Flamingos depend on plant-derived chemical compounds to color their feathers, legs and beaks. Photo: Flickr user longhorndave

Pop quiz: Why are flamingos pink?

If you answered that it’s because of what they eat—namely shrimp—you’re right. But there’s more to the story than you might think.

Animals naturally synthesize a pigment called melanin, which determines the color of their eyes, fur (or feathers) and skin. Pigments are chemical compounds that create color in animals by absorbing certain wavelengths of light while reflecting others. Many animals can’t create pigments other than melanin on their own. Plant life, on the other hand, can produce a variety of them, and if a large quantity is ingested, those pigments can sometimes mask the melanin produced by the animal. Thus, some animals are often colored by the flowers, roots, seeds and fruits they consume

Flamingos are born with gray plumage. They get their rosy hue pink by ingesting a type of organic pigment called a carotenoid. They obtain this through their main food source, brine shrimp, which feast on microscopic algae that naturally produce carotenoids. Enzymes in the flamingos’ liver break down the compounds into pink and orange pigment molecules, which are then deposited into the birds’ feathers, legs and beaks. If flamingos didn’t feed on brine shrimp, their blushing plumage would eventually fade.

In captivity, the birds’ diets are supplemented with carotenoids such as beta-carotene and and canthaxanthin. Beta-carotene, responsible for the orange of carrots, pumpkins and sweet potatoes, is converted in the body to vitamin A. Canthaxanthin is responsible for the color of apples, peaches, strawberries and many flowers.

Shrimp can’t produce these compounds either, so they too depend on their diet to color their tiny bodies. Flamingos, though, are arguably the best-known examples of animals dyed by what they eat. What others species get pigment from their food? Here’s a quick list:

Northern cardinals and yellow goldfinches: When these birds consume berries from the dogwood tree, they metabolize carotenoids found inside the seeds of the fruit. The red, orange and yellow pigments contribute to the birds’ vibrant red and gold plumage, which would fade in intensity with each molt if cardinals were fed a carotenoid-free diet.

Salmon: Wild salmon consume small fish and crustaceans that feed on carotenoid-producing algae, accumulating enough of the chemical compounds to turn pink. Farmed salmon are fed color additives to achieve a deeper shades of red and pink.

Nudibranchs: These shell-less mollusks absorb the pigments of their food sources into their normally white bodies, reflecting the bright colors of sponges and cnidarians, which include jellyfish and corals.

Canaries: The birds’ normal diet doesn’t alter the color of its yellow feathers, but they can turn a deep orange if they regularly consume paprika, cayenne or red pepper. These spices each contain multiple carotenoids responsible for creating and red and yellow.

Ghost ants: There’s not much more than meets the eye with ghost ants: these tropical insects get their name from their transparent abdomens. Feed them water mixed with food coloring and watch their tiny, translucent lower halves fill up with brilliantly colored liquid.

Ghost ants sip sugar water with food coloring, which is visible in their transparent abdomens. Photo by Mohamed Babu/Solent News/Rex F/AP Images

Humans: Believe it or not, if a person eats large quantities of carrots, pumpkin or anything else with tons of carotenoids, his or her skin will turn yellow-orange. In fact, the help book Baby 411 includes this question and answer:

Q: My six-month-old started solids and now his skin is turning yellow. HELP!

A: You are what you eat! Babies are often first introduced to a series of yellow vegetables (carrots, squash, sweet potatoes). All these vegetables are rich in vitamin A (carotene). This vitamin has a pigment that can collect harmlessly on the skin, producing a condition called carotinemia.

How to tell that yellow-orange skin isn’t an indication of  jaundice? The National Institutes of Health explain that “If the whites of your eyes are not yellow, you may not have jaundice.”

Roosters have an internal circadian rhythm, which keeps them crowing on schedule even when the lights are turned off. Image via Wikimedia Commons/Muhammad Mahdi Karim

Some scientists investigate the universe’s biggest mysteries, like the Higgs boson, the mysterious particle that endows all other subatomic particles with mass.

Other researchers look into questions that are, well, a bit humbler—like the age-old puzzle of whether roosters simply crow when they see light of any kind, or if they truly know to crow when the morning sun arrives.

Lofty or not, it’s the goal of science to answer all questions that arise from the natural world, from roosters to bosons and everything in between. And a new study by Japanese researchers published today in Current Biology resolves the rooster question once and for all: The birds truly do have an inner circadian rhythm that tells when to crow.

The research team, from Nagoya University, investigated via a fairly straightforward route: They put several groups of four roosters in a room for weeks at a time, turned the lights off, and let a video camera running. Although roosters can occasionally crow at any time of day, the majority of their crowing was like clockwork, peaking in frequency at time intervals roughly 24 hours apart—the time their bodies knew to be morning based on the sunlight they’d last seen before entering the experiment.

This consistency continued for about 2 weeks, then gradually began to die out. The roosters were left in the room for 4 weeks in total, and during the second half of the experiment, their crowing began occurring less regularly, at any time of day, suggesting that they do need to see the sun on a regular basis for their circadian rhythms to function properly.

In the experiment’s second part, the researchers also subjected the roosters to alternating periods of 12 hours of light and 12 hours of darkness, while using bright flashes of light and the recorded crowing of roosters (since crowing is known to be contagious) to induce crowing at different times of day. When they activated these stimuli near at or near the dawn of the roosters’ 12-hour day, crowing rates increased significantly. At other times of day, though, exposing them to sudden flashes of light or playing the sound of crowing had virtually no effect, showing that the underlying circadian cycle played a role in the birds’ response to the stimuli.

Of course, many people who live in close proximity to roosters note that they often crow in response to a random light source turning on, like a car’s headlights, no matter what time of day it is. While this may be true, the experiment shows that the odds of a rooster responding to a car’s headlights depend on how close the current time is to dawn—at some level, the rooster’s body knows whether it should be crowing or not, and responding to artificial stimuli based on this rhythm.

