What kind of bird is this? It has built its nest in my girlfriend's air conditioning hole.

According to the information you provided, this bird may be a mercerized starling. Mercerized starling is a common bird, which often nests in holes in the wall. When they nest indoors, it may have some impact on residents' lives, such as noise interference, smell and so on.

If you want to solve this problem, here are some suggestions:

1. Observe the Bird's Nest: First, you can observe the situation in the Bird's Nest. If there are young birds in the nest, it is best not to touch or move the nest, so as not to hurt the young birds or cause panic reaction of parents.

2. Block air conditioning holes: If you don't want birds to nest indoors, you can try to block air conditioning holes or other possible entrances with materials such as foam. This can prevent birds from entering the room without hurting them.

3. Gently move the bird's nest: If you want to move the bird's nest, you can gently take it out and put it at an appropriate distance outdoors. Remember to operate carefully so as not to disturb parents or young birds.

4. Seek professional help: If you are not sure how to deal with this situation, or need more advice and help, you can consult the local wildlife protection agency or animal protection organization.

No matter which method is adopted, we should try our best to avoid causing harm to birds, and at the same time, we should respect their right to survival and natural behavior.