Well, the first 2 are talking about birds but the first one is talking about how Tim's parrot learned to speak faster than Mr. Riley's parrot did. The second one is talking about Some one wondering if parakeets were more popular than parrots as a pet. The last one is talking about one pet store being better than the other. The last one could be referring to purchasing Parrots or parakeets at the pet store. Overall I think the comparison between all of them is that they're referring to some type of pet.
Hope this helps.
