ok. Lets try again.
So you have some string values provided by the user say : Babbler, Sparrow and Crow. You want to check if any or all? Babbler, Sparrow and Crow values exists in a field called birds in your input feature class. Is this correct?
How do users provide these values. A separate variable for each user input, meaning a variable for Babbler, another separate variable for Sparrow and so on? or the user provides these values in a single multivalue variable?
You want to check if a particular value exists in a field????