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The Fuzzy Fluffy Super-Cute Health Threat In Your Backyard

A day-old chick.
A day-old chick.
Image via Shutterstock.net.

An epidemic is moving across the United States. It has invaded 35 states and sickened 324 people, including 88 children. It has put 66 people into hospitals, and one of the sick people has died. And the Centers for Disease Control and Prevention, responding as it always does to outbreaks that menace Americans, is struggling with how to stop its advance—because the things causing the epidemic are widely distributed across the country, come from many places, and are hard to trace back to their source.

And also, are super-cute. The cause is backyard chickens.

Since January, and continuing into June, there have been seven separate outbreaks of Salmonella—each caused by a different strain of the bacterium and each stretching over multiple states, from 16 down to seven—that have been proved to originate in live chicks and ducklings bought by mail or in feed stores and kept at home or at a school.

Baby chicks and ducklings and the birds they grow into may not sound like much of a threat. But in addition to the 324 cases they have caused this year (so far; the CDC plans to update the case count in the next two weeks), backyard poultry caused 252 cases of illness last year, 363 cases in 2014, 514 cases in 2013 (including 356 cases caused by one Salmonella strain); and 334 in 2012. That is 1,757 cases in 5 years.

If that doesn’t seem like much, consider that 2013-14 saw the largest recent outbreak of Salmonella caused by raw poultry, traced back to chicken produced by the California company Foster Farms. That outbreak generated an enormous public health response, months of media coverage, and lawsuits. It caused 634 known cases. Over the same time period, backyard poultry sickened 877. Yet those illnesses seem to still be flying (sorry) under the radar.

“If you ask someone, ‘Can you get Salmonella from eating undercooked poultry?’ they are absolutely going to say Yes,” Megin Nichols, a public health veterinarian in the CDC’s foodborne outbreak response and prevention branch, told me. “But if you ask them, ‘Can you get Salmonella from touching your backyard chicken?’ they don’t necessarily know that.”

How Salmonella outbreaks linked to backyard chicken have risen since the 1990s, based on CDC data.
How Salmonella outbreaks linked to backyard chicken have risen since the 1990s, based on CDC data.
Original from Behravesh et al., Clinical Infectious Diseases, May 2014

Some of that disconnect may be cognitive dissonance. People buy backyard chickens to opt out of an industrial food system they perceive as unhealthy—so it takes some mental gymnastics to confront that the birds providing homegrown eggs (and sometimes meat) might be hazardous too. But, Nichols said, it might also be lack of awareness—that Salmonella, which resides in chickens’ guts even when birds look  healthy, and exits their bodies in their droppings, can spread all over them as they perch and take dust baths and preen.

“On their feet, on their feathers, on their beaks,” Nichols said. “And in the areas where they live and roam. So people are exposed when they clean the coop or otherwise maintain the poultry environment. But we also see people, especially young children, cuddling and snuggling them and kissing them.”

Finally, add in that most people don’t know Salmonella, along with other foodborne illnesses, doesn’t only cause a few days or weeks of lying flat and sticking close to the bathroom. An increasingly solid body of research links it to lifelong illnesses from arthritis to digestive problems to circulatory damage that leads to high blood pressure, kidney failure and stroke.

Casey Barton Behravesh, a veterinarian with a public health doctorate who directs the CDC’s “One Health” office, said this is a new problem. Exposure to live poultry used to be rare, and pretty predictable: It occurred when children were given fuzzy newborn chicks in Easter baskets. “Then in the early 2000s, we noticed a growing trend of more and more outbreaks occurring, not linked to little chicks and ducklings, and not among kids getting sick,” she told me. “It was adults getting sick, people who reported having backyard flocks, which was something we had never seen before.”

Educational material on backyard-poultry disease outbreaks.
Educational material on backyard-poultry disease outbreaks.
Image courtesy the CDC; original here.

People are being made ill because they don’t recognize they are at risk—but the structure of the industry, and the systems set up to monitor it, aren’t helping. The federal program that surveys diseases in live chickens, the USDA’s National Poultry Improvement Plan (NPIP) was set up to protect chicken health, not human health. So it tracks Salmonella strains that make chickens sick, but not the ones that cause human outbreaks, and until recently, it focused on the vast commercial poultry trade where those strains would cause costly damage.

Denise Brinson, a veterinarian who is the NPIP’s director, told me that because of the backyard-associated outbreaks, the agency has worked with the CDC to create a program addressing small suppliers. In 2014, it began allowing hatcheries that supply the backyard trade—which sell birds to feed stores and hardware stores, as well as direct to consumers—to join a testing program scaled to the size of their businesses and to advertise that they have NPIP certification.

But to look for that, would-be poultry buyers have to know where the birds are coming from, and that turns out to be more difficult than it should be. Federal investigators including Behravesh documented in 2012 and 2014 that the process of getting chickens to market isn’t a supply chain, it’s a tangle. Birds come from 20 different hatcheries in the US, but many of those hatcheries have contract farmers doing the daily work, and then combine those clutches to make up the millions of birds they ship each year. Because some hatcheries specialize in only certain breeds, they also may “drop-ship”—buy and ship birds from other hatcheries—to make up orders as well.

And at the sales end, birds from different farms and hatcheries may be commingled in the same store pen—increasing the possibility that Salmonella can spread among them, and making traceback to the birds’ origin an extraordinarily difficult task.

All of which means the onus is on individuals to protect themselves: owners of live poultry in backyard or schools, people who visit those owners, even people who handle baby chicks in the stores where they are sold. The CDC’s advice is to keep separate clothes and shoes to wear for feeding birds and cleaning their coops; make sure anyone who touches the birds or their area washes their hands right away; and remember that, no matter how adorable they are, backyard poultry are a food source, not a pet. Despite the temptation, they shouldn’t be smooched or snuggled—especially not by young children, whose immature immune systems put them at greater risk of infection.

“We do think that raising backyard poultry can be a fun and educational experience,” Nichols said. “But it is not the right experience for everyone.”

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Birds on Islands Are Losing the Ability to Fly

Before the arrival of humans—and the rats, cats, and other predators that we brought—New Zealand was an idyllic haven for birds. Without ground-dwelling mammalian hunters to bother them, many of the local species lost the ability to fly. There’s the kakapo, a giant, booming parrot with an owl-like countenance; the takahe, weka, and other flightless relatives of coots and moorhens; a couple of flightless ducks; and, of course, the iconic kiwi.

Kakapo (Strigops habroptilus) at night, Codfish Island, New Zealand. Photograph by Stephen Belcher, Minden Pictures, Corbis
Kakapo (Strigops habroptilus) at night, Codfish Island, New Zealand. Photograph by Stephen Belcher, Minden Pictures, Corbis

These birds are part of a pattern that plays out across the world’s islands. Wherever predators are kept away by expanses of water, birds become flightless—quickly and repeatedly. This process has happened on more than a thousand independent occasions, producing the awkward dodo of Mauritius, the club-winged ibis of Jamaica, and the tatty-winged flightless cormorant of the Galapagos.

