In which country is whistling considered bad luck?

Answer 1

Not so much bad luck but in Slavic countries it is said to bring poverty. And in other countries pest animals like mice or snakes.

Whistling on-stage is considered very bad luck indeed.

Answer 2

..from http://customsholidays.suite101.com/article.cfm/whistling__a_dying_art In many cultures whistling has never been appreciated. In India, for instance, whistling is as rude as winking or touching someone with your shoes or feet. Also in Russia, whistling in public is as bad as showing soles of the shoes when sitting. In Korea it is considered bad luck, especially when done by women. Also among Muslims, whistling is frowned upon, because it might attract demons. In an older Europe, whistling could be bad luck, on ships for instance (on a par, I guess, with bringing a woman on board). In Goethe's Faust, the angels sang, but the Devil whistled.

Answer 3

My Grandfather used to recite an old poem, "A whistling woman and a crowing hen, both will come to some bad end."

I have also heard of old superstitions of people whistling up the wind.