For the research team, all this is merely a prelude to their bigger, more complex questions: Why do roosters have a biological clock that controls crowing in the first place, and how does it work? They see the simple crowing patterns of the rooster as an entry point into better understanding the vocalizations of a range of animals. “We still do not know why a dog says ‘bow-wow’ and a cat says ‘meow,’” Takashi Yoshimura, one of the co-authors, said in a press statement. “We are interested in the mechanism of this genetically controlled behavior and believe that chickens provide an excellent model.”

A fossil of a prehistoric bird from the enantiornithine genus shows feathers on its hind legs—evidence of an extra pair of wings. Courtesy of Xiaoting Zheng et al/Science

Roughly 150 million years ago, birds began to evolve. The winged creatures we see in the skies today descended from a group of dinosaurs called theropods, which included tyrannosaurs, during a 54-million-year chunk of time known as the Jurassic period. Why the ability to fly evolved in some species is a difficult question to answer, but scientists agree that wings came to be because they must have been useful: they might have helped land-based animals leap into the air, or helped gliding creatures who flapped their arms produce thrust.

As researchers continue to probe the origin of flight, studies of fossils have shown that theropods–particularly coelurosaurian dinosaurs, which closely resemble modern birds—had large feathers on both their fore limbs and hind limbs. However, extensive evidence for these leg feathers didn’t exist in the earliest birds. But now, a new examination of fossils reported today in the journal Science reveals several examples of this four-winged anatomy in modern birds’ oldest common ancestors.

Modern birds have two types of feathers: vaned feathers that cover the outside of the body, and the down feathers that grow underneath them. Researchers studying the approximately 120 million-year-old fossils of 11 primitive birds from the Shandong Tianyu Museum of Natural History in China found that one type of vaned plumage, also known as pennaceous feathers, was neatly preserved in skeletal fossils of these specimens, along each creatures’ hind limbs. After this find, the researchers must have been flying high: The feathers of birds’ wings, known as flight feathers, are long, stiff and asymmetrically shaped pennaceous feathers, similar to those found in the fossils. When fanned together, pennaceous feathers form the broad surfaces of birds’ wingspans—without these surfaces, birds cannot stay aloft.

Pennaceous feathers, which are composed of many flattened barbs, existed in some winged dinosaurs. Finding them on the hind legs of early birds suggests that before birds used two wings to fly, they may have depended on four. Over millions of years, however, birds gradually lost the feathers on this extra set of wings.

The study adds to existing theories that suggest the first birds flew with four wings. Examination of a primitive bird fossil from the Archaeopteryx genus in 2004 revealed long feathers on the animal’s back and legs, which would have aided its gliding ability. Two years later, another study of the crow-sized animal, which lived about 150 million years ago, reported that the prehistoric bird’s feathers resembled those on modern birds’ flight wings.

One of the more complete skeletons examined in today’s study actually showed hind-limb pennaceous feathers along the bone of each leg. The longest feather stretched almost two inches, which is remarkable considering that the legs they covered were between one inch and two and a half inches long. In fact, specimens from a group of birds called Enantiornithes, which externally resemble modern birds, showed symmetrically paired large feathers preserved along their hind leg bones. Such feather arrangement is present in modern birds’ wings.

Researchers speculate that the second set of wings might have provided extra lift or created drag in the air. They might also have helped birds maneuver their airborne bodies.

If these hind wings indeed served a functional purpose in fight, they will earn an important place in bird evolution. Bird movement is characterized by a combination of feathered arms for flight and legs for walking on land. This study suggests that if walking legs, present in birds today, developed after these feathered hind legs, then the loss of feathers on the back legs—and thus an extra pair of wings—reflects a period of change during which the arms became specialized for flight and the legs, for locomotion.

Today, leg feathers are less well developed than wing feathers—they are usually much smaller and fluffy—and they serve as protection and insulation for the leg. These fluffy bits are sparse too—instead, the legs are covered in scales, which form only if feather growth is inhibited. Studies of modern birds show how this works. As chicks develop from embryos and grow into adults, feathered legs can be transformed into scaled legs, or vice versa, by altering how certain genes are expressed.

The recent revelation about feathers on birds’ hind legs suggest that a similar genetic, and more permanent, change might have occurred early in bird evolution, according to lead researchers. This shift triggered the loss of birds’ hind wings, pushing the creatures down an evolutionary path that would allow them to fly with just two.

Scientists discovered that the penguins plumage is even colder than the surrounding air, potentially allowing them to absorb heat through convection. Image © Université de Strasbourg and Centre National de la Recherche Scientifique (CNRS), Strasbourg, France

Antarctica, as you might expect, gets pretty darn cold: Temperatures as low as -40 degrees Fahrenheit are often recorded during the winter. For the creatures who live there, this extreme cold demands innovative survival strategies that enable the loss of as little heat as possible.

Scientists recently discovered that Emperor Penguins—one of Antarctica’s most celebrated species—employ a particularly unusual technique for surviving the daily chill. As detailed in an article published today in the journal Biology Letters, the birds minimize heat loss by keeping the outer surface of their plumage below the temperature of the surrounding air.

At the same time, the penguins’ thick plumage insulates their body and keeps it toasty. A team of scientists from Scotland and France recently came to the finding by analyzing thermal images (below) of penguins taken at a coastal Emperor breeding colony in Adélie Land, an area of Antarctica claimed by France.

The research drew upon theromgraphic images of the penguins collected in the wild. Image © Université de Strasbourg and Centre National de la Recherche Scientifique (CNRS), Strasbourg, France

The researchers analyzed thermographic images like this one taken over roughly a month during June 2008. During that period, the average air temperature was 0.32 degrees Fahreinheit. At the same time, the majority of the plumage covering the penguins’ bodies was even colder: the surface of their warmest body part, their feet, was an average 1.76 degrees Fahrenheit, but the plumage on their heads, chests and backs were -1.84, -7.24 and -9.76 degrees Fahrenheit respectively. Overall, nearly the entire outer surface of the penguins’ bodies was below freezing at all times, except for their eyes and beaks.

The scientists also used a computer simulation to determine how much heat was lost or gained from each part of the body—and discovered that by keeping their outer surface below air temperature, the birds might paradoxically be able to draw very slight amounts of heat from the air around them. The key to their trick is the difference between two different types of heat transfer: radiation and convection.

