They are all vertebrates: Females have two lateral vaginas, which lead to separate uteruses. A third canal, the median vagina, is used for birth. Males have a two-pronged penis, which corresponds to...
I am not sure what level answer you are looking for, I will assume basic. Mammals and birds are both warm blooded and are both vertebrate animals (have a backbone). Hope that helps.
Just think of any property that you don't have and your dog or a tree does't. There you go. E.g. a tail, chlorophyll... You probably should be more specific.