Duck flock with different social groups? - Duck behavior Question

[Peter_Rabbit_Farm]

I have 16 ducks and they all seem to have their own little social group within the flock. They all live in the same coop, but when I let them out to run around they all split up into separate groups and stay like that until I put them back in their coop. All my ducks at different ages and got them at different times. Here are the following groups. I am bringing this up because I am just curious why my ducks do this.

The first group has the ducks that are:
-4 years old
-Khaki Campbells
-2 Drakes / 2 Hens

The second group is:
-3year/2year old ducks
- 4 Peking / 2 Khaki Campbell
- 2 Drakes / 4 Hens

The third group is:
- 2 years old
- Musckovy
- 2 Hens

The Last group:
- 3 months old
- peking/Ancona
- Don't know the sex yet

Is it normal for all my ducks to separate into groups.

 

[fatty and friends]

ducks stay with their “best friends” just like people, my two older drakes stay with each other 24/7 and my other drake follows his two girls around the yard all day

 

[Luv Ducks]

I have 16 ducks and they all seem to have their own little social group within the flock. They all live in the same coop, but when I let them out to run around they all split up into separate groups and stay like that until I put them back in their coop. All my ducks at different ages and got them at different times. Here are the following groups. I am bringing this up because I am just curious why my ducks do this.

The first group has the ducks that are:
-4 years old
-Khaki Campbells
-2 Drakes / 2 Hens

The second group is:
-3year/2year old ducks
- 4 Peking / 2 Khaki Campbell
- 2 Drakes / 4 Hens

The third group is:
- 2 years old
- Musckovy
- 2 Hens

The Last group:
- 3 months old
- peking/Ancona
- Don't know the sex yet

Is it normal for all my ducks to separate into groups.

This seems to be quite normal. I had two Mallards I got from California that were always together in the pen, two Rouens that I got together from my Boss, two mallards that were given to me by a friend that would not leave each other and two that hatched out here at my house that never left each others side. The would all come out of the pen to free range together but still pair up. They like having their best friend by their side, just like some of us people, lol.