The penguins do lose internal body heat to the surrounding air through thermal radiation, just as our bodies do on a cold day. Because their bodies (but not surface plumage) are warmer than the surrounding air, heat gradually radiates outward over time, moving from a warmer material to a colder one. To maintain body temperature while losing heat, penguins, like all warm-blooded animals, rely on the metabolism of food.

The penguins, though, have an additional strategy. Since their outer plumage is even colder than the air, the simulation showed that they might gain back a little of this heat through thermal convection—the transfer of heat via the movement of a fluid (in this case, the air). As the cold Antarctic air cycles around their bodies, slightly warmer air comes into contact with the plumage and donates minute amounts of heat back to the penguins, then cycles away at a slightly colder temperature.

Most of this heat, the researchers note, probably doesn’t make it all the way through the plumage and back to the penguins’ bodies, but it could make a slight difference. At the very least, the method by which a penguin’s plumage wicks heat from the bitterly cold air that surrounds it helps to cancel out some of the heat that’s radiating from its interior.

And given the Emperors’ unusually demanding breeding cycle (celebrated in the documentary March of the Penguins), every bit of warmth counts. Each winter, they trek from inland coastal locations to the coast inland—walking as far as 75 miles—where they breed and incubate their eggs. After the females lay eggs, the males incubate them by balancing them on top of their feet in a pouch for roughly 64 days. Since they don’t eat anything during this entire period, conserving calories by giving up as little heat as possible is absolutely crucial.

Photo by Philippe Verbelen

Indonesia’s numerous islands (18,307 to be exact) house a wealth of avian biodiversity, yet scientists speculate that many of the country’s bird species have yet to be discovered or categorized. But ornithologists are celebrating today as a new species of owl joins the list, taking filling in one more spot in the catalog of the archipelago’s animals.

In 2003, George Sangster, a Dutch ornithologist from Stockholm University, and his wife were exploring the forested foothills of Lombak, an island just east of Bali. While traipsing through the forest at night, Sangster picked up on an owl call he did not recognize. Coincidentally, just a few days later Ben King, an ornithologist from the American Museum of Natural History, heard those same calls from the jungle and also suspected they came from an unknown species.

“It was quite a coincidence that two of us identified this new bird species on different parts of the same island, within a few days of being on the island, especially considering that no-one had noticed anything special about these owls in the previous 100 years,” Sangster said in a statement.

Locals on Lombak, it turned out, were familiar with the species. Known as burung pok–roughly translated as “pook,” a mimic of the owl’s hoots–the birds turned out to be a common feature of the nocturnal landscape. But locals on neighboring islands, however, said they had never heard of the bird and did not recognize its unusual call.

Here, you can hear the little Indonesian owl hooting into the night, which the researchers describe as “a single whistle without overtones:

Although birders and scientists alike love owls, surprisingly not much is known about those species’ biology, including how they relate to one another on an evolutionary scale. Lately, however, researchers have been working double time to get a grip on owls. In 1975, for example, scientists knew of 146 species, and that number leapt to 250 as of 2008. One driver behind this jump in species numbers was the realization that owl calls could lend clues (PDF) to classifying different types of owls. Owls hoot to attract mates and recognize one another as the same, so animals evolved calls unique to their species. In some cases, owls previously classified as the same species were split in two primarily on the basis of their calls.

Sangster, King and two other researchers from Sweden and Australia got together and were able to photograph the owls by playing back recordings of the call to attract several of the hooting culprits. Digging through old records, the researchers found that the owls matched specimens collected back in 1896 by Alfred Everett, a British administrator who was based in Borneo and spent his spare time collecting natural history curios. That same year, Ernest Hartlet, a naturalist who reported on Everett’s field work, accurately noted that “the cry is a clear but not very loud ‘pwok,’ like that of [O.] lempiji, but somewhat different in tone.”

Though Hartlet and Everett came close to identifying the new species, they fell just short of making the leap. Since then, no one had collected or observed this type of owl, according to records from the American Museum of Natural History and the Natural History Museum at Tring, in the U.K. 

All of this evidence, the team concluded in a PLoS ONE paper, pointed to the discovery of a new species of owl.

Because the new owl shows dramatically less individual variation to its brown and cream-speckled feather patterns than similar species found on neighboring islands, the scientists hypothesize that ancestors of the Lombok owls may have been isolated and trapped on their island many years before by a catastrophic volcanic eruption. Starting with just a handful of individuals, the animals then could have slowly rebuilt their populations, eventually evolving into a unique lineage.

The species, they report, is the first bird known to be unique to Lombok. The authors named the new bird Otus jolandae, after Sangster’s wife, Jolanda.

The Indian Peafowl may need help adapting to climate change. Photo by Sergiu Bacioiu

In the coming years, the birds of Asia’s Eastern Himalaya and Lower Mekong Basin, considered biodiversity hotspots by scientists, will need to relocate within the region to find viable habitat, according to a new study published in the journal Global Change Biology. The reason? Climate change. Researchers at England’s Durham University tested 500 different climate-change scenarios for each of 370 Asian bird species and found that every possible climatic outcome–even the least extreme–would have an adverse effect on the birds.

The researchers honed in on sensitive habitat in Bhutan, Laos, Cambodia, Vietnam and parts of Nepal and India, where development and population growth are occurring at a rapid clip and the effects of climate shifts are expected to be significant, with both wet and dry seasons intensifying. Portions of the region will suffer drastically, the study authors wrote, and certain climates will have “no present-day analogues” by 2100.

This will send birds in search of food. “Food availability [could become] more seasonal, meaning that in some periods there is an over-abundance of food, in others the birds starve,” lead author Robert Bagchi, formerly of Durham University and now a senior scientist at ETH Zürich, told Surprising Science. Species in the Lower Mekong Basin, which includes Laos, Cambodia and Vietnam, will be most vulnerable to these shifts.

In the most extreme cases, the research showed, birds will need to be physically relocated–an outcome scientists are hoping to avoid. Instead, they’re recommending proactive conservation. “Maintaining forest patches and corridors through agricultural landscapes is likely to be a far more effective and affordable long term solution than translocation,” Bagchi said. Linking bird habitat will be key so that species can move between sites that are currently viable and those that will suit them in the future.