The call of the ground is a strong one, and it exists even when the skies are still an option. Natalie Wright from the University of Montana demonstrated this by collecting data on 868 species. She showed that even when island birds can still fly, they’re edging towards flightlessness. Compared to mainland relatives, their flight muscles (the ones we eat when we tuck into chicken breasts) are smaller and their legs are longer.

“Pretty much all island birds are experiencing these pressures to reduce flight, even if some can’t go to the extreme,” Wright says.

Her results show that flying isn’t a binary thing, with a clear boundary between taking to the air and staying on the ground. Instead, there’s a full spectrum of abilities between aeronautical swifts and shuffling kiwis, and island birds exist on all parts of that continuum. “None of the species I looked at were flightless or close to being truly flightless,” says Wright. “There’s no point where, all of a sudden, they have much smaller flight muscles.”

Her study began about 20 years ago, when her undergraduate advisor David Steadman started weighing the flight muscles of birds at the Florida Museum of Natural History. When Wright got her hands on the data set, she noticed that fruit doves had smaller flight muscles on islands that were further from the mainland. She then travelled to five natural history museums herself to examine more skeletons. For each one, she measured the long bones in the lower legs and the size of the breastbone—the latter revealed how heavy the bird’s flight muscles would have been in life.

Across nine major groups of birds, with a wide range of lifestyles, body shapes, and diets, Wright found the same trend. On smaller islands with fewer species, no mammalian predators, and fewer birds of prey, birds have repeatedly reallocated energy from forelimbs to hindlimbs, away from big flight muscles and towards longer legs.

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To her surprise, the trend even applied to hummingbirds, for whom flying is an inextricable part of life. Hummingbirds hover in front of flowers to drink nectar. A flightless hummingbird is a dead hummingbird. And yet, even though “islands hummingbirds look like hummingbirds when they fly, they were still reducing their flight muscles and evolving longer legs on islands without predators,” says Wright.

The same was true for kingfishers, flycatchers, tanagers, honeyeaters, and other groups that are extremely dependent on flight. Wright studied the Todiramphus kingfishers across 27 Pacific islands. “Members on islands with fewer than 20 species of birds, which don’t have any predators that can kill an adult kingfisher, have much smaller flight muscles and much longer legs than any members on larger and more populated islands,” she says. “They sit on perches and fly out to grab prey. Their foraging style requires flight, but they’re edging towards flightlessness.”

Why? It’s easy to see why a diving bird like a cormorant or a ground-dwelling one like a kakapo might lose its ability to fly when predators are absent. But why should a hummingbird or kingfisher, which flies all the time, sacrifice some of its aerial prowess?

Because flight muscles come with a cost. Even at rest, larger ones require more energy to maintain. So if birds can get away with smaller ones, evolution pushes them in that direction. Large flight muscles are especially useful when birds take off. That’s the most energetically demanding part of flying, and the bit that’s most important for escaping from ground predators. If such predators are absent, birds can take off at a more leisurely pace, and they can afford to have smaller (and cheaper) flight muscles. (This might also explain why they developed longer legs: they take off more by jumping than by flapping.)

Wright’s results suggest that island birds might be more vulnerable to introduced predators than anyone appreciated. Even those that can fly aren’t as good at it as their mainland counterparts. They may also help to explain why island birds diversify into such wondrous forms. When they settle in a remote landmass, even the flying ones might quickly lose the power they need to cross oceans and find new homes.

Islands, it seems, create birds that stay on islands.

Paleo Profile: New Caledonia’s Giant Fowl

A restoration of Sylviornis. From Worthy et al., 2016.
A restoration of Sylviornis. From Worthy et al., 2016.

Life gets weird on islands. Some species, such as elephants, shrink over time, while forms of life that are tiny on the mainland expand to unheard of sizes. Among the best examples of this Island Rule—which is really more of an Island Puzzle—are birds. Over and over again, islands have hosted populations of ground-dwelling, supersized birds, such as one hefty fowl that strutted around New Caledonia.

François Poplin named the bird Sylviornis neocaledoniae in 1980. Exactly what sort of avian it was, however, has been in dispute ever since then. Poplin considered the helmet-headed bird to be related to cassowaries and emus, while other experts suggested that Sylviornis was much closer to turkey-like megapodes. Then further analysis of the skull led other avian experts to put Sylviornis in its own special lineage, the Sylviornithidae, asserting that the turkey-like features of the birds bones were a case of convergence.

In order to sort through this tangle, paleontologist Trevor Worthy and colleagues had a look at about 600 bones of the bird’s body. What they found supported some earlier suggestions about where the bird nested in the greater avian family tree – Sylviornis was a stem galliform, or a relatively archaic member of the group that contains turkeys, pheasants, and chickens. And this might rule out Sylviornis as the answer to a New Caledonian mystery.

Strange earthen mounds on New Caledonia were thought to be the nests of the massive Sylviornis. But this connection relied on the idea that the big bird was a megapode, as these birds characteristically deposit warm their eggs in holes or little hillocks of soil to gain warmth from rotting vegetation, the earth, or some other outside source. Now that Worthy and coauthors have pushed Sylviornis further away from the megapodes, the idea that the mystery mounds were made by Sylviornis now seems less likely. The anatomy of the bird’s feet, the researchers conclude, was at best suited to scratching at the dirt as if it were a supersized chicken. Perhaps, as paleontologists scratch at the soil themselves, they’ll uncover more clues about the life and times of this long-lost fowl.

Some of the Sylviornis long bones examined in the study. From Worthy et al., 2016.
Some of the Sylviornis long bones examined in the study. From Worthy et al., 2016.

Fossil Facts

Name: Sylviornis neocaledoniae

Age: Over 5,500 years ago until about 3,000 years ago.

Where in the world?: New Caledonia

What sort of critter?: A bird related to landfowl like turkeys and pheasant.

Size: Over two and a half feet tall and more than 60 pounds.

How much of the creature’s body is known?: Thousands of individual elements from the skeletons of multiple individuals.

