "dish" on the other end moved a little closer. One dish was an empty black box; the other was a photo of pigeon feed. When a pigeon reeled the food dish all the way in, a tasty (non-virtual) pellet dropped out of a dispenser.

The four pigeons in the study quickly got the gist of things, learning to peck the end of the string attached to the food. They started off with simple tasks, in which the strings were short and didn't cross over each other. Then the strings got longer, appeared at various angles, and eventually crossed. These tasks were increasingly challenging to the pigeons. But even for the hardest tasks, the first string they pecked was usually the correct one.

Unlike in a real string test, there was no pulling—no physical weight of food to focus on dragging closer. Still, Wasserman thinks the touchscreen experiment is an accurate substitute for the real thing. In videos like this one, you can see the pigeons bobbing their heads along the strings as they work, seeming to understand the logic of the puzzle. The authors compare the experiment to a game of Angry Birds, which also simulates real physics (albeit with slingshotted cartoon animals).

Also unlike a real string test, the researchers were able to instantly change the length or placement of the strings. They put their pigeons through tens of thousands of trials without much trouble. All of this means better statistical analyses and more reliable results are possible. Using a touchscreen "allows us to conduct experiments with much greater rigor than would otherwise be the case," Wasserman says.

The new method could also let researchers try this kind of testing on any animal that can work a touchscreen, Wasserman says—"even those without dextrous appendages." For example, fish. He also suggests mammals such as dogs, horses, or cows, as well as birds that can't use their claws like hands. One aquarium has already demonstrated that its penguins can play an iPad game. From the aquarium's video, though, it's unclear whether the penguin is truly enjoying the app for cats, or if trying to nab an onscreen mouse is turning it into an Angry Bird.

Wasserman, E., Nagasaka, Y., Castro, L., & Brzykcy, S. (2013). Pigeons learn virtual patterned-string problems in a computerized touch screen environment Animal Cognition DOI: 10.1007/s10071-013-0608-0

Image: Wasserman et al.