The ramifications of bird relocation on plants and other animals has yet to be examined, but the shifts likely won’t bode well. Plant species that rely on birds to disperse seeds may not be able to survive, according to Bagchi. “Understanding how species interactions are going to change is very much at the cutting edge of what ecologists are trying to understand at the moment,” he said.

The study joins a growing body of research into how changes in climate affect food and water supplies, ranges, breeding habits and life cycles for birds and a variety of wildlife. Among those studied and deemed at risk are California’s threatened and endangered bird species. Research published last year showed that sea-level rise and changes in precipitation will most seriously imperil wetlands birds.

Investigators with the National Science Foundation are currently studying the prospects of Antarctica’s Adélie penguins for surviving climate change; the birds rely on floating sea ice, and if warmer temperatures melt that ice, the penguins will vanish. The top swimmers and foragers among their ranks have the best chances of survival, according to researchers, whose work is detailed in this video.

Scientists in Antarctica are studying how climate change is affecting Adélie penguins. Photo by Penguinscience.com

Among mammals, the adverse impacts of global warming on polar bear habitat has been well documented. A 2011 study showed the bears must swim longer distances in search of stable sea ice and that cubs are 27 percent more likely to die as a result of the extended plunges. New research published in the journal Ecology reveals that elephants are also vulnerable: Higher temperatures and lower precipitation have created an acute threat to Myanmar’s endangered Asian elephants, particularly babies.

Land-dwelling North American animals have also been affected. The snowmelt required by wolverines for reproduction is so greatly diminished that federal wildlife officials nominated the animal for Endangered Species Act listing earlier this month. And climate-change-induced, late-spring snowfalls have caused the Columbian ground squirrel to extend its Rocky Mountains hibernation by ten days over the past 20 years, according to Canadian researchers. By emerging later, the animals lose valuable time to stock up on the food they need to survive the next winter.

Conversely, another hibernator, the yellow-bellied marmot, was shown in a 2010 study to actually thrive in the face of climate alterations–a phenomenon scientists attributed to earlier-spring plant growth. But they predicted the benefits would be short-lived due to an increasingly serious climatic pitfall: drought.

Meanwhile, as temperatures continue to rise, other wildlife and insects are expected to flourish outright, including certain invasive species that will be able to expand their ranges and survive winters in new places, as well as non-invasive species. A recent Discovery news article highlighting climate-change winners focused on the brown argus butterfly, which has found a new host plant and a larger range; the albatross, whose food-finding ability has gotten a boost from shifting wind patterns; and the Australian gray nurse shark, whose population could boom if warmer waters reunite two separate populations. Also, melting Arctic ice could provide new feeding opportunities for orcas–but if so, two species it preys on, belugas and narwhals, would move into the climate-change losers column.

A feral cat, just trying to get by. Photo: Topsynette

There are so many ways for a little bird or squirrel to die these days–they can be squished by cars, splattered into buildings, run over by bulldozers, poisoned or even shot. But if you have ever had to clean up a mangled “present” left on your doorstep by a kitty, you’ll know that little creatures can also be killed by pets.

Cats in particular have earned a nasty reputation for themselves as blood thirsty killers of wildlife. They have been named among the top 100 worst invasive species (PDF) in the world. Cats have also earned credit for countless island extinctions. Arriving onto the virgin specks of land alongside sailors, the naive native fauna didn’t stand a chance against these clever, efficient killers. All said, cats claim 14 percent of modern bird, amphibian and mammal island extinctions. But what about the mainland?

A recent study aimed to find out just that. Now the stats are in, and it’s much worse than we thought. But before bird lovers rush to declaw pets, the study’s scientists also found that feral cats and strays–not house cats–are responsible for the majority of the killings.

To arrive at the new findings, researchers from the Smithsonian’s Migratory Bird Center and the U.S. Fish and Wildlife Center assembled a systematic review of every U.S.-based cat predation study known in the scientific literature (excluding Hawaii and Alaska). Based on figures the authors verified as scientifically rigorous, they statistically quantified the total bird and small mammal mortality estimate caused by cats, further breaking the categories down into domestic versus unowned cats, that latter of which the authors define as barnyard kitties, strays that receive food from kind humans and cats that are completely wild. 

Their results paint a grim picture for wildlife. In a paper published today in Nature Communications, they write that between 1.4 to 3.7 billion birds lose their lives to cats each year in the United States. Around 33 percent of the birds killed are non-native species (read: unwelcome). Even more startlingly, between 6.9 to 20.7 billion small mammals succumb to the predators. In urban areas, most of the mammals were pesky rats and mice, though rabbit, squirrel, shrew and vole carcasses turned up in rural and suburban locations.  Just under 70 percent of those deaths, the authors calculate, occur at the paws of unowned cats, a number about three times the amount domesticated kitties slay.

Cats may also be impacting reptile and amphibian populations, although calculating those figures remains difficult due to a lack of studies. Based upon data taken from Europe, Australia and New Zealand and extrapolated to fit the United States, the authors think that between 258 to 822 million reptiles and 95 to 299 million amphibians may die by cat each year nationwide, although additional research would be needed to verify those extrapolations.

These estimates, especially for birds, far exceed any previous figures for cat killings, they write, and also exceed all other direct sources of anthropogenic bird deaths, such as cars, buildings and communication towers.

The authors conclude:

The magnitude of wildlife mortality caused by cats that we report here far exceeds all prior estimates. Available evidence suggests that mortality from cat predation is likely to be substantial in all parts of the world where free-ranging cats occur. 

Our estimates should alert policy makers and the general public about the large magnitude of wildlife mortality caused by free-ranging cats.

Although our results suggest that owned cats have relatively less impact than un-owned cats, owned cats still cause substantial wildlife mortality; simple solutions to reduce mortality caused by pets, such as limiting or preventing outdoor access, should be pursued.