Reference:

Worthy, T., Mitri, M., Handley, W., Lee, M., Anderson, A., Sand, C. 2016. Osteology supports a steam-galliform affinity for the giant extinct flightless birds Sylviornis neocaledoniae (Sylviornithidae, Galloanseres). PLOS ONE. doi: 10.1371/journal.pone.0150871

Previous Paleo Profiles:

The Unfortunate Dragon
The Cross Lizard
The South China Lizard
Zhenyuan Sun’s dragon
The Fascinating Scrap
The Sloth Claw
The Hefty Kangaroo
Mathison’s Fox
Scar Face
The Rain-Maker Lizard
“Lightning Claw”
The Ancient Agama
The Hell-Hound
The Cutting Shears of Kimbeto Wash
The False Moose
“Miss Piggy” the Prehistoric Turtle
Mexico’s “Bird Mimic”
The Greatest Auk
Catalonia’s Little Ape
Pakistan’s Butterfly-Faced Beast
The Head of the Devil
Spain’s Megatoothed Croc
The Smoke Hill Bird
The Vereda Hilarco Beast
The North’s Sailback
Amidala’s Strange Horn
The Northern Mantis Shrimp
Spain’s High-Spined Herbviore
Wucaiwan’s Ornamented Horned Face
Alcide d’Orbigny’s Dawn Beast
The Shield Fortress
The Dragon Thief
The Purgatoire River’s Whale Fish
Russia’s Curved Blade
The Dawn Mole
The Oldest Chameleon
The Wandering Spirit
Teyú Yaguá

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An Epidemic 14 Years Ago Shows How Zika Could Unfold in the US

An Aedes albopictus mosquito, which health authorities worry may begin to spread Zika.
An Aedes albopictus mosquito, which health authorities worry may begin to spread Zika.
Photograph by James Gathany, CDC.

If the Zika virus comes to the United States, we could face the threat of the same sort of virgin soil epidemic—an infection arriving in a population that has never been exposed to it before—that has caused more than 1 million known infections, and probably several million asymptomatic ones, in Central and South America. It’s nerve-wracking to wonder what that would be like: How many people would fall ill, how serious the effects would be in adults or in babies, and most important, how good a job we would do of protecting ourselves.

But, in fact, we can guess what it would be like. Because we have a good example, not that long ago, of a novel mosquito-borne threat that caused very serious illness arriving in the United States. And the data since its arrival shows that, despite catching on fairly quickly to what was happening, the U.S. didn’t do that good a job.

This possibility became more real Monday when the Pan American Health Organization released a statement that predicts Zika virus, the mosquito-borne disease that is exploding in South and Central America and seems likely to be causing an epidemic of birth defects especially in Brazil, will spread throughout the Americas. PAHO, which is a regional office of the World Health Organization, said:

There are two main reasons for the virus’s rapid spread (to 21 countries and territories): (1) the population of the Americas had not previously been exposed to Zika and therefore lacks immunity, and (2) Aedes mosquitoes—the main vector for Zika transmission—are present in all the region’s countries except Canada and continental Chile.

PAHO anticipates that Zika virus will continue to spread and will likely reach all countries and territories of the region where Aedes mosquitoes are found.

Those “countries and territories where Aedes mosquitoes are found” include a good portion of the United States, as these maps from the Centers for Disease Control and Prevention demonstrate:

CDC maps of the ranges of two mosquito species that could transmit Zika virus.
CDC maps of the ranges of two mosquito species that could transmit Zika virus.
Graphic from CDC.gov, original here.

 

The recent history is this: In the summer of 1999, the New York City health department put together reports that had come in from several doctors in the city and realized that an outbreak of encephalitis was moving through the area. Eight people who lived in one neighborhood were ill, four of them so seriously that they had to be put on respirators; five had what their doctors described as “profound muscle weakness.”

Within a month, 37 people had been identified with the perplexing syndrome, which seemed be caused by a virus, and four had died. At the same time, veterinarians at the Bronx Zoo discovered an unusual numbers of dead birds: exotics, like flamingos, and city birds, primarily crows. Their alertness provided the crucial piece for the CDC to realize that a novel disease had landed in the United States: West Nile virus, which was well-known in Europe, but had never been seen in this country before.

West Nile is transmitted by mosquitoes in a complex interplay with birds. It began moving with both birds and bugs down the East Coast and then across the Gulf Coast. As it went, the CDC realized that the neurologic illness that marked the disease’s first arrival had not been a one-time event, but its own looming epidemic within the larger one. “Neuroinvasive” West Nile, which in its worst manifestations caused not transient encephalitis but long-lasting floppy paralysis that resembled polio — and sometimes killed — bloomed in the summer of 2002 east of the Mississippi, and then moved west in the years afterward as the disease exhausted the pool of the vulnerable.

The CDC’s maps showing the emergence of “neuroinvasive” West Nile virus disease from 2001 to 2004; areas in black had the highest incidence.
Graphic by Maryn McKenna using maps by the CDC; originals available here.

So far, so normal, for a newly arrived disease. But here’s where the story gets complicated. By the beginning of this decade, West Nile had become endemic in the lower 48 states. It is not a mysterious new arrival; it is a known, life-altering threat. Its risk waxes and wanes with weather and insect populations, but it has one simple preventative: not allowing yourself to be bitten by a mosquito.

And yet: Here are the CDC’s most recent maps of neuroinvasive West Nile—showing that people are still falling to its most dire complication, 14 years after it was identified.

The CDC's maps for 2011-2014 showing the incidence of "neuroinvasive" West Nile virus disease; areas in black had the highest incidence.
The CDC’s maps for 2011-2014 showing the incidence of “neuroinvasive” West Nile virus disease; areas in black had the highest incidence.
Graphic by Maryn McKenna using maps by the CDC; originals available here.

The point here is not that people are careless or unthinking; in the early years of West Nile, two of the victims were the husband of the CDC’s then director, and the chief of its mosquito-borne diseases division, who would have been well aware of the risks. (Both recovered fully.) The point is that always behaving in a manner that protects you from a mosquito bite—conscientiously, persistently, faultlessly emptying pots and puddles, putting on long sleeves and repellent, choosing when not to go outdoors—is very difficult to maintain.

Zika is not West Nile. Among other things, Zika is spread by many fewer species of mosquitoes — one or possibly two, compared to 65 for West Nile. And West Nile’s non-human hosts, birds, live in closer proximity to more of us than Zika’s, which appear to be non-human primates. But though the rare, deadly complications of West Nile virus infection are different from those of Zika, they are just as serious and life-altering — and yet we failed to protect ourselves from them. As Zika spreads, we can hope that is a lesson we learn in time.

Previous posts in this series:

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Tool-Using Parrots Use Pebbles to Grind Seashells

In the spring of 2013, Megan Lambert noticed the greater vasa parrots of Lincolnshire Wildlife Park doing something odd. They looked like they were licking the cockle shells that lined the floor of their outdoor enclosure. But when Lambert looked closer, she noticed that they were holding a pebble or date pit in their beaks, and rubbing these against the shells.

They were using tools.

Several birds can use tools. Woodpecker finches prise grubs from wood with twigs, New Caledonian crows do the same, Egyptian vultures drop rocks onto eggs to crack them open, and rooks can raise the water level of a pitcher by dropping stones into it, Aesop-style. But among the 300 species of parrot, tool use is relatively rare. Black palm cockatoos use rocks to drum on tree trunks, while hyacinth macaws use sticks to prise open nuts. The kea, a delightfully mischievous New Zealand parrot, can use and make tools in the lab, but no one knows if they do so naturally.

