Long Before Europeans, Pacific Island Birds Went The Way Of the Dodo

574px-Chelychelychen_quassusThe extinction of the dodo is so well known, it became an idiom. But to recap: The large flightless bird was discovered on Mauritius in 1598 as the Dutch were settling the Indian Ocean island. By 1662, the bird was extinct, wiped out by humans and the animals they brought with them who found the dodo tasty and easy to catch.

It might be easy to think that such a phenomenon is a modern one, that as Europeans branched out and settled the world, they brought death and destruction to the lands they conquered. But it wasn’t just Europeans, as a study published today by PNAS shows.

The goal of the study, led by the University of Canberra in Australia, was to estimate the number of bird species that went extinct as humans colonized remote islands in the South Pacific. These islands were some of the last places in the world to become inhabited — ranging from New Caledonia and Fiji, settled some 3,500 years ago, to Hawaii, around 700 to 900 years ago. And as with the dodo, when humans arrived, birds disappeared.

Determining how many bird species the islands once had, though, is rather difficult. Fossils are scarce for a lot of the islands. And differences in islands and species make generalizations from one island to the next complicated. The researchers got around this by employing a common technique from ecological studies: mark and recapture. The species that were on an island when Europeans arrived were the “marked” individuals and the fossil species were those that were “recaptured.” With those numbers, the scientists could extrapolate how many species had once existed on an island. And from the 41 islands they studied, they could extrapolate further to the group of 269 remote Pacific islands.

The research focused on nonpasserine land birds, which are better documented in the fossil record. The researchers estimated that about 1,000 species of these birds went extinct after humans arrived on these islands but before Europeans showed up. That’s around two-thirds of the distinct species that once inhabited those islands.

Most vulnerable were, not surprisingly, flightless birds and larger species, those that would have made for the easiest and best meals.

And the fewer islands on which a species could be found, the more likely it was go extinct; those that were endemic to a single island were among the most likely to disappear.

Smaller islands and those with less rainfall were also more likely to see extinctions. “Islands with lower annual rainfall were more extensively deforested in the period between first human and European arrival,” the authors write, “suggesting that higher rates of extinction were associated with greater loss of forest habitat in lower-rainfall areas.”

New Zealand was not included in the study, but the researchers say that its “large size, rugged landscape, and high rainfall sets it apart” from other Pacific islands, with the result that some large flightless birds, like the kiwi, have managed to survive.

That humans have been driving species to extinction for a long time is not really a shocker, though. Hunting, habitat destruction, the introduction of invasive species — these are not modern inventions, and neither are their results.

Image of moa-nalo by Stanton F. Fink, via wikimedia commons

Swallows Evolve To Avoid Becoming Roadkill

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Evolution works pretty fast sometimes. Biologists Charles Brown of the University of Tulsa in Oklahoma and Mary Bomberger Brown of the University of Nebraska-Lincoln have found that over a period of just 30 years, the cliff swallows (Petrochelidon pyrrhonota) of southwestern Nebraska evolved shorter wingspans that help them avoid getting hit by cars. Their study appears in Current Biology.

The discovery is a byproduct of a long-term study of the social behavior of the swallows, which nest in colonies beneath horizontal overhangs. They attach their gourd-shaped mud nests to sites like highway bridges, overpasses, and the concrete beneath railroad tracks.

In the 30 years of their study, the researchers drove the same roads, year after year, to check on the birds, stopping to pick up dead swallows whenever they found them. But they found something intriguing: The swallow population as a whole increased over that time, but the number of birds that became roadkill fell. In addition, the birds that got hit by cars had longer wings, on average, than the population as a whole, and the difference in wing length became more pronounced over time.

Factors like weather, changes in the prey population, or learning could explain either the difference in wing length or the decline in roadkill, but not both. Instead, the researchers say that natural selection likely favors birds that have a wing morphology that allows them to escape ongoing vehicles.

“Longer wings have lower wing loading and do not allow as vertical a take-off as shorter, more rounded wings,” the researchers write. “Thus, individuals sitting on a road, as cliff swallows often do, who are able to fly upward more vertically may be better able to avoid or more effectively pivot away from an oncoming vehicle.”

Image credit: Current Biology, Brown et al.

Cockatoos Pass The Marshmallow Test, Sort Of

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In the classic marshmallow test, a treat is place before a child who is told if they don’t eat it and instead wait until an experimenter returns, they’ll get two treats. About a third of four-year olds can make it through the minutes that follow without eating the marshmallow. Some primates, dogs and corvids have also passed similar delayed gratification tests, but monkeys, rodents and most other birds — including the African grey parrot, famed for its intelligence — have failed.

The Goffin’s cockatoo has also shown signs of intelligence; like corvids, this bird has been found to be a capable toolmaker. So how’s its self control? Researchers from the University of Vienna gave it a test and publish their results this week in Biology Letters.

