This is the second time that this story appeared in an English translation, its first being by Random House. It's basically the original version of the cartoon show episode where Papa Smurf creates a growth formula that accidentally mutates a plant which he has to dispose. Two Smurfs who are sent to dispose of the formula end up throwing it down into a ravine, where it mutates a baby bird into a deadly predator that goes after the Smurfs. Most of the story is spent with the Smurfs finding a way to bring the bird back to normal or at least down to a size where it can't threaten anyone.
Notably Smurfette doesn't appear in this version of the story, as this was written during a time when Smurfette was introduced as a guest appearance in the Smurf comic books and wouldn't become a permanent resident among the Smurfs until "The Baby Smurf". However, Gargamel does have a small appearance in the story, which the cartoon show episode wisely avoided as his appearance doesn't really add anything to it.
While the story is entertaining, my least favorite part of it in either English edition (Grouchy's "me, I don't like..." from the Papercutz edition notwithstanding) is the gag where a single Smurf has to go through the entire story being stuck wearing a towel, and when Papa Smurf has to do a bullfight with the Howlibird when it's stripped of its feathers, the village leader takes that poor Smurf's towel to do so.
Besides the main story, this book also has "The Smurf Express", where Handy builds a train to help the Smurfs ease the burden of delivering goods collected from the forest into the Smurf Village. Of course, Gargamel comes along and uses this invention against the Smurfs. This story idea also appeared in the cartoon show.