Thanks to Lambert’s observations, the greater vasa parrot joins this exclusive club. Native to Madagascar, the greater vasa is a bit of a goth parrot, eschewing the vibrant hues of its relatives in favour of black and dark grey plumage. They’re sociable and inquisitive, and will often explore and manipulate objects in captivity; while watching them, Lambert saw one thread a twig through the open links of a chain. That seemed like play. By contrast, the thing with the seashells was probably more purposeful.

Seashells are made of calcium carbonate, and birds need calcium to build the shells of their eggs. Lambert thinks that the vasas were using the pebbles and pits to grind down the cockles and liberate the calcium within them. Other egg-laying animals, including sandwich terns and gopher tortoises, have been seen eating seashells, presumably for the same reason. But the vasas are the only ones known to process the shells. “That’s particularly interesting because humans are the only other animals known to use tools for grinding,” says Lambert.

But if that’s the case, why is it that only male parrots ground the seashells? If they’re trying to get at calcium for egg-laying, surely the females should be at it? Possibly, but during courtship and sex, vasa males spend a lot of time feeding females with regurgitated meals. Perhaps the calcium content of those fluids is a signal of the male’s quality as a mate?

Regardless, the behaviour is certainly common. Over a few months, Lambert saw all ten of the park’s greater vasa parrots interacting with the seashells, and at least five of them grinding the shells with pebbles or pits. One particular bird, a male named JD, was an especially prolific tool-user.

He was also a prolific tool-donor. On 16 occasions, Lambert saw one of the female parrots nicking a tool from another—usually JD, who tolerated the “theft”. “It’s quite unique that tools are transferred directly between birds, as this is not commonly observed in the animal kingdom and may provide clues as to how this behaviour came about in the first place,” says Lambert.

So far, Lambert and her colleagues haven’t done any experiments with the parrots, which leaves a lot of unanswered questions. Do the birds learn to use the tools themselves, or do they pick it up from their peers? What’s the purpose of the behaviour, and does it actually influence the birds’ reproductive success? Do the parrots grind seashells, or use other tools, in the wild? And what else are these animals capable of?

Paleo Profile: The Smoke Hill Bird

Photo by Brian Switek.
Hesperornis, restored at the New Mexico Museum of Nature and Science, was a cousin of the newly-named Fumicollis. Photo by Brian Switek.

During the late 19th century, as paleontologists were starting to uncover an array of prehistoric species that evolutionary theory predicted must have existed, ancient birds from the Cretaceous rock of Kansas became a scientific sensation. These were birds with teeth. The pair of them – dubbed Ichthyornis and Hesperornis by Yale’s Othniel Charles Marsh – underscored that birds evolved from toothy reptilian ancestors (which we now know were dinosaurs akin to Velociraptor).

Not that the archaic avians have always been popular. Upon seeing the government-funded monograph on the birds Marsh produced, penny-pinching congressmen turned “Birds with teeth!” as an incredulous cost-cutting rallying cry. And while the birds still show up in museums, they’re often overshadowed by their fuzzy non-avian relatives among the Dinosauria. Among a few others, however, paleontologists Alyssa Bell and Luis Chiappe have been taking a new look at these toothed birds, and, in fact, they’ve found a new one.

The new old bird, dubbed Fumicollis hoffmani by Bell and Chiappe, was one of these hesperornithiforms. These were loon-like diving birds that paddled through a now-vanished sea that washed over the midsection of North America. And, for a prehistoric bird, there’s actually quite a bit of Fumicollis to study. The vertebrae, hip pieces, and legs of the diver, originally excavated in 1937 and assigned to a different bird called Baptornis, allowed Bell and Chiappe to distinguish Fumicollis from other related birds.

All of a sudden the ancient environment preserved by the Smoky Hill Chalk is starting to look a little crowded. At least four different hesperornithiform birds, including Fumicollis, have been found in an upper section of the deposit that spans about five million years. That’s still a lot of time, and perhaps the birds were temporally separated. But what if they were actually ecological neighbors? If this were the case, Bell and Chiappe write, then the distribution of toothy diving birds through time and space might have been similar to what’s seen among modern penguins – a variety of species of different size classes could have partitioned the habitat, with some being deep divers and others foraging closer to the surface. If you were to plop into the waters of Kansas around 85 million years ago, and weren’t immediately eaten by a mosasaur, you may have been greeted by a diverse aviary of grinning birds.

The diversity of hesperornithiforms. From Bell and Chiappe, 2015.
The diversity of hesperornithiforms. From Bell and Chiappe, 2015.

Fossil Facts

Name: Fumicollis hoffmani

Meaning: Fumicollis is Latin for “smoke hill”, in reference to the Smoky Hill Member of the formation in which the bird was found, and the species name hoffmani honors museum donors Karen and Jim Hoffman.

Age: Around 85 million years old.

Where in the world?: Logan County, Kansas.

What sort of critter?: A toothed diving bird technically known as a hesperornithiform.

Size: About the size of a modern loon or grebe.

How much of the creature’s body is known?: Eight vertebrae, rib gragments, elements of the hips, parts of the right leg and foot, and a nearly-complete left leg.

Reference:

Bell, A., Chiappe, L. 2015. Identification of a new hesperornithiform from the Cretaceous Niobrara Chalk and implications for ecological diversity among early diving birds. PLOS ONE. doi: 10.1371/journal.pone.0141690

Previous Paleo Profiles:

The Unfortunate Dragon
The Cross Lizard
The South China Lizard
Zhenyuan Sun’s dragon
The Fascinating Scrap
The Sloth Claw
The Hefty Kangaroo
Mathison’s Fox
Scar Face
The Rain-Maker Lizard
“Lightning Claw”
The Ancient Agama
The Hell-Hound
The Cutting Shears of Kimbeto Wash
The False Moose
“Miss Piggy” the Prehistoric Turtle
Mexico’s “Bird Mimic”
The Greatest Auk
Catalonia’s Little Ape
Pakistan’s Butterfly-Faced Beast
The Head of the Devil
Spain’s Megatoothed Croc

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How a 5-Ounce Bird Stores 10,000 Maps in Its Head

It weighs only four or five ounces, its brain practically nothing, and yet, oh my God, what this little bird can do. It’s astonishing.

Photograph by Diana Tomback
Photograph by Diana Tomback

Around now, as we begin December, the Clark’s nutcracker has, conservatively, 5,000 (and up to 20,000) treasure maps in its head. They’re accurate, detailed, and instantly retrievable.

