Suggestions regarding new dog & other pets

I need some advice. My SIL recently moved in with us & has been talking about getting a dog. So a couple of days ago, she decided to get a cocker spaniel from a friend of hers. So far he's working out things with our 2 dogs (Akita mix & husky/malamute mix) and the 4 cats are in hiding. What I'm slightly concerned about is his reaction to our smaller animals. He comes from a dog-only household & hasn't been exposed to other critters. We have 2 birds & 2 guinea pigs in wire cages and 3 degus in a big aquarium (I don't think they'll be an issue since it's glass & up higher than the other cages). What he's been doing is getting up on his hind legs & scratching at the cages. The guinea pigs could apparently care less, but he's totally flipping out my birds and, in both instances, setting off the other 2 dogs to barking. Plus, I'm afraid he's gonna knock the cages off their stands since they're so light-weight. Any ideas on how to handle this? If this is just a new dog adaptation thing, how long will it take him to settle in? My SIL has a crate for him at night or when no one is home, but otherwise I'd like him to have the same freedom in thehouse as our dogs. He's loose upstairs this afternoon with the birds in the girls' room (there isn't enough room in there for that to work full-time, though) and a gate to keep him away from the guinea pigs, although he can still see them. Does it seem like this is the best solution or is there anything else I can do?

Sounds like he is just curious of your little critters. While it is never a good idea to leave little critters alone with any animal that could even accidentally hurt them I do not think he intends to do so. My suggestion would be to hang your bird cage from the ceiling or put them on a higher shelf. And as for the guinea pigs I would get them a cage with out a stand . I keep my rats in a three tier cage on a table in our dinning room (not the dinner table). Also every time you see him doing this tell him NO is a firm voice. If he walks by the cage without a second look tell him how good he is. EVERYONE in the house must participate in this so he won't get confused. If that does not work get a spray bottle or a bottle of compressed air if you don't want a wet doggy. The compressed air does not hurt them it only surprises them and they don't like the sound. If he tries to get the cage spray his hind quarters (never his face) with it. This simulates another dog (his mother maybe or pack leader) telling him no. That his actions are not acceptable. Feed your smaller critters first in front of the dog (birds then guinea pigs then cats then him) let him see that they get to eat first. This tells him that they are higher then him as far as pack dynamics go so not to bother them and to respect them.