The authors write that trap-neuter/spay-return programs–or those in which feral cats are caught, “fixed,” and released back into the wild unharmed–are undertaken throughout North American and are carried out largely without consideration towards to native animals and without widespread public knowledge. While cat lovers claim that these methods reduce wildlife mortality by humanely limiting the growth of feral colonies, the authors point out that the scientific literature does not support this assumption. Therefore, such colonies should be a “wildlife management priority,” they write. They don’t come out and say it but the implication is that feral cat colonies should be exterminated.

But feral cats, some animal rights advocates argue, are simply trying to eke out a living in a tough, unloving world. As the Humane Society explains, simply removing the cats may not be the most efficient means of solving the problem because cats that are inevitably left behind repopulate the colony, surrounding colonies may move in to replace the old and “the ongoing abandonment of unaltered pet cats…can also repopulate a vacated territory.” Feral cats, after all, are the “offspring of lost or abandoned pet cats or other feral cats who are not spayed or neutered.” Targeting irresponsible humans may provide a different solution, although spay/neuter laws are controversial. 

In Washington D.C. alone, for example, there are more than 300 known feral cat colonies. Wildlife are victims of this problem, but feral cats are too as conditions for survival are tough. And as with so many other environmental banes, the root of the problem neatly traces back to a single source: humans. As the authors write in their paper, feral cats are the single greatest source of anthropogenic (human-driven) mortality for U.S. birds and mammals.

Incidentally, the Humane Society will host World Spay Day on February 26. Find an event for your furry friend to attend, or even host a spaying party yourself. 

Each year, around 5,300 Golden Warblers – a threatened species – die from collisions with communication towers. Photo: Brian Small

Beneath massive communication towers, fallen bird bodies pile up like confetti. They collide with the steel structures—which can reach heights twice that of the Empire State Building—or fly into the miles of cables radiating around the beacons. Each year, nearly 7 million birds lose their lives to these web-like traps of wire and metal—27 times more birds than were killed in the infamous 1989 Exxon Valdez spill.

The killing season peaks during the time nocturnal migratory birds make their way between Canada and the U.S. Flying in the darkness, they spot the tower lights, become disoriented and begin circling the beams. After a storm, when natural navigational cues like the stars or moon are obscured, mortalities are particularly high.

While the magnitude of causalities is worrying, until now researchers did not know whether or not the avian victims were species of conservation concern or just common sparrows. Research recently published in the journal Biological Conservation, however, confirms scientists’ fears. Members of thirteen threatened North American species succumb each year to the towers. The fallen birds represent between 1 and 9 percent of those species’ total population numbers.

“Certain species of birds, including many already in decline, are killed at communication towers in far greater proportions than their abundance would suggest,” said lead author Travis Longcore, the science director of the Urban Wildlands Group and an associate professor of research at the Spatial Science Institute at the University of Southern California, in an email. “And it’s not just these thirteen species we have to worry about—they’re just the ones being killed at the highest rates,” he continued. “Many more species of concern are killed at lower rates, too.”

To figure out mortality by species and regions, Longcore and his co-authors constructed a database of species deaths based on verifiable, available records. Then, they calculated the mean proportion of each species killed and compared those statistics with overall mortality rates for each species’ total population in the U.S. and Canada.

All in all, they found, 97 percent of the birds being killed are passerines, or songbirds. Among the threatened birds that are dying are the Yellow Rail, with 2,200 annuals mortalities, representing 8.9 percent of the species’ total population; the Golden-winged Warbler, with 5,300 annual deaths, representing 2.5 percent of the population; and the Swainson’s Warbler, with 7,500 annual deaths, representing 8.9 percent of the population. Other species, though not currently of conservation concern, still suffer formidable losses. Red-eyed Vireos, for example, relinquish 581,000 lives to communication towers each year, and around 499,000 Ovenbirds die this way, too.

Last year, the same team found that around 1,000 of the towers, used for television and radio broadcast, are responsible for 70 percent of the bird deaths. Those 1,000 towers, the team noted, stand 900 feet or higher, representing the largest of North America’s 70,000-odd communication towers included in the original study. In their follow up study, they identified the deadliest sites, which are in Texas, Louisiana, Florida and the Midwest. The findings are no surprise; the Southeastern coastal plain and the Midwest regions contain the highest concentrations of the tallest towers on the continent.

The Migratory Bird Treaty Act of 1918 makes it illegal to kill migratory birds in the U.S., so the researchers hope their findings may be used to better regulate communication towers. Eliminating the steady-glow red lights from the towers and replacing them with blinking lights—the same fix adopted by the Federal Aviation Administration—may reduce bird mortality by 50 to 70 percent.

The study also carries another lesson, Longcore said. Simply counting up the total number of birds killed by wind turbines, cats, windows, pesticides or communication towers across the country and then making crude comparisons between mortality sources can be misleading, he pointed out. The most impactful data—the types of species killed, and where, and when and how—often lurk beneath those surface figures. “Simple estimates of total ‘bird’ mortality are insufficient; it matters which species are being killed,” he said. “Each mortality source may be significant, but for different species and in different places.”

Plastic debris and particles are now turning up in the ocean waters surrounding Antarctica. Image via Wikimedia Commons/Koyos

A little over two years ago, marine researchers set sail aboard the French schooner Tara as part of a plan to create the first comprehensive global picture of plankton ecosystems. By the time the journey concluded earlier this year, they had observed roughly 1 million previously unidentified species of plankton, giving an unprecedented window into the diversity of marine life at the most basic level of the food chain.

Unfortunately, the group’s findings weren’t all rosy. If, as they note, “studying plankton is like taking the pulse of our planet,” then Tara‘s journey also included the discovery of something like an irregular heartbeat. Last week, the researchers revealed that while collecting samples in the Southern Ocean (the waters that encircle Antarctica), they detected remarkably high levels of plastic pollutants in a habitat that was widely considered to be unspoiled.

“We had always assumed that this was a pristine environment, very little touched by human beings,” Chris Bowler, one of the team’s scientists, told The Guardian. ”The fact that we found these plastics is a sign that the reach of human beings is truly planetary in scale.”

