Carrie- not to move in on jenifert's subject, but I have a similar problem with my dog, Scout. She is REALLY good with my cats, but any little animal running around outdoors is a different story. She is very well behaved most of the time, and will come when called, etc......but when she is chasing something outdoors, she seems a bit out of control.
She is B. Collie/Lab mix, 3 yrs. old.
She has gone through basic obedience, and done very well.

I guess my question is: What kind of whistle? Just a regular type sports whistle?
And also, what do you think of clicker training?