Evolution takes time. Or does it?

Evolution can happen rapidly—it all depends upon how strong selection is and how much genetic variation there is in the trait being selected.  We tend to look at fossil bones, for example those along the horse lineage, and it seems like only a few millimeters of length are added per hundreds of thousands of years.  But in fact, these traits can vary quite a bit—even within populations—and if you have lots of individuals and lots of points in time, sometimes you can see really noticeable changes in short times.  The classic examples are Darwin’s Finches, that can significantly evolve larger or smaller bills during times of great stress.

That’s the Academy’s bird expert Jack Dumbacher. I asked him about a paper published this week in Current Biology about birds evolving shorter wings over a time-span of a mere thirty years. The evolutionary advantage? To avoid becoming roadkill.

In the US alone, an estimated 80 million birds are killed each year by cars. But the paper’s two authors, Nebraska researchers Charles and Mary Brown, noticed that fewer of the swallows they’ve studied for the past 30 years were becoming roadkill. This finding was surprising, since there are more cars on the road now than in the 1980s, and more of the swallows make their homes near the highways.

The researchers recently collected hundreds of dead cliff swallows from roadways, railroad tracks and other nesting areas, and noticed that “there were fewer road kills, and the birds found dead along highways had longer wing spans,” Charles Brown says. “I wanted to know if there was selection for particular characteristics in those dead birds.”

So he and his colleagues began a retrospective analysis, measuring the specimens in his 30-year collection. According to ScienceNOW:

The birds that were being killed, further analysis revealed, weren’t representative of the rest of the population. On average, they had longer wings. In 2012, for example, the average cliff swallow in the population had a 106-millimeter wingspan, whereas the average swallow killed on the road had a 112-millimeter wingspan.

The results suggested cliff swallows were undergoing morphological changes through natural selection.

Jack explains this adaptation. “Shorter wings—just like shorter cars – usually means a shorter turning radius. So if the birds need to make a rapid change in course, smaller wings might help facilitate this.”

The cliff swallows aren’t the first bird species to evolve quickly in response to human impacts. “One of my favorite examples is bird song in human habitats,” Jack says. “Our roads and neighborhoods are full of noises—air conditioners, traffic and other machines. Some of these produce noise in certain frequencies that can drown out or obscure bird song.  Researchers here and abroad have shown that many birds have noticeably shifted their song frequencies to avoid our ‘white noise’ and be better heard in human environments.”

Jack appreciates the work of the Browns in determining these shorter wingspans. “We often drive our commute and watch this or that, and sometimes we even ask ourselves whether, ‘Hmm, sure does seem like there are fewer roadkill than last year.’  Even a simple question like this can be incredibly difficult to even verify, but then to do all of the work to find the cause of the change—that can be very difficult to do.  They clearly have that restless scientific mind that doesn’t rest until they find a solid answer…”

I guess it takes one to know one.

Image: Ingrid Taylar/Wikipedia

If we tried to turn our heads like owls, we’d die. It’s that simple. Sudden gyrations of the head and neck in humans have been known to stretch and tear blood vessel linings, producing clots that can break off and cause a deadly embolism or stroke.

So medical researchers and illustrators at Johns Hopkins decided to find out how owls can rotate their heads up to 270 degrees in either direction. Using several previously frozen dead owls, the team injected contrast dye into the birds’ blood vessels, which were then meticulously dissected, drawn, and scanned to allow detailed analysis.

The team discovered four major biological adaptations that help prevent injury from rotational head movements in the owls. Variations to the animals’ bone structure and vascular network support its top-heavy head.

The owl illustrations won first-place in the posters and graphics category of the National Science Foundation’s 2012 International Science & Engineering Visualization Challenge.

We have to go to the salon for a fancy hairdo, but for some breeds of pigeons, it’s all in the genes! “There are some 350 [pigeon] breeds with different sizes, shapes, colors, color patterns, beaks, bone structure, vocalizations and arrangements of feathers on the feet and head—including head crests that come in shapes known as hoods, manes, shells and peaks,” says Michael D. Shapiro of the University of Utah.

Shapiro led a team of researchers who sequenced the genomes of several different breeds of pigeons and found a single mutation in a gene named EphB2 that causes head and neck feathers to grow upward instead of downward, creating head crests. And the diversity in crests is amazing, says Shapiro. “Some are small and pointed. Others look like a shell behind the head; some people think they look like mullets. They can be as extreme as an Elizabethan collar.” This research appears in the current issue of Science.

