Unexpected Look of the Ears of Crows

It’s nice to see this happy crow.

The footage below, posted by trained crow handler and animal volunteer Olly Peckar, shows a very happy crow getting some gentle pets while Olly exposes its ear from underneath its feathers.

Let’s just say we weren’t expecting something that… big?

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Avian ears lack the external pinnae that our human ears have, but they do have an internal cochlea like us – only it’s not shaped like a spiral, it’s mostly straight.

Birds are known for their keen sense of hearing, and also their ability to figure out if a sound is coming from above, below, behind, or next to them.

Wherever the source is situated, somehow a bird is able to localise it, and all without an external ear structure like mammals have.

Scientists have only recently figured out how they do this, and it turns out that in lieu of an external ear, birds use their entire heads to detect the location of incoming sound waves.

“Because birds have no external ears, it has long been believed that they are unable to differentiate between sounds coming from different elevations,” Hans A. Schnyder from the Technische Universität München in Germany explained.

“But a female blackbird should be able to locate her chosen mate even if the source of the serenade is above her.”

Back in 2014, Schnyder and his team investigated the hearing ability of three bird species – crow, duck, and chicken.

They found that the birds were able to identify sounds from different elevation angles thanks to their slightly oval-shaped heads, which appear to process sound waves in a similar way to the external ears of mammals.

Turns out, birds receive different sounds at different volumes, and this helps them figure out the general direction of the source.

Sounds originating from the same side as the ear hit the eardrum at a certain frequency, but once they passed through the head and reached the eardrum on the other side, they would register at a different frequency.

“The eardrum differences allowed the bird’s brain to determine whether the sound was coming from above or below or at level with the bird,” CBC News explains. “That meant the bird’s head was able to reflect, absorb or diffract the sounds.”

Research Into Crows Making Tools

Why surprisingly intelligent crows make elaborately crafted tools — increased efficiency at catching food.

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The new study, published in Nature Ecology & Evolution today (22 January), explores why crows go the extra mile rather than using simple, unmodified sticks to extract prey — it allows them to get at hidden food several times faster than if they used basic (non-hooked) tools.

[…]

Biologists have long assumed that there was some benefit to crows manufacturing hooked tools, but had no idea just how much better they might be. The Scottish team conducted experiments to record how long wild-caught crows took to extract food from a range of naturalistic tasks, using either hooked or non-hooked tool designs.

Depending on the task, they found that hooked tools were between two and ten times more efficient than non-hooked tools. “That’s a huge difference!” says project leader, Professor Christian Rutz from the University of St Andrews. “Our results highlight that even relatively small changes to tool designs can significantly boost foraging performance.”

These new findings help explain why New Caledonian crows have evolved such remarkable tool-making abilities: “In nature, getting food quickly means that birds have more time and energy for reproduction and steering clear of predators. It’s really exciting that we were able to measure the benefits of these nifty crow tools,” adds study co-author Professor Nick Colegrave from the University of Edinburgh’s School of Biological Sciences.

Scientists still don’t know how crows acquire the ‘know-how’ and make hooks; they may inherit the ability from their parents, or learn by observing experienced birds. Either way, because hooked-tool users will live longer and leave more offspring, the skill is expected to spread.

Professor Rutz notes wryly: “We’ve all heard that the early bird gets the worm. In the case of the New Caledonian crow, it’s the skilled hook-maker that gets the worm, or at least it gets many more worms than its less-crafty neighbours!”

Wonderful Facts About Ravens and Crows

This article has a nice compilation on the wonders of corvids. Additional h/t to https://corvidresearch.blog — the corvid research shown there has been valuable.

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We’re sure you have your favourite animal. It may even be a really smart one. But corvids – such as crows, magpies and ravens – really are something special. In fact, they’re some of the most intelligent animals in the world.

And here we’ve gathered some of the finest examples of just how clever these gorgeous creatures can be.

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In an experiment with tubes published in PLOS One, scientists determined that New Caledonian crows can not only tell the difference between water and sand – they also understand water displacement.

The test involved tubes containing water and a treat floating on top out of reach. The crows filled the tubes with enough rocks or other heavy items to bring the food within reach.

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Ever wonder why crow researchers sometimes wear masks? It’s because crows can recognise human faces, especially the faces of humans who have done them wrong.

So, if you’re trying to record how crows react to negative stimuli (such as being caught and tagged), you don’t want to do that using your real face. If you do, you’ll get loudly scolded by the agitated flock every time you approach, as biologist John Marzluff discovered and detailed in a 2011 paper.

Good thing he did, too. A few years later, he found out that crows not only hold onto that grudge – they tell other crows about it, too.

Within the first two weeks after trapping, around 26 percent of crows scolded the human wearing the danger mask. Around 15 months later, that figure was 30.4 percent.

Three years after the initial trapping event, with no action towards the crows since, the number of scolding crows had grown to 66 percent.

[…]

When a crow dies, other crows are often observed gathering around and making a lot of loud noise – much like humans, really. The reason for this was unknown until 2015, when crow researcher Kaeli Swift crowdfunded research to try and figure out why.