A Clark's nutcracker with a thought bubble full of maps
Photograph by Glenn Bartley, Alamy; Maps courtesy of jaffne, Flickr; GIF by Becky Harlan

It’s been burying seeds since August. It’s hidden so many (one study says almost 100,000 seeds) in the forest, meadows, and tree nooks that it can now fly up, look down, and see little x’s marking those spots—here, here, not there, but here—and do this for maybe a couple of miles around. It will remember these x’s for the next nine months.

How does it do it?

32 Seeds a Minute

It starts in high summer, when whitebark pine trees produce seeds in their cones—ripe for plucking. Nutcrackers dash from tree to tree, inspect, and, with their sharp beaks, tear into the cones, pulling seeds out one by one. They work fast. One study clocked a nutcracker harvesting “32 seeds per minute.”

These seeds are not for eating. They’re for hiding. Like a squirrel or chipmunk, the nutcracker clumps them into pouches located, in the bird’s case, under the tongue. It’s very expandable …

Drawing of one clark's nutcracker bird without seeds in its cheeks, and another clark's nutcracker with its cheeks full of seeds
Drawing by Robert Krulwich

The pouch “can hold an average of 92.7 plus or minus 8.9 seeds,” wrote Stephen Vander Wall and Russell Balda. Biologist Diana Tomback thinks it’s less, but one time she saw a (bigger than usual) nutcracker haul 150 seeds in its mouth. “He was a champ,” she told me.

Next, they land. Sometimes they peck little holes in the topsoil or under the leaf litter. Sometimes they leave seeds in nooks high up on trees. Most deposits have two or three seeds, so that by the time November comes around, a single bird has created 5,000 to 20,000 hiding places. They don’t stop until it gets too cold. “They are cache-aholics,” says Tomback.

When December comes—like right around now—the trees go bare and it’s time to switch from hide to seek mode. Nobody knows exactly how the birds manage this, but the best guess is that when a nutcracker digs its hole, it will notice two or three permanent objects at the site: an irregular rock, a bush, a tree stump. The objects, or markers, will be at different angles from the hiding place.

a drawing of clark's nutcracker looking at a tree stump and a mountain in the spring, with arrows pointing between the bird, the mountain, and the stump
Drawing by Robert Krulwich

Next, they measure. This seed cache, they note, “is a certain distance from object one, a certain distance from object two, a certain distance from object three,” says Tomback. “What they’re doing is triangulating. They’re kind of taking a photograph with their minds to find these objects” using reference points.

Psychologist Alan Kamil has a different view. He thinks the birds note the landmarks and remember not so much the distances, but the angles—where one object is in relation to the others. (“The tree stump’s 80 degrees south of the rock.”) These nutcrackers are doing geometry more than measuring.

a drawing of clark's nutcracker looking at a tree stump and a mountain in the rain, with arrows pointing between the bird, the mountain, and the stump
Drawing by Robert Krulwich

However they do it, when the snow falls and it’s time to eat, they’ll land at a site. “They will perch on a tree,” says Tomback, “on a low branch, [then light onto the ground, where] they pause, look around a bit, and they start digging, and in a few cases I’ll see them move slightly to the right or to the left and then come up again.”

She’s convinced that they’re remembering markers from summer or fall and using them to point to the X spot—and, “Lo and behold, these birds come up with their cracked seeds,” she says. “And it’s really pretty astounding.”

In the 1970s, Stephen Vander Wall ran a tricky little experiment. He shifted the markers at certain sites, so that instead of pointing to where the seeds actually were, they now pointed to where the seeds were not. Like this …

Picture of a clark's nutcracker standing between two X's and looking confused
Drawing by Robert Krulwich

And the birds, as you’d expect if they were triangulating, went to the wrong place.

But at sites where he left the markers untouched, the birds got it right. That’s a clue that each of these birds has thousands of marker-specific snapshots in their heads that they use for months and months. When the spring comes and the birds have their babies, they continue to visit old sites to gather seeds until their chicks fledge.

The mystery here, the deep mystery, is how do they manage to store so much data in their heads? I couldn’t possibly do what they do (I can’t even remember all ten digits in a phone number, so I’d be one very dead nutcracker in no time). Is their brain organized in some unique way?

Is their brain plastic? Can it grow more neurons or more connections when it needs to? Chickadees are also food hiders, and they do grow bushier brains when they need to, expanding in the “remember this” season and contracting afterward. Do Clark’s nutcrackers do that? We don’t know.

Whatever it is they do, I want what they’ve got.

Paleo Profile: The Greatest Auk

Auk body sizes. From Smith, 2015.
Auk body sizes. From Smith, 2015.

At nearly three feet tall and weighing ten pounds, the Great Auk was the bulkiest member of its family of seabirds. But, despite its name, it wasn’t the largest of all time. Between 8.7 and 4.9 million years ago, there was an even bigger auk.

The bird, named Miomancalla howardae by paleontologist N. Adam Smith in 2011, was found in the Pliocene rock of southern California. It didn’t belong to the same group as modern auks and murres – called alcids – but was on just the next branch over, fitting into a wider group called pan-alcids. A sort of proto-auk, in other words. And in a new analysis of how the body sizes of pan-alcids changed over time, Smith found that Miomancalla howardae significantly surpassed the famous Great Auk in size.

Drawing on data from living and fossil birds, Smith estimates that Miomancalla howardae weighed 11.8 pounds. That’s almost a pound and a half heavier than Smith’s estimate for the Great Auk, the next largest bird in the sample. Not all auks and their relatives were huge – Smith estimates that the extinct Miocepphus mergulellus was only about four ounces – but, within this ancient and varied family, Miomancalla howardae was the greatest auk.

A partial skeleton of Miomancalla howardae. From Smith, 2011.
A partial skeleton of Miomancalla howardae. From Smith, 2011.

Fossil Facts

Name: Miomancalla howardae

Meaning: Miomancalla indicates this genus includes relatives of the bird Mancalla that were around during the Miocene, while the species name honors zoologist Hildegarde Howard.

Age: Around 4 million years old.

Where in the world?: The Capistrano Formation of southern California.

What sort of critter?: A bird closely related to alcids, or auks.

Size: About three feet tall and 11.8 pounds.

How much of the creature’s body is known?: A partial skeleton including a skull, elements of the limbs, sternum, hips, and two vertebrae, as well as an isolated humerus.

