adding gunnies to a year old flock

If you're talking about guineas, those silly birds with the pointy heads, I've kept mine with chickens with no problems. My guineas like the highest perch and run around in their own flock while the chickens prefer the lower perches and also run around in their own flock. Just be sure you don't let them free range for a few weeks so they know to come back to the coop at night rather than perch in trees.

The only "Gunnies" I know anything about are Marine Corps Gunnery Sargeants. They don't get along well with others.

Very funny, NYReds.

Guineas do better in their own society. I had four of them, raised from the time they were six weeks old in the coop with the chickens. Even after free ranging with the chickens, as they approached mating age, the alpha male began attacking one of the RIR hens. Then, the other three joined in on attacks on the other two RIR hens. It was a constant battleground and I ended up rehoming the guineas. Mine were very tame, too, and I miss them, but it wasn't all rainbows and roses with them living together. I'll do it again one day, but will have a larger number of guineas and they'll live separately from the chickens.

That's interesting. Mine have never attacked my chickens. I've never had fewer than 6 with my chickens. I've only got 5 guineas right now but am getting more in May and hope to hatch some eggs once they start laying again. Haven't got any chickens at the moment. Next week I get more chicks so I will see if everything continues to run smoothly here.

Here is a picture of my alpha male attacking my BR rooster. They only attacked the RIR hens and the BR rooster.

Mine get along just fine, they do take teh highest roost but they cuddle right up with some of the other hens that roost up high also.

Mine got along fine with the chickens they grew up with, too...until they approached mating and laying age. Then it was on like donkey kong. 

Folks who expect guineas to act like chickens are in for a rude awakening. I just want folks to be prepared if it's not all rainbows and roses in the coop when guineas and chickens clash. Guineas are very different animals, they pair up and don't mate indiscriminately like chickens, they are seasonal layers, they are all broody, not just some, they fight by bodyslamming their victims as a pack, etc. Just be prepared if it isn't what you think it will be.

Will they sit on Chicken eggs? I only have two Guinea Hens no Males, my byddy wants to give me one of his males not sure if ill take it.

Yes, they would sit on any eggs, I'm sure, but the way they do it is they let eggs collect until they have a huge clutch, then they start to sit. Guinea eggs take about 28 days to hatch, so you'd have to be sure that they get the chicken eggs a week after they start sitting on their own tight or somehow, remove all their own eggs and replace with chicken eggs so you don't have eggs due a week apart (unless the guinea eggs are not fertile in the first place). Could be a tricky proposition. Maybe someone who has done it can better give you suggestions.