[Well, he was thinking that there were more surprises than just cockatrices likely to be waiting for them, but the boy raises an excellent point.]

The message stated 'Feed the Cockatrice' rather than 'Feed a Cockatrice.' So there may indeed be only one or it may be a specific one, but it would be good to be sure.

[Gandalf strokes his beard in consideration.]

Do you have any companions here who might be recruited to join us? We will cover more ground.

[The message also said a requirement of 2 but not of only 2.]