Wednesday, 29 January 2014

Avoiding snarge

Have you ever come across the word “snarge”? If you have not and you have a delicate stomach, then STOP READING RIGHT NOW. 
Snarge is the remains of birds that have collided with aircraft — the bits of flesh and feather, blood and beak that are left smeared across a plane after a bird-strike. No one is sure where the term originated, but it is certainly an evocative expression.
The study of snarge is important in ensuring air safety, since collisions with birds can lead to planes crashing. A well-known incident occurred in January 2009 when a plane taking off from New York’s La Guardia airport hit a flock of Canada Geese at an altitude of about 3,000ft. The pilots saw their windscreen turn dark brown and heard several loud thuds. Then the engines died and the cockpit was filled with the aroma of barbecued wildfowl. The plane ditched in the Hudson River — luckily without loss of human life. However,  worldwide more than 150 people have died as a result of bird strikes over the past 20 years or so.
When a bird strike occurs, air accident investigators need to determine the species involved so that they can work out ways of keeping the birds and the planes apart, in the interest of both air safety and the survival of the species involved. They therefore sample the snarge so that the birds can be identified. The standard collection technique involves spraying the besnarged area with water and wiping it with a clean rag or paper towel, which is then sent away for analysis. 
In the US, some 4,000 snarge samples a year are sent to the Feather Identification Laboratory at the Smithsonian Institution’s National Museum of Natural History in Washington, DC. When whole feathers can be retrieved, they are matched against the specimens in the museum's collections. When feather remains are too severely damaged for naked-eye identification, microscopes are brought out and the snarge is compared with thousands of slides of feather barbs. And if there is not enough feather even for microscopic comparison, DNA is extracted from the snarge and matched to a database of DNA records from tens of thousands of species.

Tuesday, 28 January 2014

A quackpot myth

On 7 February 2014, a new television comedy panel game show begins (or began, depending on when you are reading this) on Sky1, presented by Lee Mack, one of my favourite comedians. In each of the eight episodes, three celebrities aided by in-house boffins present weird “facts” and attempt to prove whether they are true.

The title of the show is Duck Quacks Don’t Echo. This is a reference to a popular belief that, er, duck quacks don’t echo.

The idea that the quacking of a duck does not reverberate, and that nobody knows why, has been widely repeated by such authoritative sources as Twitter feeds, online blogs, email trivia lists and even fruit drink bottle caps. The concept is, of course, completely quackers. Why on earth would the call of a duck be exempt from the acoustic laws that apply to all other sounds? 

But the myth is not so crackers that it has been ignored by academic researchers. I learnt recently that a few years ago acoustics scientists at the University of Salford investigated this fantasy with the co-operation of a duck called Daisy (species not disclosed, but presumably a farmyard-type Mallard), which they had recruited from a Cheshire farm. (I have no idea who was stupid enough to fund the research.) 

When Daisy was recorded quacking in an anechoic chamber and also in a reverberation chamber, it turned out that there was no echo in the former (which is, of course, why it is called anechoic) but a reverberant echo in the latter. Surprise, surprise!

If you wish, you can listen to samples of Daisy Duck’s various echoic and anechoic quacks at

Sadly, shortly after the university relieved Daisy of her scientific duties and returned her to her farm, she became dinner for a local fox and has therefore quacked no more. 

But how did the quackpot duck-quacks-don’t-echo myth arise? 

One theory is that although quacks may echo, ducks rarely loiter near suitable reflective surfaces. An echo is only generated if there is a nearby smooth surface, such as a cliff face, positioned at an appropriate angle to bounce the sound back to the listener. 

A second theory is that because quacking ducks — such as female Mallard and Gadwall — tend to quack fairly quietly, their echoes are too quiet to hear.