Curious Kids: how do magpies detect worms and other food underground?

Magpies have a few clever tricks to help them find food.
Gisela Kaplan, Author provided

Gisela Kaplan, University of New England

How do magpies detect worms and other food sources underground? I often see them look or listen, then rapidly hop across the ground and start digging with their beak and extract a worm or bug from the earth – Catherine, age 10, Perth.

You have posed a very good question.

Foraging for food can involve sight, hearing and even smell. In almost all cases learning is involved. Magpies are ground foragers, setting one foot before the other looking for food while walking, called walk-foraging. It looks like this:

This is called walk-foraging.
Gisela Kaplan, Author provided

Finding food on the ground, such as beetles and other insects, is not as easy as it may sound. The ground can be uneven and covered with leaves, grasses and rocks. Insects may be hiding, camouflaged, or staying so still it is hard for a magpie to notice them.

Detecting a small object on the ground requires keen vision and experience, to discriminate between the parts that are important and those that are not.

Magpie eyes, as for most birds, are on the side of the head (humans and other birds of prey, by contrast, have eyes that face forward).

A magpie’s eyes are at the side of its head and it can only see something with both eyes if that is straight in front of the bird.
Shutterstock/Webb Photography

To see a small area in front of them, close to the ground, birds use both eyes together (scientists call this binocular vision). But birds mostly see via the eyes looking out to the side (which is called monocular vision).

This picture gives you an idea of what a magpie can see with its left eye, what it can see with its right eye and what area it can see with both eyes working together (binocular vision).

Here’s how a magpie’s field of vision works.
Gisela Kaplan, Author provided

You asked about underground foraging. Some of that foraging can also be done by sight. Worms, for instance, may leave a small mound (called a cast) on the surface and, to the experienced bird, this indicates that a worm is just below.

Magpies can also go a huge step further. They can identify big scarab larvae underground without any visual help at all.

Here is a scarab larva.
Gisela Kaplan, Author provided

Scarab larvae look like grubs. They munch on grassroots and can kill entire grazing fields. Once they transform into beetles (commonly called Christmas beetles) they can do even more damage by eating all the leaves off eucalyptus trees.

Here is the secret: magpies have such good hearing, they can hear the very faint sound of grass roots being chewed.

We know this from experiments using small speakers under the soil playing back recorded sounds of scarab beetle larvae. Magpies located the speaker every time and dug it up.

An Australian magpie digging for food in a lawn.
Flickr/Lance, CC BY-NC-ND

So how do they do it? Several movements are involved.

To make certain that a jab with its beak will hit the exact spot where the juicy grub is, the magpie first walks slowly and scans the ground. It then stops and looks closely at the ground – seemingly with both eyes working together.

Then, holding absolutely still, the magpie turns its head so the left side of the head and ear is close to the ground for a final confirming listen.

Finally, the bird straightens up, then executes a powerful jab into the ground before retrieving the grub.

An Australian magpie digging for food gets a grub.
Wikimedia/Toby Hudson, CC BY-SA

That is very clever of the magpies. Very few animals can extract food they can’t see. Only great apes and humans were thought to have this ability. Clever magpies indeed. And farmers love them for keeping a major pest under control.

Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to curiouskids@theconversation.edu.au

Gisela Kaplan, Emeritus Professor in Animal Behaviour, University of New England

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Cable ties probably won’t stop magpie attacks – here are a few things to try instead

Stylish? No. Effective? Probably not.
Tony Wills/Wikimedia Commons, CC BY

Bill Bateman, Curtin University

Every spring in Australia is heralded by reports of magpies swooping at people. While it is of little comfort to those at the receiving end of a surprise attack, such events are actually quite rare when one considers the number of magpies across Australia, and the fact that they love to share our urban habitat with us.

According to one estimate, fewer than 10% of magpies swoop, and even fewer of these do so consistently. It is almost always males that swoop, and they only do so when they have chicks in the nest. Once the chicks are out the males seem to calm down; presumably they perceive nest-bound chicks as most vulnerable.

Swooping behaviour also seems to vary across Australia – at least according to Magpie Alert!, a website on which the public can report magpie attacks. Many more swoops have been reported in the eastern states than in Western Australia, and fewest of all in Tasmania.

But regardless of their relative rarity, being the target of a swooping attack by a magpie can be frightening. It has resulted in injuries and, tragically this week, the death of a 76-year-old cyclist in Wollongong.

What can we do to avoid ending up on the receiving end? Is any of the advice meted out each year on avoiding attacks actually worthwhile, or backed by evidence? As with just about everything involving biology, the answer is “it depends”.

Some magpies never attack pedestrians but go for cyclists; others do the opposite. And some hold a deep animus against posties on bikes, and reserve their fury solely for them. Even more astonishingly, some magpies seem to really have it in for particular people, and will preferentially attack them.

Although Australian magpies are not related to true crows, they do share similar levels of intelligence. US researchers have shown that American crows recognise people who have trapped them to band them, give alarm calls when they next see them, and even pass on that information to untrapped birds who also sound the alarm when they see trappers.

It seems likely that Australian magpies do the same, effectively holding a grudge against particular people. Unfortunate posties, travelling the same route each day and meeting the same magpies, seem to end up on the naughty list through no fault of their own.

Cyclists do seem to invoke more extreme reactions than pedestrians, judging by the fact that magpies appear to pursue cyclists farther. It therefore stands to reason that the best response to a swooping attack while cycling would be to get off and push your bike.

You will of course be wearing a bike helmet, and as magpies swoop from behind, this will offer protection against its sharp beak.

Sadly it seems that the classic tactic of attaching cable ties to your helmet does little to deter a determined magpie, beyond the fact that some strategic placing can help keep them away from your ears. Ditto the idea of painting eyes on the back of your helmet or hat.

More reassuringly, however, magpies really only swoop in the vicinity of their nest, so once you have moved away you should be safe. If you become aware of swooping attacks in a certain area the best thing is to avoid it – even just crossing the road should be sufficient.

If you can’t do that, at least wear a hat and sunglasses; these will help reduce the chance of a determined magpie pecking a sensitive area. Turning to face magpies may also help – many birds do not appreciate being stared at, and as magpies prefer to swoop from behind, this may be a good tactic if you find yourself cornered in a park.

If you have magpies in your garden, perhaps the most appealing way of avoiding attacks is to become their best friend. Given that magpies have long memories, a few judicious offerings of mince or similar tidbits throughout the year can help you befriend them, making them much more amenable to your presence come spring.

But don’t overfeed them – it’s just a friendly bribe, not a full-blown dependency.

If all else fails, simply console yourself with the fact that swooping season only lasts a few weeks. For the rest of the year magpies are peaceful urban nighbours who delight us with their distinctive song.

Bear that in mind, and we can hopefully reach a détente with our feathered (and occasionally flustered) friends. In the meantime, if you are unlucky enough to be swooped, remember to help others avoid the same fate by posting the details to Magpie Alert!.

Bill Bateman, Associate professor, Curtin University

This article is republished from The Conversation under a Creative Commons license. Read the original article.