Homing pigeons certainly use compass-like techniques to find their way, but that doesn’t entirely explain their homing skills. U.S. Geological Survey scientist Jonathan Hagstrum was curious, why, for instance, tens of thousands of pigeons were lost in a 1997 race that crossed paths with the Concorde.

Hagstrum believes that homing pigeons also use infrasound—a low-level sound that many animals, but not humans, can detect. The birds make a kind of mental map from the sounds. According to Science Now:

Infrasound is generated when deep ocean waves send pressure waves reverberating into the land and atmosphere. Infrasound can come from other natural causes, such as earthquakes, or humanmade events, such as the acceleration of the Concorde. The long, slow waves move across vast distances.

You can find this research (without an infrasound map, alas) at The Journal of Experimental Biology.

Spinning, cresting, and finding home… We hope you enjoyed this bird’s-eye view of recent research headlines.

Image: DickDaniels/Wikipedia

We love parasitic insect stories and this one is a doozy—a beautiful, yet evil creature, the emerald cockroach or jewel wasp, that paralyzes and then zombifies cockroaches. The female wasp behaves this way to lay one solitary egg on the cockroach. When the egg hatches, the larva emerges and eventually eats its way into the belly of the roach. There, the larva will make a cocoon and grow into a beautiful new wasp. This part is all old news—and for more gory details, see Carl Zimmer’s post on National Geographic, complete with video!

But here’s the new part: before the larva makes its cocoon, it completely sterilizes the inside of the not-surprisingly filthy cockroach!

Cockroaches carry bacteria and other disease-carrying microbes around in their bellies—very unhealthy for growing wasp larvae. German researchers found that the larvae secrete “several types of antibiotics, specifically the chemicals mellein and micromolide,” according to LiveScience, that kill even the nastiest of microbes.

The research, published last week in the Proceedings of the National Academy of Sciences, finds these secretions promising for developing future human antibiotics.

If you’re a fish, how do you climb a waterfall? Well, if you’re a Nopili goby, the same way you eat, with your mouth, according to new research in PLoS ONE. The fish is known to inch its way up waterfalls as tall as 100 meters by using a combination of two suckers; one of these is an oral sucker also used for feeding on algae.

The researchers filmed jaw muscle movement in these fish while climbing and eating, and found that the overall movements were similar during both activities. (A video of the climbing can be found at Discover.) The researchers note that it is difficult to determine whether feeding movements were adapted for climbing, or vice versa, but the similarities are consistent with the idea that these fish have learned to use the same muscles to meet two very different needs of their unique lifestyle.

ScienceShot describes this as “exaptation—when a structure that was meant for one function is co-opted for another.”

Finally, ever since I saw the headline, “Birds May Get Emotional Over Birdsong,” it made me think of this line from High Fidelity (the movie, but likely the Nick Hornby book, too), “Did I listen to pop music because I was miserable? Or was I miserable because I listened to pop music?”

Well, it turns out that birds don’t get that emotional over their kin’s tweets, but researchers at Emory University found that white-throated sparrows experience some of the same emotions as a human listening to music. The recent study, published in the Frontiers of Evolutionary Neuroscience, demonstrates that taste is everything for these songs.

“We found that the same neural reward system is activated in female birds in the breeding state that are listening to male birdsong, and in people listening to music that they like,” says Sarah Earp, lead author of the study. Turns out another male hearing that same male birdsong likens it to music from scary scenes of a horror movie.

For more about this bird-brained study and its origins, check out this press release.

(Title thanks to the 1980s TV show)

Image: Sharadpunita/Wikipedia

When fighting disease, a bird under the weather tends to act very similar to a human battling the flu. In a recent study of house finches, Maxine Zylberberg, a postdoctoral fellow at the Academy’s Department of Ornithology & Mammalogy, observed both sick and well birds to assess their behaviors.

Researchers found that an ailing bird would hunker down on one side of its cage. It would tuck its head down, puff up its feathers, eat little or nothing, and become very inactive. And the focal individual of the study—the healthy bird—often tried to stay as far away as possible. Sound familiar?

Although other studies show that some animal species can recognize and avoid their sick fellows, Zylberberg’s research, published in the February 2013 issue of Biology Letters, is the first to describe such behavior in an avian species. It also established a link in the finches’ behavior to the relative strength or weakness of the healthy bird’s immune system.

