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?

happy-crow

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.

Crow-new-1-800x523 - Copy

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!”