It depends, I can whistle through my front teeth and its not like they are strangely spaced.
You do not even need your lips to whistle. They actually produce poorer quality pitches than if you don't use your lips. You use your tongue and arc it up/down to change the pitch of the whistle and push a tight hole of air through your teeth.
Lips
Air travels through the whistle rubbing against the sides of the whistle than being forced out of the smaller opening at the front. The friction of air against the sides of the whistle is what makes the noise.
No, it couldn't, because chickens don't know how to whistle!
In my opinion, if the chicken had lips, then yes, it could whistle. But then again, how would it learn to whistle? Someone would have to teach it. And why would a chicken want to whistle anyway? To show off to the other birds? Or maybe it would cheer him up on a gloomy day. . . nah! Could a chicken whistle if it had lips? I guess the world will never know. . .
LIP
Gives you sore lips?
To blow a whistle, put your lips together and blow air through them while holding the whistle in front of your mouth. The sound will be produced by the air vibrating inside the whistle. Make sure to adjust the pressure and intensity of your blowing to control the pitch and volume of the whistle sound.
Practise, practise and more practise, when you get bored from failing so much, buy a Whistle.
Yes, "whistle" can be a verb when it refers to the act of making a high-pitched sound by blowing air through pursed lips or a small hole. For example, "She whistled a tune as she walked down the street."
That is the correct spelling of "whistle" (a sound or a noisemaker, or to make sound or music with the lips).
Chickens do not have the anatomical structure to produce whistling sounds like humans do. Even if a chicken had lips, it's unlikely that they would be able to whistle in the same way humans can.