References:

Smith, N. 2011. Taxonomic revision and phylogenetic analysis of the flightless Mancallinae (Aves, Pan-Alcidae). ZooKeys. doi: 10.3897/zookeys.91.709

Smith, N. 2015. Evolution of body mass in the Pan-Alcidae (Aves, Charadriiformes): the effects of combining neontological and paleontological data. Paleobiology. doi: 10.1017/pab.2015.24

Previous Paleo Profiles:

The Unfortunate Dragon
The Cross Lizard
The South China Lizard
Zhenyuan Sun’s dragon
The Fascinating Scrap
The Sloth Claw
The Hefty Kangaroo
Mathison’s Fox
Scar Face
The Rain-Maker Lizard
“Lightning Claw”
The Ancient Agama
The Hell-Hound
The Cutting Shears of Kimbeto Wash
The False Moose
“Miss Piggy” the Prehistoric Turtle
Mexico’s “Bird Mimic”

Giant Dinosaurs Nested Like Enormous Turkeys

All dinosaurs start off life small. That’s as true for today’s birds as the titans of the Mesozoic, and it may have been a critical part of what allowed ancient dinosaurs to surpass mammals in size. In order to hatch and grow into such stupendous shapes, though, the little egg-bound dinosaurs had to be nestled in a cozy little refuge. How did the biggest of the big care for their incubating little ones?

The classic image of a dinosaur on its nest is “Big Mamma.” Surrounded by elongated eggs, arms outstretched to protect them, the dinosaur was a model parent, even to the death. But this strategy wouldn’t have worked for huge, multi-ton dinosaurs, particularly the long-necked sauropods. These giants must have done something else to keep their broods safe and warm, and, according to paleontologist E. Martín Hechenleitner and colleagues, the solution may have anticipated what some modern dinosaurs do.

Nests of sauropod dinosaurs—particularly a subgroup called titanosaurs—have been found in Europe, Asia, India, and South America. These usually aren’t isolated finds. The giant dinosaurs congregated in vast nesting grounds, much like their ancestors did back at the dawn of the Jurassic. After digging out a nest, perhaps with the claws of their hind feet, the gravid dinosaurs squatted down to deposit their rounded eggs into the depression.

Titanosaurs didn’t just pick any old spot to lay their eggs, though. In Sanagasta, Argentina, for example, the dinosaurs chose to nest in a place dotted by active geothermal features that recall the geyser basins of Yellowstone—a natural source of heat—and an aggregation of 75 nests at another site in Spain suggests that titanosaurs were drawn to special spots on the landscape. And at locales where there wasn’t built-in heat, such as a nesting site in France, the dinosaurs may have collected decaying plant material to build mounds over their precious eggs.

A) Burrow nesting and B) mound nesting styles proposed for titanosaurs. From Hechenleitner et al., 2015.
A) Burrow nesting and B) mound nesting styles proposed for titanosaurs. From Hechenleitner et al., 2015.

If this sounds at all familiar, it’s because some modern birds use some of the same strategies. Megapodes, turkeys that live throughout Australasia, don’t sit on their nests, but find other ways to keep their eggs at their required temperature. For instance, Hechenleitner and coauthors write, the Malau megapode scratches nests over six feet deep into the soil to lay its eggs close to a source of geothermal heat. And while fossils of organic nest material have yet to be found at titanosaur nest sites, the microstructure of the eggshells and comparisons to the modern megapodes hint that some of the huge dinosaurs may have buried their eggs in mounds just like their living cousins do.

The titanosaurs probably weren’t model parents. The general view, at least at the moment, was that they were “lay ’em and leave ’em” dinosaurs, not providing anywhere near the care provided by Littlefoot’s mom. But neither were they dumb brutes that plopped eggs down wherever. Titanosaurs were picky dinosaurs that used the environment to raise their offspring during the critical early days. Watch a megapode scratched into the warm soil, and you’re seeing a glimmer of the Mesozoic moments that continued the dinosaurian reign for millions upon millions of years.

References:

Fowler, D., Hall, L. 2011. Scratch-digging sauropods, revisited. Historical Biology. doi: 10.1080/08912963.2010.504852

Hechenleitner, E., Grellet-Tinner, G., Fiorelli, L. 2015. What do giant titanosaur dinosaurs and modern Australasian megapodes have in common? PeerJ. doi: 10.7717/peerj.1341

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Should You Put a Baby Bird Back in the Nest? Depends If It’s Cute

Ah, the first days of summer—the smell of cut grass, kids on vacation… and baby birds falling out of trees.

Every year, I see a new flock of people rescuing fallen birds, and then arguing on Twitter and Facebook about whether it’s OK to put them back in the nest.

Some are adamant that if you handle a baby bird, its mother will reject it. Others say it’s fine; just put the bird back.

A lot of people face this dilemma at the beginning of summer, when many baby birds are taking their first flight from the nest—in bird-nerd speak, they’re fledging. I was in Mississippi in early June, and it seemed like it was raining dead baby birds there. One fell from its nest onto my car, and another mysteriously turned up on the porch steps. It was too late for those birds, but what do you do when faced with a little peeper like this?

First, you should ask yourself how cute the bird is.

Okay, that sounds cruel and judgmental. But it’s basically true. The Cornell Lab of Ornithology gives excellent advice: The first thing you need to know is whether the baby is a nestling or a fledgling. Most of the birds people find are fledglings. Fledglings have feathers, can hop, and are “generally adorable and fluffy, with a tiny stub of a tail.”

“When fledglings leave their nest they rarely return, so even if you see the nest it’s not a good idea to put the bird back in—it will hop right back out. Usually there is no reason to intervene at all beyond putting the bird on a nearby perch out of harm’s way and keeping pets indoors.”

And if you’ve got an ugly little unfeathered friend?

“If the baby bird is sparsely feathered and not capable of hopping, walking, flitting, or gripping tightly to your finger, it’s a nestling.

If you can find the nest (it may be well hidden), put the bird back as quickly as possible. Don’t worry—parent birds do not recognize their young by smell. They will not abandon a baby if it has been touched by humans.”

So leave the cute ones alone, and put the little ratty-looking ones back in the nest.

And if you don’t stumble across any fledglings this year, the Cornell Lab of Ornithology has a website where you can watch live video of baby birds on Birds Cams.

There are plenty of adorable Bird Cam moments, like this fledgling hawk returning to the nest and checking out the camera.


But it wasn’t all pretty. “This has been probably our toughest year on record,” says Charles Eldermire, who runs the Bird Cams program. The ospreys were hit by dime-sized hail a week before their eggs were to hatch, cracking all the eggs. A baby owl died, and the parents fed it to its siblings. Eldermire even had to put up warnings that viewers had to click on before watching particularly bad things happening.

“We started this project in part to help people learn about what happens in nature,” Eldermire says. “We’re aware that many have never had an unfiltered view of what happens in nature.”

The Bird Cam folks make a point of not interfering. “We can learn by letting it play out. Any intervention could have a negative impact; if we feed that baby owlet to save it, maybe it’s sick, or maybe the environment won’t support another barn owl.”

I love what Eldermire said next. Think about this as you watch the ospreys in the video above hunker over their eggs in a hailstorm: “The struggles that we go through as people in our own lives aren’t all that different from the animals on the screen.”

“The truth is we can’t control everything in our lives. One thing we can all learn from watching wild things and how they survive is that sense of resilience that is really at the core of any wild thing.”