A New York native who moved to San Francisco as a middle school student, Zylberberg visited the Academy often and eventually studied with Jack Dumbacher as a college student. She now focuses on describing and understanding the diversity of viral communities in birds and conducted the month-long study as a Ph.D. student at UC Davis in 2010.

Placing the locally caught, wild finches in groups of three, Zylberberg positioned a healthy focal individual with a sick bird on one side and another healthy bird on the other.

“The sick bird did not actually have an infectious disease,” she explains. Rather, it was merely injected with inactivated pieces of bacterial cell wall. “Its body recognized it as a pathogen and mounted an immune response. Anyone looking at the bird would say it looked sick.”

During the eight- to twelve-hour illness, Zylberberg compared behavioral differences among the sick and healthy birds and recorded the part of the cage the central, healthy individual spent its time.

“That’s when it got interesting,” she laughs. Birds who strongly invested in behavioral tricks to avoid their sick brethren had weaker immune function. Conversely, birds who socialized during the peak of another’s illness had very strong immune function.

“This is a key takeaway,” Zylberberg explains. “Scientists tend to look at behavioral defenses versus immune defenses through a separate lens. Until now, a link between the two has not been documented.”

Zylberberg believes this knowledge will help scientists fight viruses such as Avian flu or West Nile virus, or other zoonotic pathogens that jump from wild animal to human populations.

“Currently, we use mathematical models and computer simulations to predict the spread and timing of disease,” she explains. “Understanding the behavioral component of illness enables us to refine our assumptions and make better predictions.”

Barbara Tannenbaum is a science writer working with the Academy’s Digital Engagement Studio. Her work has appeared in the New York Times, San Francisco Magazine and many other publications.

Scientists who study birds have known this for a while.

The Academy’s Curator and Department Chair of Ornithology & Mammalogy, Jack Dumbacher, explains, “Beaks can tell us many things—often they reveal the foods that birds might eat and how they might forage, but they might also be useful for mating displays, building special nests, or improving the sounds of their vocalizations.”

Does the size of the bill also matter? Russell Greenberg, of the Smithsonian Migratory Bird Center, and his colleagues thought so. They study song sparrows living in the US—near the coast and inland—and noticed something interesting about these familiar feathered friends. For the subspecies closer to the coast, the beak bills were smaller. Those more inland, larger. But why?

“No one could figure out what this is an adaptation for,” Jack says.

Greenberg had a hunch it had to do with heat. See, birds don’t sweat. Or perspire.

“And with a thick downy plumage,” Jack says, “they may have to work to keep cool on a hot summer day.  Birds often pant, ruffle their feathers, and even move air through their feathers to keep cool. They can also radiate heat off their bills.”

Greenberg et al decided to investigate this last point by studying two song sparrow populations on the East Coast and two on the West Coast—inland vs. coastal subspecies.

For the first study, published last week in PLoS ONE, the researchers used thermal imaging to measure body and bill temperature of Eastern song sparrow populations.  The researchers found that the hotter the temperature, the warmer the bill—by about 5-10°C.

The researchers concluded that the birds dissipated heat through their beaks and birds in warmer climates would need larger beaks to do the job. In their studies, the scientists discovered that inland birds with larger bills dissipated over 30% more heat than coastal birds with smaller bills.

For the next study, published in the journal Evolution last week, the researchers took a look California song sparrow specimens housed in various museum collections, including the collection here at the Academy.

Collections like the Academy’s are useful, Jack says, because “each of our specimens has information about when and where they were collected.  Combining this with careful bill measurements allowed the researchers to correlate bill size with locality, and locality with annual temperatures.  It takes thousands of birds to do this kind of comparison, so collections like those of the Academy were critical to the study.”

In fact, the scientists studied almost 1500 specimens from nine different museums.

Not surprisingly, says the article, “song sparrows [specimens] showed increasing body-size-corrected bill surface area from the coast to the interior…” In other words, the hotter the habitat, the larger the beak size for dissipating heat.

“It is exciting to see such compelling explanations for the differences found in the field,” Jack says of his colleagues’ work.  “Interestingly, many of the coastal or sea-side sparrow races also have darker colors—perhaps also better for absorbing the sun’s heat in these cooler environments.”

Image: badjoby/Flickr

A team of scientists, led by Ryan M. Carney at Brown University, have now taken that first Archaeopteryx fossil and analyzed the famous dinosaur-bird’s color and flight abilities.