The researchers expected to find some level of plastic in the waters, as all of the world’s oceans contain pieces of plastic debris—most are microscopic particles that result from the degradation of objects like plastic bags and bottles. But the team’s samples, collected from four different locations in the Southern Ocean and Antarctica, revealed concentrations of plastic far higher than they would have predicted: roughly 50,000 fragments per square kilometer, a figure that was considered a “high” amount just a couple of years ago but is now simply the world average for oceanic plastic concentration.  The group says that they had expected to find concentrations of plastic somewhere around 5,000 fragments per square kilometer in the remote waters near Antarctica.

Although the Great Pacific Garbage Patch is the most notorious area of concentrated waste debris in the ocean, the North Atlantic and North Sea are also home to high amounts of floating plastic and garbage. What makes the discovery of such debris near Antarctica such a concern is that, unlike these areas near Europe and Asia, the Southern Ocean is distant from most human activity, indicating just how far this type of pollution has spread over time.

“Discovering plastic at these very high levels was completely unexpected because the Southern Ocean is relatively separated from the world’s other oceans and does not normally mix with them,” Bowler said. It’s difficult to know exactly where the plastic in these waters originated, but based on ocean currents, the Tara researchers speculate that the majority came from Australia, Africa and South America.

Floating plastic debris harms wildlife in a number of ways. For birds and fish, larger pieces are mistaken for food, and consumption of enough plastic can be toxic. On the Midway Islands, nearby the Great Pacific Patch, researchers have determined that all 2 million resident Laysan albatrosses have some quantity of plastic in their stomach, and that about a third of albatross chicks die due to being mistakenly fed plastic by their parents.

Plastic found inside an albatross carcass on the Midway Islands. Image via U.S. Fish and Wildlife Service

On a smaller level, UV light and the salt in seawater cause microscopic particles of plastic to emit toxic chemicals such as PCBs and DDT. When ingested by many types of marine species, these can be mistaken for estradiol, a sex hormone, causing a variety of symptoms related to endocrine disruption. Additionally, the chemicals tend to bioaccumulate in organisms as they move up the food chain, and can eventually lead to tainted populations of fish that humans regularly consume.

These sorts of problems have led Charles Moore, an oceanographer and racing boat captain who played a significant role in discovering and publicizing the great Pacific Garbage Patch, to argue that plastic pollution has become a more urgent problem for ocean life than climate change. “The sad thing is we thought Antarctic waters were clean,” he told the Australian Associated Press after the Tara‘s findings were announced. ”We no longer have an ocean anywhere that is free of pollution.”

The crested ibis is one of the world’s most endangered bird species, but captive breeding programs might help it make a comeback. Image via Flickr user Andy_Li

In our October issue, Michelle Nijhuis joins wildlife biologists in searching Colorado’s caves and waterfalls for one of the world’s most mysterious bird species: the black swift. Although fewer than 100 breeding sites of the black swift are known, Nijhuis was lucky enough to see ornithologist Ron Torretta locate a black swift that had been geotagged in 2010, providing researchers with a cache of information about the wanderings of the enigmatic bird. Here are a few more of the most mysterious and elusive of the world’s bird species.

1. Night Parrot: Between 1912 and 1979, birders spotted this elusive species, native to the interior of Australia, exactly zero times—leading most scientists to believe it had gone extinct. Since then, a tiny handful of sightings of the nocturnal, yellow-green bird have occurred, and experts now estimate that the population is somewhere between 50 and 250 mature individuals. After the last verified sighting in November 2006, when park rangers in the state of Queensland turned up a decapitated specimen that had died after flying into a barbed-wire fence, the Australian government chose to keep the find temporarily secret while they searched for more night parrots, so as to avoid an influx of birders flooding the remote park in hopes of spotting one of the world’s rarest birds.

The Ribbon-tailed Astrapia has tail plumage three times its body length, the longest for any bird. Image via Wikimedia Commons/Marka Harper

2. Ribbon-tailed Astrapia: Endemic to the forest highlands of Papua New Guinea, this bird has the longest tail feathers (in relation to body size) of any bird species, with feathers three times its body length. Unfortunately, this stunning plumage has enticed poachers; hunting, along with habitat loss, has led to the species being listed as “near threatened” by the International Union for Conservation of Nature. The species, the most recent bird of paradise to be documented, was first described by explorer Fred Shaw Mayer in 1938.

3. Palila: This species of Hawaiian honeycreeper has one particularly mysterious characteristic—it subsists almost exclusively on the seeds of the māmane plant, which contain a level of toxins that would kill any other small animal. Scientists aren’t sure how the birds digest the seemingly-lethal seeds, although the palila have been observed avoiding certain plants, indicating they might have a way of selecting seeds with lower levels of poison. In 1978, the federal government ruled that feral goats and sheep had to be removed from the palila’s only remaining habitat—the upper slopes of Mauna Kea on the Big Island of Hawai’i—since they consumed māmane plants and threatened the birds’ survival.

The flightless kakapo nearly went extinct when invasive predators were intentionally introduced to New Zealand. Image via Wikimedia Commons/Brent Barrett

4. The Kakapo: Some 82 million years ago, the island of New Zealand broke off from what would become Australia, and the strange, flightless nocturnal parrot species called the kakapo began its unusual evolutionary path. In the absence of predators, it became the world’s largest type of parrot and lost the ability to fly; when European colonists introduced cats, rats and ferrets to New Zealand to control the population of rabbits, the kakapo was nearly wiped out. Now, just 126 wild kakapos live on three predator-free islands off the coast of New Zealand.

5. The Crested Ibis: Named for the crest of white plumage that extends from its nape, the crested ibis used to nest across Japan, China, Korea, Taiwan and Russia. By 1981, after years of habitat loss, just five individuals remained in the wild in Japan, and though scientists took the birds into captivity, a breeding program was unsuccessful. Now, the last remaining wild population—some 500 birds in the Chinese province of Shaanxi—is being buttressed by chicks hatched in captivity as part of a Chinese program. Although the species is still listed as endangered, scientists are cautiously optimistic that it is finally making a comeback.

