Guinea pig bird noise?

[Togepi]

One of my boys has made a bird noise 2 or 3 times over the past week since I put them all in their C&C cages next to each other.

Is the bird noise normal, I dont know of any other way to explain it but when I go in the room he is laying down making a chirping noise.

I've put him in a cage thats attached to his brothers cage (previously separated as they didnt get on) and they are really enjoying each others company... or so I thought.

Is this a distress call? Is he unhappy in anyway?

 

[Toffeewoffee]

No one is really sure what it means, it is very rare for piggies to do it, so you should be privalleged (i know that is spelt wrong but got brain freeze)

One of my girls does it sometimes, though not for a long time now.

But it is a mystery as to what it means, did you notice is being at a particular time of day?

My girl only ever did it at dusk when things were quiet and just starting to get light, but as soon as she heard or sore movement it stopped (i was trying to get my phone to record it)

 

[Guinea pig slave]

Two of my girls have done this - it's beautiful to hear but it worried me that something had upset them
http://www.guinealynx.info/behavior.html#chirping
No one can give 100% true reason as to why they do it - my girls just stand on their upper level in the pen and chirp whilst the others just carry on doing what they're doing rolleyes
If they do it, I just check they're ok