Hi Yossarian , and welcome to the forum. Great name for a chipmunk Yossarian .

He does sound like he's behaving like a female, as the only time my males make a noise is if they are frightened by something or they are communicating with another from another room. But although loud and a bit like a bird, the alarm call is repeated quicker than the mating call and does not go on all day. Mine like looking out the window, and we had a male bird of pray roosting on the telecome tower. My chipmunks knew it was a threat, or thought it was, so off would go the alarm call, then some of the others would join in.
I think they can communicate over long distances, bit like whales, as part of the sound they make is on a frequency we can't hear. So as mum is only 100mtrs away perhaps they are just chatting.
There is one other sound I hear them make, it's a very soft plaintive call, like they are whimpering. When I first heard that sound i thought one of them was trapped or in pain. It's so soft that it's hard to know quite where the sound is coming from, unlike their alarm sound.