An Air Force plane sprays dispersant onto the Gulf of Mexico following the Deepwater Horizon spill. New research could produce safer dispersants that include ingredients found in food. Photo via Wikimedia Commons/Adrian Cadiz

Two years ago, the explosion and subsequent oil spill from the Deepwater Horizon well in the Gulf of Mexico put oil dispersants in the news. In order to protect the Gulf coastline and minimize damage to oceanic ecosystems, dispersant chemicals were sprayed at the source of the leak—as well as on the floating sheet of oil on the water’s surface—to break up and dilute the harmful substance.

Many questioned the safety of the dispersants, however, and several of the ingredients in the chemicals deployed were shown to be toxic. Additionally, some scientists have argued that spreading oil throughout the water column, instead of leaving it concentrated on the surface, does more harm than good.

“The use of a traditional dispersant really comes down to the lesser of two evils,” says Lisa Kemp, a University of Southern Mississippi researcher who works on developing next-generation oil dispersant technologies. “Even if you have the safest possible dispersant, the components of the oil are toxic. So do you leave the oil on the surface of the water, where birds and other aquatic animals can be exposed to it, or do you add this dispersant to break the oil into small drops and send it through the water?”

Someday soon, though, oil spill cleanup coordinators might not have to make this type of difficult decision. Research by Kemp and her colleagues is yielding dispersants that are entirely harmless—and, intriguingly, are actually made from ingredients found in some familiar foods. ”Each of the ingredients in our dispersant is used in common food products like peanut butter, chocolate and whipped cream,” says Kemp, describing research she is presenting today at the American Chemical Society national meeting in Philadelphia. ”Other scientists are working on new oil dispersants and absorbents but nothing that’s quite like ours.”

Her research team’s new dispersant has another huge advantage over traditional dispersants: It’s extremely buoyant. The conventional approach is to break up an oil slick into tiny droplets that sink underneath the surface, so they improve the cosmetic appearance of the spill, but that puts new portions of the local ecosystem at risk. The new type of dispersant breaks up the slick into droplets that stay afloat, so they are made more available for oceanic microbes to digest and can also be more easily cleaned up by mechanical means such as boats with skimmers and absorbent booms.

A bird covered in oil in the aftermath of a spill. The new dispersant could prevent oil from sticking to birds and other wildlife. Image via Wikimedia Commons/Marine Photobank

Additionally, the new dispersant includes special non-stick polymers, so it is more effective than conventional formulas at protecting wildlife in the event of a spill. “It not only breaks up oil but prevents the deposition of oil on birds and other objects,” she explains. “Birds can sit in slicks of the dispersed oil, they can dive through it and take off and flap their wings, and the oil will fall off.”

Normally, removing oil from birds after a spill requires the use of detergents, which can remove their feathers’ natural waterproof coating. This leaves them less buoyant and more at risk of contracting hypothermia. Left to their own devices, birds often try to eat the oil on their feathers, leading to internal damage. The fact that the new dispersant prevents oil from sticking could be a huge boon for seabirds.

In order to develop the innovative dispersant, Kemp and her colleague, Robert Lochhead, looked to decades-old concepts from an unlikely source: the laundry detergent industry. Their polymer that coats the oil droplets and prevents them from sticking to birds, for instance, is inspired by a common ingredient in laundry detergent that prevents oil removed from a piece of clothing from getting re-depositing on other items in the wash. “Detergents include anti-redeposition agents that stick to oil and grease droplets removed by washing and keep them suspended in the water,” Kemp says.

After successfully testing their dispersant in the lab, Kemp and her team are looking to proceed to field trials of the substance on a larger scale. Although no one wants to see another maritime significant maritime oil spill, if the new dispersant proves successful, we may at least have a safer option for cleaning it up.

A new study reveals that the African grey parrot is capable of abstract reasoning. Photo via Wikimedia Commons/Yooth

When we think about the smartest animals, chimpanzees are usually the first to come to mind. Experiments show that they can memorize sequences of numbers, learn the meaning of words and associate particular voices with specific faces. Crucially, previous studies have found that chimps and other apes are the only non-human animals capable of making abstract logical inferences based on cues from their environment.

A new experiment, though, might make us recognize that an entirely different species belongs in this exclusive group: the African grey parrot.

In several previous experiments, researchers claimed they’d revealed the ability of parrots to make inferences based on their skill in completing an extremely simple task. The animals were shown a pair of closed canisters, one with food inside and one empty, and the top of the empty one was briefly opened. Afterward, when they were given the chance to choose one or the other, they reliably selected the one with food. Critics, though, said that this didn’t necessarily demonstrate any sort of inferential reasoning—they could simply be avoiding the empty canister, rather than realizing its emptiness implied there was food in the other.

A parrot selects between canisters as part of the study. Image via LiveScience/Arbeitsgemeinschaft Papageienschutz

In the new study, however, published yesterday in the Proceedings of the Royal Society B, researchers from the University of Vienna gave six grey parrots a slightly more complex task. Instead of being shown an empty and a full canister, the researchers merely shook one of the containers, so the parrots could hear either the sound of walnuts rattling around inside or silence.

When given the chance to select a canister, the parrots consistently chose the one with the walnuts, whether they had heard the shaking of either container. They were able, therefore, to determine both that a noisy shaking meant “food is inside” and that a noiseless shaking meant “no food is inside, so it must be in the other one.”

To confirm that the parrots were actually making inferences about the location of food, and not merely avoiding a silent box, the researchers introduced one more variation to the task. Instead of using the actual canisters to make the noises, they wore small speakers on their wrists that emitted shaking noises. In some cases, they shook the box in their right hand, but emitted the shaking noises from a speaker on their left wrist; in other cases, they played the sounds from the correct side. The parrots only made the right selection on a consistent basis when the sound lined up with the shaking—so they were making an inference not based on a visual or aural cue alone, but from noting the connection between both.

Although this might not seem that impressive, no other non-primate species has been able to successfully complete this type of task, and humans are not typically able to do this until they reach three years of age. The fact that the parrots were able to make these sorts of judgements based on sounds associated with food—and visuals that would logically produce the sounds—confirms that they are indeed capable of abstract, inferential reasoning. ”It suggests that grey parrots have some understanding of causality and that they can use this to reason about the world,” lead author Christian Schloegl told LiveScience.

