This is an updated version of an old piece, edited to include new information. Science progresses by adding new data to an ever-growing picture. Why should science writing be different?

Right from its entrance, Disneyland is designed to cast an illusion upon its visitors. The first area –  Main Street – seems to stretch for miles towards the towering castle in the distance. All of this relies on visual trickery. The castle’s upper bricks and the upper levels of Main Street’s buildings are much smaller than their ground-level counterparts, making everything seem taller. The buildings are also angled towards the castle, which makes Main Street seem longer, building the anticipation of guests.

These techniques are examples of forced perspective, a trick of the eye that makes objects seem bigger or smaller, further or closer than they actually are. These illusions were used by classical architects to make their buildings seem grander, by filmmakers to make humans look like hobbits, and by photographers to create amusing shots. But humans aren’t the only animals to use forced perspective. In the forests of Australia, the male great bowerbird uses the same effect to woo his mate.

Bowerbirds are relatives of crows and jays that live in Australian and New Guinea. There are 20 or so species. In most of them, the male attracts mates by building an intricate structure called a bower, which he decorates with specially chosen objects. Some species favour blue trinkets; others collect a  mishmash of flowers, fruits, insect shells and more. Surrounded by these knick-knacks, the artistic male performs an elaborate display. The females judge him on his skill as a performer, builder and decorator.

The great bowerbird’s taste for interior design seems quite Spartan compared to his relatives. He creates an avenue of sticks, around 60 centimetres long, leading up to a courtyard. The courts are decorated with gesso – a collection of gray and white objects including shells, bones and pebbles.

(more…)

---

“God save thee, ocean sunfish
From the fiends that plague thee thus
Why look’st thou so? With thy large shoals,
Thou fed the albatross.”

- Samuel Taylor Coleridge, sort of.

Albatrosses are superb long-distance fliers that can scour vast tracts of ocean in search of food. But sometimes, food comes to them. In July 2010, Tazuko Abe from Hokkaido University found albatrosses cleaning a school of ocean sunfish, basking at the surface of the western Pacific Ocean.

The ocean sunfish is a truly bizarre animal. It looks like someone cut the head off a much bigger fish and strapped fins to it. It’s the largest of the bony fish*. The biggest one ever found was 2.7 metres in length and weighed 2.3 tonnes. The youngsters, of course, are much smaller. The ones that Abe saw on his research cruise were just 40 centimetres long. There were at least 57 of them, each turned on its side so its broad flank faced the water surface.

The basking shoals were attending a sort of sunfish spa. The fish were infested with parasites. Pennella, a long scarlet relative of shrimp and crabs, was embedded headfirst in the flesh beneath their fins, busily sucking their blood. But not for long – black-footed and Laysan albatrosses were attracted to the shoal and picked the Pennella off their bodies. In some cases, the sunfish seems to be courting the birds, following them around and swimming sideways next to them.

Ocean sunfish live throughout the oceans but they often spend time at the surface before diving to the depths. Some scientists think that they’re absorbing heat from the sun, but it’s possible that they could also be looking for a spot of personal hygiene.

These fish can play host to at least 50 species of parasites, and they often have considerable numbers on their large bodies. Many ocean animals rely on cleaner fish or cleaner shrimp to rid them of parasites. It’s possible that albatrosses might fulfil the same role for ocean sunfish.

Of course, the association might have been a one-off. However, there are other reports of seabirds such as shearwaters and albatrosses flocking around schools of basking sunfish. This instance stands out only because Abe has photographic evidence that they were actually parasites. As he rightly points out, such events would be difficult to spot among the vastness of the open ocean.

* Fish have skeletons that are either made of cartilage, as in sharks and rays, or bone, as in all the others.

Reference: Abe, Sekiguchi, Onishi, Muramatsu & Kamito. 2011. Observations on a school of ocean sunfish and evidence for a symbiotic cleaning association with albatrosses. Marine Biology http://dx.doi.org/10.1007/s00227-011-1873-6

In flight, the hovering hummingbird is more like a insect than a bird. Most most birds only create lift when they flap downwards. But the hummingbird, by flipping its wing before it flaps upwards, can create lift in both directions. Insects do the same thing, but their wings have no bones inside them. How does the hummingbird fly like a fly despite having the bones of a bird?

