View From The Shed by Shaun Finnie - SENSES WORKING OVERTIME (PART 2)

SENSES WORKING OVERTIME (Part Two)

Last week I started looking at how the average birds' senses compared to a humans'. I covered sight, hearing and touch in the last View From the Shed (available to read here if you somehow missed it – where were you?) so it makes sense that this week I examine a bird's other senses and how we can relate them to our own. Sensibly. If you're ready, let's get straight into it, shall we?

Smell

For many birds the sense of smell is simply not much of a requirement. They do have one but it's nowhere near as well developed as our own. True, some birds use smell to locate their prey but these are mostly carrion feeders such as vultures, kites and some gulls. Most of the birds on the British list don't need to smell much of anything as they go about their daily lives.

You and I have about five million sensor receptors in our nose. A dog has between two- and three-hundred million receptors. That means that your pet pooch can smell things 40- to 60-times better than you can. But a common-or-garden songbird? No. It can detect far fewer smells than the average person.

But it's a little more complicated than that and even the best scientists are struggling to explain things fully. With that in mind, you'll understand that my grasp of this is flimsy to say the least but as I understand things, birds can smell fewer distinct smells than humans can, but they are able to smell different things, the things that are most important to them. I can only think that it's like being able to see in infra-red or ultra-violet. They can smell odours that are so far out of our range of experience that we don't even know they exist – because we can't detect them. It's all a bit baffling for the likes of me but I understand enough to know that it's impressive.

Taste

Taste is closely linked to the smell sense. To prove this for yourself, try holding your nose closed and eating something fragrant like, for example, an orange. It'll taste much blander than usual but if you then let go of your nose, you'll get a sudden 'taste' explosion in your mouth. That's smell and taste combined.

For birds, the sense of taste is not massively important. Given the things that some of them eat, that's not too surprising. People have around 10,000 taste buds, mostly in our tongues. Most birds have less than 500, with very few on the surface of their tiny tongues. Most of theirs are placed around the inner walls of their mouths. But just because their ability to taste their food is less developed than our own, that's not to say they have none at all. If you ever get the chance, try to see an owl eating a slug when there's no rodents to be found. One look at the disgust on its face will convince you that yes, birds do have a sense of taste.

Incidentally, here's a little tip for those of you who don't like the neighbourhood squirrels eating the food that you've put out for 'your' birds. Simply throw a hefty handful of chilli or curry powder into the mix. The squirrels absolutely hate the spicy stuff but the birds can't taste it so won't be bothered by it at all. They'll have all the food to themselves. Of course you'll have to live with the fact that Tufty and his family are now going hungry and it's all your fault...

The Sixth Sense?

We're going back to migration for this one. It's 'a well known fact' that migrating birds use some kind of unknown sixth sense to help them navigate when they take those big journeys twice a year. Don't they?

Well scientists now believe that they probably don't, no. They're not really certain on the percentage of importance of the senses but the evidence suggests that migratory birds use their sight to recognise big physical landmarks along their journey, they hear each other calling so that they all stay together on their flights, and they use their sense of touch to feel the earth's magnetic fields. A special chemical in their retinas allows them to see these magnetic fields to a degree as well. They can see polarised light too, which possibly aids in seeing the magnetic lines at dawn and dusk.

It's also thought that they can track the smell of other birds of their own kind that have flown the same path previously. As I mentioned last week, most birds' sense of smell is generally poor, but in this one specific field it's developed well enough. You can just imagine it...

“Are you sure we're going the right way, love?”

“Yes, I can smell your Uncle Stan from here.”

So from all that we can see how a migrating bird doesn't really have a so-called sixth sense at all, it just combines its five conventional senses and uses whatever information it gathers from those. It is able to work out just enough for its migration navigation needs and no more. That's evolution in action. Isn't it brilliant?

Right, that's enough of the two-part biological malarkey. All this sensory overload is making my brain hurt. Next week we're back to the stand-alone blogs, with a piece about a bird that's strangely related to James Bond. Seriously. Clue, it's been seen on the Old Moor reserve almost every day since Christmas. See if it's on the current sighting list...