Most interesting, from an evolutionary perspective, is the fact that parrots are not close relatives of primates, so their ability to reason presumably evolved separately. ”The most important point is that higher intelligence is nothing that evolved only once,” Schloegl said. “Comparable cognitive skills evolved several times in parallel in only distantly related species such as primates and birds.”

Fireworks can startle birds so badly they become disoriented (courtesy of flickr user SJ Photography)

On January 1st of this year, we awoke to reports of thousands of birds dead in Arkansas. The cause was not immediately known, and some people started to freak out, even saying that the event was a sign of the coming apocalypse.

Of course, within days scientists had an answer–the birds were likely startled by fireworks and, unable to see in the night, they ran into houses and signs and other objects and died from the trauma.

It turns out that birds are easily startled by fireworks. A study in the November/December issue of Behavioral Ecology used weather radar to track birds disturbed by New Year’s Eve fireworks for three years in the Netherlands. They found that thousands of birds took to the skies shortly after midnight and didn’t settle down again until 45 minutes later.

The scientists estimated that hundreds of thousands of birds, including several species of migratory waterfowl, were disturbed by the fireworks each year in the Netherlands alone. “The unexpected loud noises and bright lights fireworks produce are probably a source of disturbance for many species of domestic and wild animals,” the scientists wrote.

Most of the time, birds won’t die from the fireworks displays, as they did in Arkansas, the researchers note. But they still suffer from disrupted sleep, interrupted feeding and the energetic costs of flight and resettlement.

So, if you wake up on Sunday morning to more reports of dead birds, don’t think it’s Armageddon, but have a thought for the effects of our pretty displays on the wildlife around us.

There are 200 million European starlings in North America (courtesy of flickr user goingslo)

If you live in North America, you probably recognize European starlings, those little black birds with white polka dots that chirp and chatter and, in the winter, hang out in flocks of thousands. There are 200 million of these birds on the continent, and they can be found as far north as Alaska and as far south as Mexico. Numerous though they are, starlings are actually non-native invasive species. And we can blame Shakespeare for their arrival in America.

Steven Marche explains in How Shakespeare Changed Everything:

On March 6, 1890, a New York pharmaceutical manufacturer name Eugene Schieffelin brought natural disaster into the heart of [New York City] completely without meaning to. Through the morning snow, which congealed at times to sleet, sixty starlings, imported at great expense from Europe, accompanied Schieffelin on the ride from his country house into Central Park—the noisy, dirty fulfillment of his plan to introduce every bird mentioned by Shakespeare into North America. Schieffelin loved Shakespeare and he loved birds….The American Acclimatization Society, to which he belonged, had released other avian species found in Shakespeare—the nightingales and skylarks more commonly mentioned in his plays and poems—but none had survived. There was no reason to believe that starlings would fare any better. Schieffelin opened the cages and released the birds into the new world, without the smallest notion of what he was unleashing.

For someone who apparently loved birds, you have to admit this was a pretty daft plan. There was every reason to believe that the birds would die—it was bitterly cold and sleeting, and attempts with other species had led to dead birds. But the tiny flock found shelter beneath the eaves of the American Museum of Natural History, just to the west of the park, and they survived the winter. And then they began to breed, and spread, and breed some more.

It seems that the starlings some special characteristics that gave them an advantage over other bird species, Marche writes:

The protractor muscles of their beaks allow them to pry and to probe better than other birds. They can open their bills after pushing them into the soil, which allows them to forage for invertebrates easily and in drier areas. The starling’s eye have evolved to the narrow front of its face, giving it the perfect view for prying. Its binocular vision combined with its open-bill probing ability means that starlings can find insects in colder climates better than other birds, which means that starlings do not have to migrate to warmer climates in winter, which means that they can take the best nesting holes during the breeding season.

Starlings will bully other birds, kicking bluebirds, flickers and woodpeckers out of their nests. They can consume whole fields of wheat and transmit avian, animal and human diseases. A fungus called Histoplasma capsulatum can grow in the soil beneath roosting starlings; the fungal spores can become airborne if the soil is disturbed and cause the disease histoplasmosis, which, in rare cases, can cause blindness or death.

People quickly realized what a pest these birds could be and tried to get rid of them. In Hartford, Connecticut, in 1914, residents tried to scare the birds away from their nests by fastening teddy bears to those trees and firing rockets through the branches. The White House tried speakers that emitted owl calls. Columns around the U.S. Capitol were outfitted with electrified wires. People have tried shooting, poisoning, trapping, repelling and frightening the birds, but the population still grows. They have plenty to eat and lots of habitat to live on—what else does a species need?

These birds are a prime example of why it can be so difficult to control an invasive species once it has become established—no matter how many you wipe out, there’s still plenty to take their place.

Captive zebra finches (courtesy of flickr user psmithson)

I’m sure this pains the people who take offense at the true-life tale And Tango Makes Three, but heterosexuality is not the rule in the animal world. There are hundreds of species, from bison to bunnies to beetles, that pair off in same-sex couples. (And then there are bonobos.) Birds often pair off this way, too. And now a study of zebra finches, published in Behavioural Ecology and Sociobiology, has found that the bonds between same-sex couples can be just as strong as those in heterosexual birds.

Zebra finches, which live in grasslands and forests of Australia and Indonesia, form pairs that last a lifetime. The males sing to their partners, and the two share a nest and clean each other’s feathers. They nestle together and greet each other by nuzzling beaks.

Researchers raised groups of zebra finches in same-sex groups, all male and all female, and in each group the majority of birds paired up. They interacted frequently and often preened their partners. And they weren’t aggressive to each other as they were to other birds in the group. These are all characteristics found in heterosexual finch couples.

The scientists then tested the bonds in the male-male couples by introducing some females to the party. A few birds were tempted by the ladies, but when the females were removed, the male-male couples reformed.

“A pair-bond in socially monogamous species represents a cooperative partnership that may give advantages for survival,” lead author Julie Elie, of the University of California Berkeley, told BBC News. “Finding a social partner, whatever its sex, could be a priority.” Having a mate could help a bird to find food or repel predators.

Elie also told BBC News, “relationships in animals can be more complicated than just a male and a female who meet and reproduce, even in birds.” Or in humans.