Second poll is retarded. There is no way to provide a forecast, especially since previous forecasts have been wrong (for example Muslim share of French population has almost doubled between the 1999 and 2009 census, whereas it was forecast to grow some 40%.) Also, it provides no room for shocks, such as a million Muslims coming into Germany from nowhere, and this could not be accounted for in 2007.
As for the first poll, the easiest explanation is the fact that minorities tend to be in cities, and they also tend to be younger. Most people don’t think of rural areas or small towns, and they certainly don’t think of the elderly who don’t really go out.
It’s very easy to think 40% of your country is Muslim when you’re French when more than half of Paris isn’t French. In terms of perception, Muslims is pretty much most of what you see in places like Marseilles and it’s pretty much all of what you see in places like Calais. People’s perceptions are derived from visual images, and when people imagine Paris they don’t think of 18 white Frenchmen and 2 Berbers.
If I go out to my city centre I find it hard to describe my city as more than half white British, even though I know statistically it’s one of the whitest cities in the UK at 90%, far above national average. Statistics are widely different from visual anecdotes. It’s just that many of these whites in my city live in suburban areas and not the centre, and many shop online, and many are elderly and don’t go out, and there’s certainly fewer white under 20s. So the perception is then that most aren’t white.