The setup was even more challenging than the marshmallow test: A bird was presented with a pecan nut, which it had to pick up and hold in its mouth. Then either more nuts or a better nut, like a cashew, were shown to the bird, just out of reach. If the bird held the pecan without eating it, it would be given the other treat.

“Imagine placing a cookie directly into a toddler’s mouth and telling him, he will only receive a piece of chocolate if the cookie is not nibbled for over a minute,” the study’s lead author Alice Auersperg said in a statement.

Most of the cockatoos put to the test could hold out for two or five seconds. Half made it to 40 seconds, and a few made it to 80 seconds. None lasted to 160 seconds, the greatest amount of time tested. The birds were more successful in holding out for the cashew than for more food.

This is the first time a parrot species (cockatoos are parrots) has managed to pass a test of delayed gratification. Toddlers have them beat for time, but perhaps someone should try stuffing the marshmallow into a kid’s mouth to see if they really could hold out longer than a bird.

Image copyright Dr. Alice Auersperg, courtesy of the Royal Society

Did A Kid Design This Bird?

What is this bird that looks like a child’s drawing come to life? It’s called a Wilson’s bird-of-paradise (Cicinnurus respublica), and it can only be found in the hill and lowland rainforests of a couple of Indonesian islands. The video above shows a male of the species; females are drab and brown. (They may lack the pretty colors, but the girls’ camouflage is probably a better outfit in the long run.)

There are 39 species of birds-of-paradise, including this one, and they are noted for their spectacular coloring, weird feathers and elaborate mating dances (the males are the show-offs, both in feathers and dance).

The video is part of the Cornell Lab of Ornithology’s Bird-of-Paradise Project. Ed Scholes and wildlife photojournalist Tim Laman have photographed all 39 species of birds-of-paradise, a feat that took them eight years. Now they’re going back to New Guinea, where most of the birds can be found, to film the males from the females point of view. It’s something that’s leading to interesting insights, such as that the ballerina bird‘s name doesn’t really fit. When the female looks on the male doing this particular dance, he no longer looks like a bird wearing a tutu but a big black blob with occasional flashes of color.

An Uncertain Future For Vultures

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It can be difficult to feel sorry for a creature that lives by eating the dead. But vultures fill an important ecological niche, and removing them from the landscape can cause a cascade of changes with devastating consequences, as India has learned in recent years.

Vultures started disappearing from India during the 1990s. The cause, scientists later learned, was the painkiller, diclofenac. The drug is used to treat cattle in India (and elsewhere), but it’s toxic to vultures. When cattle die, the vultures eat the carcasses, get sick and also die. Vultures in India are disappearing faster than the dodo.

You might think that without the vultures to eat the carcasses of the dead, the bodies would just decay. But instead they’ve become a food source for rats and, worse, packs of feral dogs. Feral dogs are a growing problem in India, where they have attacked and killed children, and spread rabies and distemper, threatening a host of other species.

Now Africa could be facing the same problem, and hopes that vultures could be saved through the creation of protected areas have been dashed by a study in PLOS One that found that the birds roam farther than anyone suspected.

“We found that young vultures travel much further than we ever imagined to find food, sometimes moving more than 220 kilometers a day. Individuals moved through up to five countries over a period of 200 days, emphasizing the need for conservation collaboration among countries to protect this species,” study co-author Stephen Willis of Durham University in England said in a press release.

The reason vultures fly so far is that there’s just not enough food for them in the protected areas. Vultures prefer to eat animals that have died naturally, rather than compete with lions and other predators for their kills. The best place for a vulture to find a meal, then, is a pasture far from other carnivores. Sadly, though, the vultures don’t know that those pastures can contain some of the most deadly foods. And until people stop treating their cattle with the problem painkiller, the vulture populations will continue to decline.

Image Credit: Dr. Stephen Willis/Durham University

Where Did The Pigeon Get That Weird Thing On Its Head?

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Visit most any city on Earth, and you’ll find flocks of pigeons. And as you stare at the birds as you sip a cup of coffee at a sidewalk cafe, you may be fascinated by their diversity: varying in color, from white to grey to black to brown. Even the common grey ones all look a little different.

But true pigeon variety is really found in the 350 or so fancy breeds that have been developed since the bird was first domesticated 5,000 years ago. (Above, clockwise from upper left: English trumpeter, Brunner pouter, fantail, Italian owl, Chinese owl, Pomeranian pouter.)

One of the traits that can make a pigeon look extraordinary is the presence of a head crest. This headgear itself can come in a variety of looks, but scientists who have sequenced the genome of Columba livia (that’s the common rock pigeon) have found that “crest” or “no crest” is determined by a single gene, called EphB2.

The trait first becomes apparent when the birds are juveniles, but the mutant gene has effects even earlier in life: When the pigeon embryo is still in the egg, the gene causes molecular changes that reverse the direction of growth of the feathers on the top of the head.

The study was published online last week by the journal Science.

Images courtesy of Mike Shapiro, Science magazine