The Echoes of Toothed Birds

Whenever I spot a grebe, I try to imagine the bird with teeth. This is another symptom of a chronically fossiliferous mind. You see, these snake-necked swimming birds have traditionally been taken as a proxy for a specific sort of ancient avian called hesperornithiforms. Best known by, as you might guess, Hesperornis – these toothed birds pioneered the diving lifestyle between 113 and 66 million years ago. Today’s grebes and loons look like edentulous echos of these lost Cretaceous days, or, as beautifully expressed by ornithologist William Beebe:

When in the depth of the winter, a full hundred miles from the nearest land, one sees a loon in the path of the steamer, listens to its weird, maniacal laughter, and sees it slowly sink downward through the green waters, it truly seems a hint of the bird-life of long-past ages.

No surprise, then, that paleontologists past sometimes considered loons and grebes to be the descendants of Hesperornis. Their bones carry the same superficial similarity. But this is an evolutionary ruse known as convergence. Loons and grebes are copycats that independently took up the same lifestyle as the toothed birds that dove after fish in warm Cretaceous seas and sometimes wound up in the stomachs of monstrous marine reptiles.

It takes an encyclopedic knowledge of anatomy to spot the differences, but the bones don’t lie. For example, as pointed out by Natural History Museum of Los Angeles paleontologists Alyssa Bell and Luis Chiappe in their new paper on Hesperornis and kin, loons, grebes, and the toothed birds all evolved different skeletal scaffolds for increasing their swimming power. Grebes have an expansion of the tibia for strong propulsive muscles, while loons split the space between a flange on their tibia and a kneecap. In the extinct toothed birds, however, the muscles mainly appear to have attached to a large, robust kneecap. Different anatomical solutions to the same mechanical problem.

The family tree of hesperornithiform birds created by Bell and Chiappe, 2015.
The family tree of hesperornithiform birds created by Bell and Chiappe, 2015.

From differences such as these, paleontologists have been able to discern that the hesperornithiformes are perched just outside the “modern” bird group – Neornithes to specialists – on the avian family tree. So far, so good. But as Bell and Chiappe point out in their paper, very little work has been done on sorting out the relationships of the various diving birds that snatched fish with snaggly jaws among the Northern Hemishphere’s Cretaceous waterways. With that in mind, the researchers cataloged 207 skeletal characteristics from 272 hesperornithiform specimens representing 18 different taxa to see who was related to whom.

After the various lineages grew or were pruned, Bell and Chiappe found that all the hesperornithiform birds created one group, and under this canopy there were several major branches. This is what allowed Bell and Chiappe to see how these birds became better and better adapted to lives spent at sea. Over time, the researchers point out, the birds show increasing specializations for better diving – such as a close connection of bone in the lower leg that allowed Hesperornis and other skilled swimmers to hold their toes close together during the recovery phase of a swim stroke, reducing drag and allowing them to get their feet in position for the next sweep faster.

Not that the story is one of straight-line progress from little flappy birds to flightless divers. Looking across the lineages, Bell and Chiappe found that these toothed birds evolved large body size at least three different times – in species of Brodavis and Pasquiaornis, as well as Hesperornis and its closest relatives. This might be a sign that each of these lineages were independently becoming adapted to being better divers. Bigger body size in diving animals, Bell and Chiappe point out, is related to larger lung capacity and the ability to better oxygenate the blood while paddling down deep. That means that even these toothy birds were copying each other before loons and grebes could continue the trend. In evolution, as with fashion and film, what’s old can be made new again.

Reference:

Bell, A., Chiappe, L. 2015. A species-level phylogeny of the Cretaceous Hesperornithiformes (Aves: Ornithuromorpha): implications for body size evolution amongst the earliest diving birds. Journal of Systematic Paleontology. doi: 10.1080/14772019.2015.1036141

The Call of the Terror Bird

When you think of a scary dinosaur, what comes to mind? The agile, sickle-clawed Utahraptor? A towering Tyrannosaurus? Something as alien as the croc-snouted, sail-backed Spinosaurus, perhaps? Books and museum halls are well-stocked with such Mesozoic nightmares, but scary dinosaurs have also stalked the land in the days after the end-Cretaceous mass extinction. There’s an entire group of fossil dinosaurs – technically known as phorusrhacids – that are imposing enough that paleontologists often call them by a more evocative name. These were the terror birds.

There aren’t any terror birds around today. The first evolved around 62 million years ago and the last perished about 2.5 million years ago, most of them playing the part of apex predator among the forests and plains of ancient South America. Their skeletons are evolutionary works of frightful beauty, and the latest to be described is the best-preserved terror bird ever seen.

A reconstruction of Llallawavis. The white elements are those that have been discovered. From Degrange et al., 2015.
A reconstruction of Llallawavis. The white elements are those that have been discovered. From Degrange et al., 2015.

Paleontologist Federico Degrange of Argentina’s Centro de Investigaciones en Ciences de la Tierra and colleagues named the old bird in the latest Journal of Vertebrate Paleontology. Drawing from Quechua and Latin, they’ve called it Llallawavis – the “magnificent bird”. It’s an apt title. Found in the 3.3 million year old rock of Argentina, Llallawavis is represented by a nearly-complete skeleton that includes the delicate bones of the middle ear, the bony ring of the eye, and ossified rings of the avian’s throat.

Aside from giving Degrange and coauthors a more detailed look the specific group of terror birds to which Llallawavis belonged – called mesembriornithines – the beautiful fossil adds some new details about how this 40 pound, 4-foot-tall carnivore interacted with the Pliocene world.

Thanks to the inner ear of Llallawavis, for example, the paleontologists were able to estimate that the terror bird had a relatively narrow range of hearing in the neighborhood of 3800 Hz. And since birds often vocalize in the lower ranges of what they can hear, Degrange and coauthors point out, this hints that Llallawavis may have communicated with low-frequency sounds that could travel long distances. Unfortunately, despite having part of the throat set in stone, the branches of the bird’s airway critical for sound-making were not fossilized to check what sounds they could have produced. What these impressive avians actually sounded like is still left to our imagination.

Reference:

Degrange, F., Tambussi, C., Taglioretti, M., Dondas, A., Scaglia, F. 2015. A new Mesembriornithinae (Aves, Phorusrhacidae) provides new insights into the phylogeny and sensory capabilities of terror birds. Journal of Vertebrate Paleontology. 35 (2). doi: 10.1080/02724634.2014.912656

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Easter Chicks: Cute, Fluffy, and Probably Bad For You

In the United States—and for that matter in much of the world—the foodborne disease Salmonella is a major public health problem. Here, it causes an estimated 1 million cases every year. We tend to think of those cases, and most foodborne illness, as minor episodes of needing to stay close to the bathroom—but every year, 19,000 of them end up in the hospital and almost 400 people die. And even if they survive, people aren’t necessarily out of danger; after decades of dismissing foodborne illness as unimportant and self-limited, researchers are beginning to understand that it can have lifelong consequences.

