How come Fearow isn't vulnerable to rock?

Question

I used rock slide on my friend's Fearow and it wasn't super effective. It wasn't holding any special item so what was it?

Answer 1

The only explenation for that is Fearow used Roost which temporarely negates the Flying types weaknesses.
Including Rock weankess yes.

Comments

Fearow did use roost and I didn't know it did that.

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To be more precise it actually removes the flying type temporarily (the same turn), which means it can be hit by ground moves :P

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