Mysterious House Sparrow Calls

I made a more valiant effort today to get to know my bird of the week and actually spent some time out on the porch watching sparrows. I saw some quick indirect scratching, bill wiping, and other behaviors. But the more I watched, the more puzzled I became. It was clear that I had no idea what these birds are doing out there. At one point there was a male up in the top of a holly tree, calling fairly consistently with some type of a "cheep" call, while a female hoped around in a slightly lower branch making some kind of a lower pitched "churr" call. When I got a better look at the female it was clear she had something in her beak, so I thought she might be carrying food to young in a nest. But she stayed up there churrping and moving about repeatedly for over 15 minutes. Eventually the male flew off to land on the ground in a neighbor's yard. I never did figure out what the female was up to.

As I listened to the sparrow calls, I could tell that there were many different types of subtle differences in the calls, but it was tough to focus on them. Afterwards, I went to xeno-canto.org to listen to House Sparrow calls and the mystery deepened. Paul Driver's bird calls website gave me more samples to listen to, but I am still left scratching my head. I guess I've known forever that House Sparrows make a lot of different sounds, but I never paid them any attention. And now that I'm trying to sort them out, it is a bit bewildering. So much to learn, so much I don't know about these common little neighbors in my yard!