The birds did the trick for a little while, but soon enough the Whomping Willow was back to doing its usual thing of being restless and swaying its beaches every which way. It's a good thing that your potion is coming along because you are definitely not welcome company in its eyes.

As the vial is summoned from one of the branches, the tree tries to THRASH it with one of its limbs, but fortunately for you it doesn't work. Your potion is done, ingested, and you are ready to go!

Just make sure not to get hit by any of those branches as you make your way towards the trunk; that could do some real damage despite the shield.