A few years ago, some of the same scientists found a way to determine the color of feathered dinosaurs by looking at melansomes in fossils. As Carl Zimmer describes in his Discover blog:

Depending on the size, shape, and spacing of melanosomes, they can produce a range of hues. It turns out that melanosomes are incredibly rugged, sometimes enduring for millions of years.

(Science in Action covered this research here.)

Placing the fossil in a powerful type of scanning electron microscope, Carney and his colleagues measured the length and width of the Archaeopteryx’s sausage-shaped melanosomes, roughly 1 micron long and 250 nanometers wide. To determine the melanosomes’ color, the team compared the Archaeopteryx melanosomes with those found in 87 species of living birds, representing four classes: black, gray, brown, and a type found in penguins. “What we found was that the feather was predicted to be black with 95 percent certainty,” Carney says.

Next, the team sought to define the melanosomes’ structure with greater accuracy. For that, they examined the fossilized barbules—tiny, rib-like appendages that overlap and interlock like zippers to give a feather rigidity and strength. The barbules and the alignment of melanosomes within them, Carney said, are identical to those found in modern birds.

“If Archaeopteryx was flapping or gliding, the presence of melanosomes would have given the feathers additional structural support,” explains Carney. “This would have been advantageous during this early evolutionary stage of dinosaur flight… We can’t say it’s proof that Archaeopteryx was a flier. But what we can say is that in modern bird feathers, these melanosomes provide additional strength and resistance to abrasion from flight, which is why wing feathers and their tips are the most likely areas to be pigmented.”

The research was published today in Nature Communication.

Illustration: NobuTamura

To attract mates, male bowerbirds play many roles—artist, decorator, architect, and a bit of an M.C. Escher. Australian researchers have found that not only will these birds build a castle and courtyard for their ladies, but they also employ forced perspective when doing so—a little trickery up their sleeves, um, wings.

Twenty species of bowerbirds live in Australia and Papua New Guinea. The males build a bower to attract females and decorate the area around the bower with brightly colored objects, shells, leaves, sticks, flowers, and so forth.

One species, the great bowerbirds, builds a bower avenue that leads to a courtyard that displays these objects. In 2010, Deakin University scientists found that when arranging the objects, the male birds create an optical illusion called forced perspective. The larger objects are moved to the back of the courtyard, farther away from the bower; smaller objects are placed closer to the entrance of the bower. The researchers believe that from inside the bower, a female bowerbird, viewing the objects, will think them all the same size.

“This gives the illusion that the court is smaller than it is and anything displayed within the court is larger than it really is,” Deakin’s John Endler explains. “We know that this doesn’t happen by chance. When we improved or reversed the size order of the objects in the courts, the males put them back within three days. Bower geometry is obviously very important to them.”

A new study by the same Deakin team explains why this geometry is so important. The better the forced perspective works, the more lovin’ the male bowerbird will get, says Endler. “The best predictor of mating success… is when we consider how the gradient looks from the female’s point of view: males that construct courts that look evenly patterned to the female within the bower attract the most mates.” You can check out one such lucky male in this video.

The recent study was published in last week’s Science; the 2010 paper appeared in Current Biology.

Want to learn more about crazy animal mating habits? Come visit the Academy’s upcoming Animal Attraction exhibit, opening February 11.

Image: JJ Harrison

Researchers in New Zealand trained pigeons to acquire abstract numerical rules using the same techniques used on monkeys over a decade ago. Science News explains that after training, the birds had to “put pairs of numbers up to nine in order.” The pigeons could match monkeys number for number in competency, the scientists found.

The researchers posit two evolutionary possibilities: either numerical competence was a convergent evolution in primates and birds OR it’s a homologous trait derived from a common ancestor. Either way, what other birds, mammals and insects might also be able to perform these numerical feats with a little training? The researchers are confident there are likely more.

Why do birds make illogical decisions? Why do people? Researchers at Oxford University (the same folks that brought us the crow tool-use study) tested eight European starlings in decision-making. The birds were given choices of pecking two colored-keys, each rewarding the bird with a different type of food or prey. When presented the choices simultaneously, the birds became confused and made a poor decision, choosing the less tasty and nutritious option. When presented separately, in a sequence, however, the birds chose wisely.

The researchers call this irrational decision making a “less-is-more effect” and believe the same is true in human decision-making. Science offers a great human psychological perspective on this study.

And birds aren’t the only creatures we can learn from! Another recent study on sea snails shows that learning through irregularly timed lessons, rather than rigorously scheduled ones, is more effective for the snails and potentially human students. Read more here.

Image: P. Huey/Science