Definition: In this task, you are given two phrases: Head and Tail, separated with <sep>. The Head and the Tail events are short phrases possibly involving participants. The names of specific people have been replaced by generic words (e.g., PersonX, PersonY, PersonZ). PersonX is always the subject of the event. You have to determine whether the Head is a part, portion, or makeup of the Tail or not. Classify your answers into "Yes" and "No". The phrase may also contain "___", a placeholder that can be an object, a person, and/or an action.

Positive Example 1 -
Input: Head: bed<sep>Tail: mattress
Output: Yes

Positive Example 2 -
Input: Head: PersonX asks ___ to go with PersonY<sep>Tail: follows the other person
Output: No

Negative Example 1 -
Input: Head: PersonX acts weird<sep>Tail: attention
Output: Yes

Negative Example 2 -
Input: Head: war<sep>Tail: aggression
Output: No

Now complete the following example -
Input: Head: flock<sep>Tail: bird
Output: Yes