Her conclusion, published in the journal Animal Behaviour, was that crows gather around their dead fellows to learn about danger.

And it works. The city of Chatham, Ontario is beneath a crow migration route, and they plague the town on their way through. Every attempt to get rid of them has failed – including shooting at them with pellet guns. The crows learnt how to fly just high enough to evade the fire.

[…]

6. Crows can solve complex, multi-step puzzles

This crazy impressive experiment was conducted as part of a BBC Two program called Inside the Animal Mind, putting crows to the test with the most complex animal puzzle ever.

And not lab crows, either. The crows were captured from the wild one at a time, and kept for just three months.

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In 2015, researchers announced they had filmed the first ever video evidence of crows fashioning tools in the wild using a specially developed spy camera mounted on the crows’ tail feathers.

They were observed snapping twigs from trees, then stripping it of bark and leaves, and fashioned the node into a hook. They then used these tools to probe into small spaces for food.

“The behaviour is easy to miss – the first time I watched the footage, I didn’t see anything particularly interesting. Only when I went through it again frame-by-frame, I discovered this fascinating behaviour. Not once, but twice!” researcher Jolyon Troscianko said.

“In one scene, a crow drops its tool, and then recovers it from the ground shortly afterwards, suggesting they value their tools and don’t simply discard them after a single use.”

[…]

In a 2015 study, researchers from the University of Vienna gave ravens a task wherein they would only receive the reward if they cooperated, pulling on ropes to raise a platform which had two pieces of cheese, one for each raven.

If one raven stole their companion’s cheese, as well as their own, they were on the outs: the other raven would refuse to cooperate with them – but they would cooperate with other ravens who played fair.

“Such a sophisticated way of keeping your partner in check has previously only been shown in humans and chimpanzees, and is a complete novelty among birds,” lead researcher Jorg Massen said.

[…]

9. Crows can exercise self control

Crows aren’t driven purely by instinct – they can experience anticipation, and exercise self-control if the end result is a greater reward.

2014 study devised a test based on the Stanford marshmallow experiment, a 1960s study into delayed gratification in children. The first step was to determine which snacks the crows liked the most. The researchers fed them grapes, bread, sausage, fried fat and other treats.

Next, they were given a snack and the option to trade their snack – if they were willing to wait. They could either receive a better quality snack – meat in exchange for a grape, for instance – or a higher quantity of the same snack.

The birds preferred to wait until a better snack was on offer, but if it was just more of the same, they weren’t. In some cases, they waited up to 10 minutes for a better snack. The fact that they waited for better quality, not quantity, showed that they were waiting because they wanted to – not because they were actually hungry.

[…]

11. Ravens remember people who have been nice to them

You know how crows hold a grudge? Well, corvids also remember people who have been nice to them. There was, of course, that adorable case of a little girl who crows started bringing shiny objects to after she regularly fed them – but there’s been a scientific study on the subject too.

Again, it involves ravens trading a low-quality snack (bread) for a high-quality snack (cheese), which they’d been trained to do. Then two humans brought the cheese to trade for the bread. One experimenter would fairly give the cheese when the crow handed over the bread. The other experimenter ate the cheese themselves after being given the bread.

Then, after an interval – two days, and then later one month – three humans entered the enclosure, the fair one, the unfair one, and a neutral control. The raven was given a piece of bread to trade. Most of the ravens chose to trade with the fair experimenter – indicating that they remembered being cheated out of delicious cheese and weren’t falling for that again.

Study Reveals the Wonderful Depth of Intelligence Crows Have for Creating Tools

Crows are surprisingly intelligent and amazing creatures.

New Caledonian crows are the only species besides humans known to manufacture hooked tools in the wild. Birds produce these remarkable tools from the side branches of certain plants, carefully ‘crafting’ a crochet-like hook that can be used for snagging insect prey.

The study, published in Current Biology today (7 December), reveals how crows manage to fashion particularly efficient tools, with well-defined ‘deep’ hooks.

The hook is widely regarded as one of humankind’s most important innovations, with skilful reshaping, a useless piece of raw material is transformed into a powerful tool. While our ancestors started making stone tools over 3 million years ago, hooks are a surprisingly recent advance — the oldest known fish hooks are just 23,000 years old.

Project leader Professor Christian Rutz, from the School of Biology, has conducted field research on New Caledonian crows for over a decade. His team recently noticed that crows’ hooked tools vary considerably in size and shape. While some tools only exhibit a small extension at the tip, others have immaculate hooks.

Professor Rutz explains: “We suspected that tools with pronounced hooks are more efficient, and were able to confirm this in controlled experiments with wild-caught crows. The deeper the hook, the faster birds winkled bait from holes in wooden logs.”

This finding raised the intriguing question of what it takes to make such well-formed hooks. The researchers started planning their study by imagining how humans would approach a comparable task. “When a craftsperson carves a tool from a piece of wood, two things ensure a quality product: good raw materials and skill,” Professor Rutz said.

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