1. Simon Marquis, chairman, ZenithOptimedia UK
Marquis objects strongly to the term "twitcher". Apparently, twitchers are people who think nothing of trekking miles to get a mere glimpse of a bird they've not seen before. Marquis assures us he is neither this dedicated or this anal. He also denies rumours that he once held up a golf match at Wentworth by sneaking off into the rough to spot a sparrow or two.
2. Russell Boyman, ex of Ogilvy & Mather
Boyman is the only person on this list to have made some decent money out of his hobby. After leaving O&M, Boyman wrote a bestseller entitled Around the World With a 1,000 Birds. For those who share his passion, Boyman's book is available in all good internet book shops.
3. Paul Longhurst, managing director, The Allmond Partnership
Like Marquis, Longhurst would also have us believe that he's not a serious twitcher. We think he's just being modest. He says that he merely knows the difference between a sparrow and a sparrow hawk. We say: "That's good enough for us, you're in the list."
4. Richard Burdett, acting head, 4creative
In twitching terms, Burdett is hardcore. The former vice-president of CIA UK is more than prepared to sit in a Norfolk shed for days at a time in the hope that something special will shoot past his binoculars.
5. Neil Wallis, deputy editor, News of the World
It's a slightly obvious joke to make, but you'd have thought that the only birds Wallis would be prepared to goggle at were the ones that regularly appear half-naked in his newspaper. But it seems there's more to Wallis than meets the eye. When he's not exposing the secrets of the famous, the former editor of the People is admiring the plumages of the lesser-spotted.
6. Martin Sambrook, global account director, Media Audits
Sambrook is another who is keen to play down his fascination with winged things. But believe us, when media gets too much for him, his mind turns to birds.
7. Jim Lawrence, ex of Ogilvy & Mather
The former Ford account man is as keen an ornithologist as you could ever hope to meet. Using Marquis' definition, Lawrence is a true twitcher. In the days before mobile phones he used to own a pager that would keep him abreast of rare sightings. If a particularly unusual species were to be spotted in the Outer Hebrides, Lawrence would hear about it within seconds, and be in his car and on the motorway before you could say "yellow-bellied sapsucker."
8. David Byles, chief executive, MindShare Latin America
Byles used to be the media director at JWT in London. The pigeons of Trafalgar Square must have been to dull for him - he's since moved to Mexico, home to 1,060 of the world's 8,500 species.
9. Nick Blair, ex-managing director, Dorlands
This entry is a bit cheeky. Blair does watch birds, but only as a prelude to blowing them out of the sky with his huntsman's rifle.
10. Toby Hoare, chairman, Bates
See Nick Blair.