Tyson Hedrick has found out, by filming hovering hummers with high-speed X-ray cameras. I’ve written about the results in my new piece for Nature News, so go there and read the full story (including details about how hummingbird muscles work at high gear). The meat of it is this:

By filming ruby-throated hummingbirds (Archilochus colubris) in flight, Hedrick showed that the birds invert their wings by twisting their wrists. “It looks like it’s affecting the whole wing because the bird’s skeleton is very compressed and its wrist isn’t very far from its shoulder,” says Hedrick.

In most birds, the wrist collapses on the upstroke to draw the wing towards the body as it is raised. Hummingbirds have adapted the same movements to rotate their wings instead. “The usual mechanism makes the upstroke aerodynamically invisible,” says Hedrick. “The hummingbirds’ mechanism makes the upstroke aerodynamically effective.”

The videos also showed that hummingbirds flap their wings by twisting the humerus (upper arm bone), rather than flapping it up and down from the shoulder like other birds. To understand the difference, Hedrick recommends trying to mimic a bird by flapping your arms. “You’re doing something not too different to what a seagull’s doing,” he says. To mimic a hummingbird, “hold your upper arm close to your body with your elbow on your hip, and flap your forearms back and forth”.

Go try it. You can look as stupid as I did when I was writing about the paper.

Photo by Joe Schneid

We now know that birds evolved from small, feathered dinosaurs. It’s easy to think that since birds are still around today, they must have come after their dinosaur* cousins, but that’s not true. In the Cretaceous period, dinosaurs were still around while their descendants flitted through the skies. And some dinosaurs made meals of their flighty relatives. Jingmai O’Connor from the Chinese Academy of Sciences has uncovered the remains of a small dinosaur called Microraptor that has the bones of small bird in its gut.

O’Connor analysed the fossil with Xing Xu, a Chinese scientist who has made a career from discovering beautiful feathered dinosaurs. Microraptor is one of his most important finds. This tiny animal, about the size of a pigeon, had four wings, with long feathers on both of its legs as well as its arms. It was, at the very least, a very competent glider, if not a true flier.

(more…)

Male and female marsh harriers should be easy to tell apart: the males have grey wing-tips and tails, while the females are mostly brown with distinctive creamy heads. The males also tend to be around 30 percent smaller. But looks can be deceptive. In western France, many of the “female” harriers are actually cross-dressing males that permanently wear the plumage of the opposite sex. Audrey Sternalski has found that this unusual costume allows them to lead more peaceful lives.

Forty percent of male marsh harriers don female costumes, and they start wearing them from their second year of life. Their feathers have the same colours, and they’re smaller in size. Only their irises give them away – they are pale, rather than the ochre-brown of females or the yellow-white of males.

To test the effect of these colours, Sternalski created model harriers and placed them in the territories of real ones. He found that males attacked the male decoys twice as often as either the female or female-like ones. So, by looking like females, male harriers become the beneficiaries of a “non-aggression pact”. They can get access to resources and mates without incurring the wrath of other males. Indeed, Sternalski found that typical males were forced to nest twice as far from another male as the female-like males did.

Sternalski also found that the female-like males almost never attacked male decoys. Instead, they were more likely to attack other females (or female-like males), just as true females are. Not only did they look like females, they behaved like them too.

This raises several questions – are the female-like males simply doing a superficial impersonation, or are they “female” at a deeper physiological level? To find answers, Sternalski now plans to study the genetic basis of the harrier’s female mimicry.

The marsh harrier is one of only two birds whose males permanently don the colours of females. The other – the ostentatious ruff – also uses its disguise to avoid aggressive assaults. They sneak into the territories of more dominant males and surreptitiously mate with the resident females. Such strategies are fairly common in the animal kingdom – they’re found in ants, wasps, fish, and more. In most cases, the deceptive males get some sneaky sex, or avoid attacks from rivals.

But that’s not necessarily the case. In 1985, scientists discovered that some male red-sided garter snakes release a female pheromone that attracts big clusters of up to 17 amorous suitors. By luring these males to him, the female mimic more easily mates with an actual female. The goal seems obvious: distract other males. But the same group later showed that the female-mimics might simply benefit by drawing heat from the writhing balls of other duped males.

