The phoebes are still chasing each other incessantly, but, at least on this occasion, one of the birds paused for a few moments to show me, in no uncertain terms, that they're doing more than engaging in avian aerobics. I don't know where the proposed nest might be, but the bird in the lens was clearly coming home with appropriate building materials for the nursery. While the sexes are hard to tell apart, this one is most likely a female, since Eastern Phoebe moms typically construct their mud-and-stick nests on their own, without help from their mates. (The guys are not entirely useless, and usually provide food for their incubating mates.) Build well, mom.