Piper recognizes that the bird men are not extraplanar, but are subterranean. Known as dire corbies, they are flightless, have a look much like a humanoid crow, and fight with sharp claws (not talons). As far as hunting and fighting goes, they are pouncers with a surprising leap. They do not have any particularly stout defenses, as far as he can recall, but they are pretty ferocious, exhibiting a lot of stamina in a fight.
The corbies walk down the road, not particularly cautious, but their heads seem to twitch and turn back and forth, much like a regular bird's does. And it isn't long before they spot Masamune among the foliage on the left side of the trail (from their perspective). They cry out in surprise before hissing in anger and malice.
Initiative for everybody. Nobody but Masamune has been spotted yet. That gives the rest of you the option of surprising the dire corbies. Normally, surprise happens before a fight starts in earnest with surprising characters taking a single action (standard or move), but if you want to delay for a while to preserve the surprise, I"m going to let you take a regular round's worth of actions and still benefit from the surprise conditions (flatfooted enemies, etc) when you finally jump in. This may be useful if you want the corbies to close a bit more before revealing your presence...
Alara: 1d20 + 3 ⇒ (3) + 3 = 6
Ash: 1d20 + 1 ⇒ (17) + 1 = 18
Masamune: 1d20 + 3 ⇒ (4) + 3 = 7
Piper: 1d20 + 2 ⇒ (2) + 2 = 4
Rawnie: 1d20 + 1 ⇒ (19) + 1 = 20
Dire Corbies: 1d20 + 1 ⇒ (14) + 1 = 15
Alara, Ash, Piper, and Rawnie all of the option of going before the corbies with a single action, truly initiating an ambush.
Otherwise, the initiative will be Ash and Rawnie, Corbies, Alara, Masamune, and Piper.
From the point where they are in the road, the dire corbies start to move forward to close the gap with Masamune, not knowing there are hidden adventurers ready to get the drop on them...