Reference: Sternalski, Mougeot & Bretagnolle. 2011. Adaptive significance of permanent female mimicry in a bird of prey. Biology Letters http://dx.doi.org/10.1098/rsbl.2011.0914

More on mimicry:

• Orchid flowers fool flat-footed flies by faking fungus-infected foliage
• The bird that cries hawk: fork-tailed drongos rob meerkats with false alarms
• Cuckoos mimic hawks to fool small birds
• Butterflies scrounge off ants by mimicking the music of queens
• The mimic octopus (my first ever post)
• Spider mimics ant to eat spiders and avoid being eaten by spiders

In the mountainous forests of Ecuador, you might hear this fast, lilting song:

The melody sounds like it comes from a single bird, but it is actually sung by two: one male and one female. The couple alternates their syllables with almost unbelievable precision, each one placing its notes in the gaps left by its partner. The result is one of nature’s finest duets. And the singers are a pair of (rather drably named) plain-tailed wrens.

By studying the singing wrens, Eric Fortune from Johns Hopkins University has found that each bird has brain circuits that encode the entire song. Rather than focusing on just their own contribution, they process the whole melody. Their duet is conceived as a whole in both their brains, but emerges as two distinct parts, one from each beak.

(more…)

Many birds sing to woo females, but some hummingbirds go to great lengths to do so. They climb to between 5 and 40 metres before plummeting past perched females in death-defying dives. They pull up at the last minute, spread their tail feathers and produce a loud chirpy song. The song comes not from the birds’ mouths, but from their tails. The splayed tail feathers vibrate as air rushes past them, causing them to flutter.

Flutter sounds colloquial and innocuous, but it can be deadly. It’s what happens when air, moving at just the right speed, zooms past objects with just the right stiffness, setting up large and potentially disastrous vibrations. Flutter brought down the passenger plane Braniff Airways Flight 542, killing everyone on board. Flutter wrecked the Tahoma Narrows Bridge, causing it to warp and twist like a piece of rope. But flutter also ensures that male hummingbirds get some action.

(more…)

---

One by one, three bee-eater chicks hatch in their underground nest, and they are all about to die. There is a fourth chick in with them, but it is no bee-eater. It is a greater honeyguide, a different species that was laid in the nest and mistakenly incubated by the bee-eater parents. Having hatched a few days ago, it has been lying in wait for its foster siblings. As each emerges in turn, the honeyguide attacks it with vicious spikes on its bill. Completely blind, it is literally stabbing in the dark but it makes up for its imprecision with brutality. Within minutes of entering the world, the other chicks are dead.

Warning: this video is not pleasant. Watch at your own risk.

(more…)

How does an ostrich sleep? Almost imperceptibly, it seems. Even though an ostrich might be sound asleep, it can look wide awake or, at most, a little drowsy. John Lesku from the Max Planck Institute of Ornithology discovered this by fitting six ostrichers with “Neurologgers”, electrode-laden helmets that measures their temperature, brain activity, eye movements and neck muscle contractions.

The video above shows three of the birds cycling through two different types of sleep. The first is called ‘slow wave sleep’ or SWS, where the ostriches’ brain waves are slow and strong. Even though this is typically known as deep sleep, the birds look alert. They stay still, but their eyes are open and their necks upright. Nonetheless, the readings from the Neurologgers clearly showed that they were asleep.

In the second phase, known as ‘rapid eye movement’ or REM sleep, the ostriches’ brain waves are fast and weaker. Now, the birds shut their eyes, which move rapidly behind closed eyelids. They necks also start to droop and sway, righting themselves with awkward jerks like people falling asleep at a talk. Biologists have previously interpreted this as a sign of a tired ostrich. That’s partly right, although the animal is already asleep rather than on its way.

(more…)

A stressful early life can have long-lasting consequences, not just for you but for your partner. Pat Monaghan from the University of Glasgow found that zebra finches are more sensitive to stress as adults if they had unusually high levels of stress hormones as chicks. To no one’s surprise, they also died at a younger age. But it came as more of a shock that these tightly wound finches passed the consequences of their early hardships to their partners. They too died earlier even if their early days had been stress-free.

A wide variety of animals react to stressful conditions by become physiologically more jumpy. Their bodies flood with stress hormones at slight provocations, and they take longer to return to normal. In the short term, these changes help animals to survive through difficult times. But they can also be harmful in the long term. Not only can they shorten an individual’s life, but they can turn it into an undesirable partner.

Many studies have found that individuals across many different species are less likely to secure mates when they grow up if they have stressful upbringings. This might be because they are less physically attractive but, based on his study, Monaghan thinks that it could also be that such individuals pose a health hazard to their mates.

(more…)