So it’s important, as much as possible, to identify the sources of Salmonella infection, and to alert people to the ways in which they can protect themselves.

And that’s why the Centers for Disease Control and Prevention, the CDC, is worried about those fluffball Easter chicks that might be appearing in households this weekend, as well as the juvenile poultry that backyard farmers and urban locavores may begin buying as the weather warms.

As I mentioned in my intro post yesterday, I also am writing for National Geographic‘s food site, The Plate, and I have a new post up there about the under-appreciated danger posed by live baby poultry. Whether you are buying them for immediate adorableness on top of an Easter basket, or eventual eggs or meat in a small-scale coop, most of us find baby chicks irresistible, in the hard-wired way that makes us melt before kittens and babies too. So we cradle them, and cuddle them, and smooch them on top of the head. But we forget that, just like babies of every other species, they are poop machines. And Salmonella travels in poop.

There are millions of baby chicks and other poultry sold every year: several millions pounds’ worth, according to the US Post Office, which ships most of them. In the past several years, they have caused significant outbreaks: 363 people in 43 states in 2014; 158 people ill, in 30 states in 2013; 195 people sick in 27 states in 2012; and 316 people sick in 43 states in the years before that.

This isn’t an argument against buying baby poultry, especially not if you’re doing it for small-scale egg or meat production. (Animal welfare organizations urge not buying baby animals just for Easter, because of the likelihood they will be dumped.)

But it is a plea on behalf of something I’m probably going to be saying a lot as we go forward: Don’t forget to wash your hands.

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In Which I Visit a Penguin Experiment and Hilarity Ensues

A few months ago, I noticed a tweet from John Hutchinson, saying that he was going to London Zoo to study their penguins, and how they move. I’ve covered Hutchinson’s work before; it frequently involves ushering animals over force-plates. And since the animals in this case would be penguins, it was practically guaranteed that something amusing would happen. Because penguins. So, I tagged along, and then wrote about it for the New Yorker’s Elements blog. It’s my first piece for them. Here’s a taster:

The first penguin approached. With an agility that belied its bumbling demeanor, it leaped straight over the smaller force plates. The second penguin seemed more circumspect, pausing at length to examine the unfamiliar terrain. Matyasova lured it on with sprat, but a third penguin blundered forward, joining it on the large force plate—a four-footed, two-penguin chimera. Matyasova then tried putting a penguin directly on the plate: it stood still and pecked at the duct tape holding the corridor together. Fortunately, this was just a dry run, though it was clear that Hutchinson’s patience was being tested as much as his equipment. “It almost always takes a while for the animals to get used to what you want them to do,” he said. “They’ll get progressively more coöperative.”

When Did Dinosaurs Learn to Fly?

Birds are dinosaurs. That’s a fact underscored by dozens upon dozens of discoveries in the last 30 years. Free of the historic blinders that cast dinosaurs as monstrous reptiles, we’re now gaining an ever-greater appreciation for how bird-like Tyrannosaurus and its famous relations really were.

In fact, many traits we think as unique to birds evolved hundreds of millions of years ago. Reproduction by laying shelled eggs goes back to some of the first vertebrates to carve out a living on land, around 315 million years ago. Fluffy body coverings might go back to the earliest dinosaurs. And air sacs that radiate out from the respiratory system into bone go back to the last common ancestor of dinosaurs like Apatosaurus and Allosaurus, at least.

But what about flight? More than anything else, the ability to take to the air seems to distinguish birds from most of the extinct dinosaurs, and this is where the picture starts to get a little fuzzy. For symbolic reasons, at least, avian flight marks the arrival of something new and different on the evolutionary scene, and paleontologists have spent over a century trying to tease out the transition.

The latest entry into the field was just published by Yale University researchers Teresa Feo, Daniel Field, and Richard Prum. They focused on one particular part of dinosaurian anatomy – asymmetrical feathers.

The presence of asymmetrical wing feathers – with a short leading edge and longer trailing edge, such as the primaries on the wing – has often been taken as a rough proxy for some kind of flying behavior in extinct, feathered creatures. That’s because this shape helps create lift. As Feo and colleagues point out, though, associating a general shape with the ability to fly is too coarse an interpretation. Many flightless birds have asymmetrical feathers that they inherited from their flying ancestors, including streamlined penguins that flap through the water. In order to tease out the clues of how these feathers contributed to flight, researchers have to comb over the plumage in closer detail.

Feo, Field, and Prum looked to geometry to see how the feathers of non-avian dinosaurs like Microraptor compared to those of early birds, such as Archaeopteryx, and their living relatives. Specifically, the researchers zeroed-in on the angles and lengths of asymmetrical feather barbs – the shafts that run perpendicular to the central rib that the rest of the feather branches out from. Given that the length and the angle of the feather barbs alter flight ability, Feo and coauthors could come up with a better idea of how skilled extinct dinosaurs would have been in the air.

The evolution of primary feather geometry. From Feo et al., 2015.
The evolution of primary feather geometry. From Feo et al., 2015.

In some ways, the primaries of Archaeopteryx and Microraptor were like those of other birds, including living species. The barbs on the “cutting edge” of their feathers were held at small angles relative to the shaft they branched from. This kept the leading edge of the feather relatively rigid and better for pitch control. But, on the trailing edges of their feathers, Archaeopteryx and Microraptor were different from flying birds.

Along the trailing edge of the primaries, Feo and coauthors point out, the barbs of flying birds are positioned at relatively large angles. This helps gives the feathers flexibility and maintain a stable airfoil. But in Archaeopteryx and Microraptor, the trailing-edge barbs were held at small angles. This kept their primaries stiff and less responsive, limiting their degree of flight control.

From their fossil sample, Feo and colleagues hypothesize that “modern” asymmetrical feathers with small leading and trailing barb angles first evolved in early, toothed birds like Confuciusornis and Eopengornis, around 125 million years ago. Along with other traits that evolved around the same time – such as a “winglet” called the alula and expanded bony keel – the barb angles hint that these birds really were flying.

But what about Archaeopteryx and Microraptor? Paleontologists have gone back and forth over whether or not these dinosaurs could fly for years. The emerging consensus is that they were able to move through the air somehow, but perhaps not in a way that would be familiar to us. While they weren’t capable of the “modern avian flight stroke” – the crux of these investigations – Archaeopteryx and Microraptor may have used some combination of gliding and flapping. Watching an airborne Archaeopteryx must have been quite a sight, and, from feather and bone, that is exactly what many paleontologists are trying to envision.

Reference:

Feo, T., Field, D., Prum. R. 2015. Barb geometry of asymmetrical feathers reveals a transitional morphology in the evolution of avian flight. Proceedings of the Royal Society B. doi: 10.1098.rspb.2014.2864